Merge tag 'v4.10-rc5' into for-linus

[GitHub/LineageOS/android_kernel_motorola_exynos9610.git] / drivers / gpu / drm / i915 / intel_fbc.c

/*
 * Copyright © 2014 Intel Corporation
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice (including the next
 * paragraph) shall be included in all copies or substantial portions of the
 * Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 * DEALINGS IN THE SOFTWARE.
 */

/**
 * DOC: Frame Buffer Compression (FBC)
 *
 * FBC tries to save memory bandwidth (and so power consumption) by
 * compressing the amount of memory used by the display. It is total
 * transparent to user space and completely handled in the kernel.
 *
 * The benefits of FBC are mostly visible with solid backgrounds and
 * variation-less patterns. It comes from keeping the memory footprint small
 * and having fewer memory pages opened and accessed for refreshing the display.
 *
 * i915 is responsible to reserve stolen memory for FBC and configure its
 * offset on proper registers. The hardware takes care of all
 * compress/decompress. However there are many known cases where we have to
 * forcibly disable it to allow proper screen updates.
 */

#include "intel_drv.h"
#include "i915_drv.h"

static inline bool fbc_supported(struct drm_i915_private *dev_priv)
{
        return HAS_FBC(dev_priv);
}

static inline bool fbc_on_pipe_a_only(struct drm_i915_private *dev_priv)
{
        return IS_HASWELL(dev_priv) || INTEL_GEN(dev_priv) >= 8;
}

static inline bool fbc_on_plane_a_only(struct drm_i915_private *dev_priv)
{
        return INTEL_GEN(dev_priv) < 4;
}

static inline bool no_fbc_on_multiple_pipes(struct drm_i915_private *dev_priv)
{
        return INTEL_GEN(dev_priv) <= 3;
}

/*
 * In some platforms where the CRTC's x:0/y:0 coordinates doesn't match the
 * frontbuffer's x:0/y:0 coordinates we lie to the hardware about the plane's
 * origin so the x and y offsets can actually fit the registers. As a
 * consequence, the fence doesn't really start exactly at the display plane
 * address we program because it starts at the real start of the buffer, so we
 * have to take this into consideration here.
 */
static unsigned int get_crtc_fence_y_offset(struct intel_crtc *crtc)
{
        return crtc->base.y - crtc->adjusted_y;
}

/*
 * For SKL+, the plane source size used by the hardware is based on the value we
 * write to the PLANE_SIZE register. For BDW-, the hardware looks at the value
 * we wrote to PIPESRC.
 */
static void intel_fbc_get_plane_source_size(struct intel_fbc_state_cache *cache,
                                            int *width, int *height)
{
        int w, h;

        if (drm_rotation_90_or_270(cache->plane.rotation)) {
                w = cache->plane.src_h;
                h = cache->plane.src_w;
        } else {
                w = cache->plane.src_w;
                h = cache->plane.src_h;
        }

        if (width)
                *width = w;
        if (height)
                *height = h;
}

static int intel_fbc_calculate_cfb_size(struct drm_i915_private *dev_priv,
                                        struct intel_fbc_state_cache *cache)
{
        int lines;

        intel_fbc_get_plane_source_size(cache, NULL, &lines);
        if (INTEL_GEN(dev_priv) == 7)
                lines = min(lines, 2048);
        else if (INTEL_GEN(dev_priv) >= 8)
                lines = min(lines, 2560);

        /* Hardware needs the full buffer stride, not just the active area. */
        return lines * cache->fb.stride;
}

static void i8xx_fbc_deactivate(struct drm_i915_private *dev_priv)
{
        u32 fbc_ctl;

        /* Disable compression */
        fbc_ctl = I915_READ(FBC_CONTROL);
        if ((fbc_ctl & FBC_CTL_EN) == 0)
                return;

        fbc_ctl &= ~FBC_CTL_EN;
        I915_WRITE(FBC_CONTROL, fbc_ctl);

        /* Wait for compressing bit to clear */
        if (intel_wait_for_register(dev_priv,
                                    FBC_STATUS, FBC_STAT_COMPRESSING, 0,
                                    10)) {
                DRM_DEBUG_KMS("FBC idle timed out\n");
                return;
        }
}

static void i8xx_fbc_activate(struct drm_i915_private *dev_priv)
{
        struct intel_fbc_reg_params *params = &dev_priv->fbc.params;
        int cfb_pitch;
        int i;
        u32 fbc_ctl;

        /* Note: fbc.threshold == 1 for i8xx */
        cfb_pitch = params->cfb_size / FBC_LL_SIZE;
        if (params->fb.stride < cfb_pitch)
                cfb_pitch = params->fb.stride;

        /* FBC_CTL wants 32B or 64B units */
        if (IS_GEN2(dev_priv))
                cfb_pitch = (cfb_pitch / 32) - 1;
        else
                cfb_pitch = (cfb_pitch / 64) - 1;

        /* Clear old tags */
        for (i = 0; i < (FBC_LL_SIZE / 32) + 1; i++)
                I915_WRITE(FBC_TAG(i), 0);

        if (IS_GEN4(dev_priv)) {
                u32 fbc_ctl2;

                /* Set it up... */
                fbc_ctl2 = FBC_CTL_FENCE_DBL | FBC_CTL_IDLE_IMM | FBC_CTL_CPU_FENCE;
                fbc_ctl2 |= FBC_CTL_PLANE(params->crtc.plane);
                I915_WRITE(FBC_CONTROL2, fbc_ctl2);
                I915_WRITE(FBC_FENCE_OFF, params->crtc.fence_y_offset);
        }

        /* enable it... */
        fbc_ctl = I915_READ(FBC_CONTROL);
        fbc_ctl &= 0x3fff << FBC_CTL_INTERVAL_SHIFT;
        fbc_ctl |= FBC_CTL_EN | FBC_CTL_PERIODIC;
        if (IS_I945GM(dev_priv))
                fbc_ctl |= FBC_CTL_C3_IDLE; /* 945 needs special SR handling */
        fbc_ctl |= (cfb_pitch & 0xff) << FBC_CTL_STRIDE_SHIFT;
        fbc_ctl |= params->fb.fence_reg;
        I915_WRITE(FBC_CONTROL, fbc_ctl);
}

static bool i8xx_fbc_is_active(struct drm_i915_private *dev_priv)
{
        return I915_READ(FBC_CONTROL) & FBC_CTL_EN;
}

static void g4x_fbc_activate(struct drm_i915_private *dev_priv)
{
        struct intel_fbc_reg_params *params = &dev_priv->fbc.params;
        u32 dpfc_ctl;

        dpfc_ctl = DPFC_CTL_PLANE(params->crtc.plane) | DPFC_SR_EN;
        if (drm_format_plane_cpp(params->fb.pixel_format, 0) == 2)
                dpfc_ctl |= DPFC_CTL_LIMIT_2X;
        else
                dpfc_ctl |= DPFC_CTL_LIMIT_1X;

        if (params->fb.fence_reg != I915_FENCE_REG_NONE) {
                dpfc_ctl |= DPFC_CTL_FENCE_EN | params->fb.fence_reg;
                I915_WRITE(DPFC_FENCE_YOFF, params->crtc.fence_y_offset);
        } else {
                I915_WRITE(DPFC_FENCE_YOFF, 0);
        }

        /* enable it... */
        I915_WRITE(DPFC_CONTROL, dpfc_ctl | DPFC_CTL_EN);
}

static void g4x_fbc_deactivate(struct drm_i915_private *dev_priv)
{
        u32 dpfc_ctl;

        /* Disable compression */
        dpfc_ctl = I915_READ(DPFC_CONTROL);
        if (dpfc_ctl & DPFC_CTL_EN) {
                dpfc_ctl &= ~DPFC_CTL_EN;
                I915_WRITE(DPFC_CONTROL, dpfc_ctl);
        }
}

static bool g4x_fbc_is_active(struct drm_i915_private *dev_priv)
{
        return I915_READ(DPFC_CONTROL) & DPFC_CTL_EN;
}

/* This function forces a CFB recompression through the nuke operation. */
static void intel_fbc_recompress(struct drm_i915_private *dev_priv)
{
        I915_WRITE(MSG_FBC_REND_STATE, FBC_REND_NUKE);
        POSTING_READ(MSG_FBC_REND_STATE);
}

static void ilk_fbc_activate(struct drm_i915_private *dev_priv)
{
        struct intel_fbc_reg_params *params = &dev_priv->fbc.params;
        u32 dpfc_ctl;
        int threshold = dev_priv->fbc.threshold;

        dpfc_ctl = DPFC_CTL_PLANE(params->crtc.plane);
        if (drm_format_plane_cpp(params->fb.pixel_format, 0) == 2)
                threshold++;

        switch (threshold) {
        case 4:
        case 3:
                dpfc_ctl |= DPFC_CTL_LIMIT_4X;
                break;
        case 2:
                dpfc_ctl |= DPFC_CTL_LIMIT_2X;
                break;
        case 1:
                dpfc_ctl |= DPFC_CTL_LIMIT_1X;
                break;
        }

        if (params->fb.fence_reg != I915_FENCE_REG_NONE) {
                dpfc_ctl |= DPFC_CTL_FENCE_EN;
                if (IS_GEN5(dev_priv))
                        dpfc_ctl |= params->fb.fence_reg;
                if (IS_GEN6(dev_priv)) {
                        I915_WRITE(SNB_DPFC_CTL_SA,
                                   SNB_CPU_FENCE_ENABLE | params->fb.fence_reg);
                        I915_WRITE(DPFC_CPU_FENCE_OFFSET,
                                   params->crtc.fence_y_offset);
                }
        } else {
                if (IS_GEN6(dev_priv)) {
                        I915_WRITE(SNB_DPFC_CTL_SA, 0);
                        I915_WRITE(DPFC_CPU_FENCE_OFFSET, 0);
                }
        }

        I915_WRITE(ILK_DPFC_FENCE_YOFF, params->crtc.fence_y_offset);
        I915_WRITE(ILK_FBC_RT_BASE, params->fb.ggtt_offset | ILK_FBC_RT_VALID);
        /* enable it... */
        I915_WRITE(ILK_DPFC_CONTROL, dpfc_ctl | DPFC_CTL_EN);

        intel_fbc_recompress(dev_priv);
}

static void ilk_fbc_deactivate(struct drm_i915_private *dev_priv)
{
        u32 dpfc_ctl;

        /* Disable compression */
        dpfc_ctl = I915_READ(ILK_DPFC_CONTROL);
        if (dpfc_ctl & DPFC_CTL_EN) {
                dpfc_ctl &= ~DPFC_CTL_EN;
                I915_WRITE(ILK_DPFC_CONTROL, dpfc_ctl);
        }
}

static bool ilk_fbc_is_active(struct drm_i915_private *dev_priv)
{
        return I915_READ(ILK_DPFC_CONTROL) & DPFC_CTL_EN;
}

static void gen7_fbc_activate(struct drm_i915_private *dev_priv)
{
        struct intel_fbc_reg_params *params = &dev_priv->fbc.params;
        u32 dpfc_ctl;
        int threshold = dev_priv->fbc.threshold;

        dpfc_ctl = 0;
        if (IS_IVYBRIDGE(dev_priv))
                dpfc_ctl |= IVB_DPFC_CTL_PLANE(params->crtc.plane);

        if (drm_format_plane_cpp(params->fb.pixel_format, 0) == 2)
                threshold++;

        switch (threshold) {
        case 4:
        case 3:
                dpfc_ctl |= DPFC_CTL_LIMIT_4X;
                break;
        case 2:
                dpfc_ctl |= DPFC_CTL_LIMIT_2X;
                break;
        case 1:
                dpfc_ctl |= DPFC_CTL_LIMIT_1X;
                break;
        }

        if (params->fb.fence_reg != I915_FENCE_REG_NONE) {
                dpfc_ctl |= IVB_DPFC_CTL_FENCE_EN;
                I915_WRITE(SNB_DPFC_CTL_SA,
                           SNB_CPU_FENCE_ENABLE | params->fb.fence_reg);
                I915_WRITE(DPFC_CPU_FENCE_OFFSET, params->crtc.fence_y_offset);
        } else {
                I915_WRITE(SNB_DPFC_CTL_SA,0);
                I915_WRITE(DPFC_CPU_FENCE_OFFSET, 0);
        }

        if (dev_priv->fbc.false_color)
                dpfc_ctl |= FBC_CTL_FALSE_COLOR;

        if (IS_IVYBRIDGE(dev_priv)) {
                /* WaFbcAsynchFlipDisableFbcQueue:ivb */
                I915_WRITE(ILK_DISPLAY_CHICKEN1,
                           I915_READ(ILK_DISPLAY_CHICKEN1) |
                           ILK_FBCQ_DIS);
        } else if (IS_HASWELL(dev_priv) || IS_BROADWELL(dev_priv)) {
                /* WaFbcAsynchFlipDisableFbcQueue:hsw,bdw */
                I915_WRITE(CHICKEN_PIPESL_1(params->crtc.pipe),
                           I915_READ(CHICKEN_PIPESL_1(params->crtc.pipe)) |
                           HSW_FBCQ_DIS);
        }

        I915_WRITE(ILK_DPFC_CONTROL, dpfc_ctl | DPFC_CTL_EN);

        intel_fbc_recompress(dev_priv);
}

static bool intel_fbc_hw_is_active(struct drm_i915_private *dev_priv)
{
        if (INTEL_GEN(dev_priv) >= 5)
                return ilk_fbc_is_active(dev_priv);
        else if (IS_GM45(dev_priv))
                return g4x_fbc_is_active(dev_priv);
        else
                return i8xx_fbc_is_active(dev_priv);
}

static void intel_fbc_hw_activate(struct drm_i915_private *dev_priv)
{
        struct intel_fbc *fbc = &dev_priv->fbc;

        fbc->active = true;

        if (INTEL_GEN(dev_priv) >= 7)
                gen7_fbc_activate(dev_priv);
        else if (INTEL_GEN(dev_priv) >= 5)
                ilk_fbc_activate(dev_priv);
        else if (IS_GM45(dev_priv))
                g4x_fbc_activate(dev_priv);
        else
                i8xx_fbc_activate(dev_priv);
}

static void intel_fbc_hw_deactivate(struct drm_i915_private *dev_priv)
{
        struct intel_fbc *fbc = &dev_priv->fbc;

        fbc->active = false;

        if (INTEL_GEN(dev_priv) >= 5)
                ilk_fbc_deactivate(dev_priv);
        else if (IS_GM45(dev_priv))
                g4x_fbc_deactivate(dev_priv);
        else
                i8xx_fbc_deactivate(dev_priv);
}

/**
 * intel_fbc_is_active - Is FBC active?
 * @dev_priv: i915 device instance
 *
 * This function is used to verify the current state of FBC.
 *
 * FIXME: This should be tracked in the plane config eventually
 * instead of queried at runtime for most callers.
 */
bool intel_fbc_is_active(struct drm_i915_private *dev_priv)
{
        return dev_priv->fbc.active;
}

static void intel_fbc_work_fn(struct work_struct *__work)
{
        struct drm_i915_private *dev_priv =
                container_of(__work, struct drm_i915_private, fbc.work.work);
        struct intel_fbc *fbc = &dev_priv->fbc;
        struct intel_fbc_work *work = &fbc->work;
        struct intel_crtc *crtc = fbc->crtc;
        struct drm_vblank_crtc *vblank = &dev_priv->drm.vblank[crtc->pipe];

        if (drm_crtc_vblank_get(&crtc->base)) {
                DRM_ERROR("vblank not available for FBC on pipe %c\n",
                          pipe_name(crtc->pipe));

                mutex_lock(&fbc->lock);
                work->scheduled = false;
                mutex_unlock(&fbc->lock);
                return;
        }

retry:
        /* Delay the actual enabling to let pageflipping cease and the
         * display to settle before starting the compression. Note that
         * this delay also serves a second purpose: it allows for a
         * vblank to pass after disabling the FBC before we attempt
         * to modify the control registers.
         *
         * WaFbcWaitForVBlankBeforeEnable:ilk,snb
         *
         * It is also worth mentioning that since work->scheduled_vblank can be
         * updated multiple times by the other threads, hitting the timeout is
         * not an error condition. We'll just end up hitting the "goto retry"
         * case below.
         */
        wait_event_timeout(vblank->queue,
                drm_crtc_vblank_count(&crtc->base) != work->scheduled_vblank,
                msecs_to_jiffies(50));

        mutex_lock(&fbc->lock);

        /* Were we cancelled? */
        if (!work->scheduled)
                goto out;

        /* Were we delayed again while this function was sleeping? */
        if (drm_crtc_vblank_count(&crtc->base) == work->scheduled_vblank) {
                mutex_unlock(&fbc->lock);
                goto retry;
        }

        intel_fbc_hw_activate(dev_priv);

        work->scheduled = false;

out:
        mutex_unlock(&fbc->lock);
        drm_crtc_vblank_put(&crtc->base);
}

static void intel_fbc_schedule_activation(struct intel_crtc *crtc)
{
        struct drm_i915_private *dev_priv = to_i915(crtc->base.dev);
        struct intel_fbc *fbc = &dev_priv->fbc;
        struct intel_fbc_work *work = &fbc->work;

        WARN_ON(!mutex_is_locked(&fbc->lock));

        if (drm_crtc_vblank_get(&crtc->base)) {
                DRM_ERROR("vblank not available for FBC on pipe %c\n",
                          pipe_name(crtc->pipe));
                return;
        }

        /* It is useless to call intel_fbc_cancel_work() or cancel_work() in
         * this function since we're not releasing fbc.lock, so it won't have an
         * opportunity to grab it to discover that it was cancelled. So we just
         * update the expected jiffy count. */
        work->scheduled = true;
        work->scheduled_vblank = drm_crtc_vblank_count(&crtc->base);
        drm_crtc_vblank_put(&crtc->base);

        schedule_work(&work->work);
}

static void intel_fbc_deactivate(struct drm_i915_private *dev_priv)
{
        struct intel_fbc *fbc = &dev_priv->fbc;

        WARN_ON(!mutex_is_locked(&fbc->lock));

        /* Calling cancel_work() here won't help due to the fact that the work
         * function grabs fbc->lock. Just set scheduled to false so the work
         * function can know it was cancelled. */
        fbc->work.scheduled = false;

        if (fbc->active)
                intel_fbc_hw_deactivate(dev_priv);
}

static bool multiple_pipes_ok(struct intel_crtc *crtc,
                              struct intel_plane_state *plane_state)
{
        struct drm_i915_private *dev_priv = to_i915(crtc->base.dev);
        struct intel_fbc *fbc = &dev_priv->fbc;
        enum pipe pipe = crtc->pipe;

        /* Don't even bother tracking anything we don't need. */
        if (!no_fbc_on_multiple_pipes(dev_priv))
                return true;

        if (plane_state->base.visible)
                fbc->visible_pipes_mask |= (1 << pipe);
        else
                fbc->visible_pipes_mask &= ~(1 << pipe);

        return (fbc->visible_pipes_mask & ~(1 << pipe)) != 0;
}

static int find_compression_threshold(struct drm_i915_private *dev_priv,
                                      struct drm_mm_node *node,
                                      int size,
                                      int fb_cpp)
{
        struct i915_ggtt *ggtt = &dev_priv->ggtt;
        int compression_threshold = 1;
        int ret;
        u64 end;

        /* The FBC hardware for BDW/SKL doesn't have access to the stolen
         * reserved range size, so it always assumes the maximum (8mb) is used.
         * If we enable FBC using a CFB on that memory range we'll get FIFO
         * underruns, even if that range is not reserved by the BIOS. */
        if (IS_BROADWELL(dev_priv) ||
            IS_SKYLAKE(dev_priv) || IS_KABYLAKE(dev_priv))
                end = ggtt->stolen_size - 8 * 1024 * 1024;
        else
                end = ggtt->stolen_usable_size;

        /* HACK: This code depends on what we will do in *_enable_fbc. If that
         * code changes, this code needs to change as well.
         *
         * The enable_fbc code will attempt to use one of our 2 compression
         * thresholds, therefore, in that case, we only have 1 resort.
         */

        /* Try to over-allocate to reduce reallocations and fragmentation. */
        ret = i915_gem_stolen_insert_node_in_range(dev_priv, node, size <<= 1,
                                                   4096, 0, end);
        if (ret == 0)
                return compression_threshold;

again:
        /* HW's ability to limit the CFB is 1:4 */
        if (compression_threshold > 4 ||
            (fb_cpp == 2 && compression_threshold == 2))
                return 0;

        ret = i915_gem_stolen_insert_node_in_range(dev_priv, node, size >>= 1,
                                                   4096, 0, end);
        if (ret && INTEL_GEN(dev_priv) <= 4) {
                return 0;
        } else if (ret) {
                compression_threshold <<= 1;
                goto again;
        } else {
                return compression_threshold;
        }
}

static int intel_fbc_alloc_cfb(struct intel_crtc *crtc)
{
        struct drm_i915_private *dev_priv = to_i915(crtc->base.dev);
        struct intel_fbc *fbc = &dev_priv->fbc;
        struct drm_mm_node *uninitialized_var(compressed_llb);
        int size, fb_cpp, ret;

        WARN_ON(drm_mm_node_allocated(&fbc->compressed_fb));

        size = intel_fbc_calculate_cfb_size(dev_priv, &fbc->state_cache);
        fb_cpp = drm_format_plane_cpp(fbc->state_cache.fb.pixel_format, 0);

        ret = find_compression_threshold(dev_priv, &fbc->compressed_fb,
                                         size, fb_cpp);
        if (!ret)
                goto err_llb;
        else if (ret > 1) {
                DRM_INFO("Reducing the compressed framebuffer size. This may lead to less power savings than a non-reduced-size. Try to increase stolen memory size if available in BIOS.\n");

        }

        fbc->threshold = ret;

        if (INTEL_GEN(dev_priv) >= 5)
                I915_WRITE(ILK_DPFC_CB_BASE, fbc->compressed_fb.start);
        else if (IS_GM45(dev_priv)) {
                I915_WRITE(DPFC_CB_BASE, fbc->compressed_fb.start);
        } else {
                compressed_llb = kzalloc(sizeof(*compressed_llb), GFP_KERNEL);
                if (!compressed_llb)
                        goto err_fb;

                ret = i915_gem_stolen_insert_node(dev_priv, compressed_llb,
                                                  4096, 4096);
                if (ret)
                        goto err_fb;

                fbc->compressed_llb = compressed_llb;

                I915_WRITE(FBC_CFB_BASE,
                           dev_priv->mm.stolen_base + fbc->compressed_fb.start);
                I915_WRITE(FBC_LL_BASE,
                           dev_priv->mm.stolen_base + compressed_llb->start);
        }

        DRM_DEBUG_KMS("reserved %llu bytes of contiguous stolen space for FBC, threshold: %d\n",
                      fbc->compressed_fb.size, fbc->threshold);

        return 0;

err_fb:
        kfree(compressed_llb);
        i915_gem_stolen_remove_node(dev_priv, &fbc->compressed_fb);
err_llb:
        pr_info_once("drm: not enough stolen space for compressed buffer (need %d more bytes), disabling. Hint: you may be able to increase stolen memory size in the BIOS to avoid this.\n", size);
        return -ENOSPC;
}

static void __intel_fbc_cleanup_cfb(struct drm_i915_private *dev_priv)
{
        struct intel_fbc *fbc = &dev_priv->fbc;

        if (drm_mm_node_allocated(&fbc->compressed_fb))
                i915_gem_stolen_remove_node(dev_priv, &fbc->compressed_fb);

        if (fbc->compressed_llb) {
                i915_gem_stolen_remove_node(dev_priv, fbc->compressed_llb);
                kfree(fbc->compressed_llb);
        }
}

void intel_fbc_cleanup_cfb(struct drm_i915_private *dev_priv)
{
        struct intel_fbc *fbc = &dev_priv->fbc;

        if (!fbc_supported(dev_priv))
                return;

        mutex_lock(&fbc->lock);
        __intel_fbc_cleanup_cfb(dev_priv);
        mutex_unlock(&fbc->lock);
}

static bool stride_is_valid(struct drm_i915_private *dev_priv,
                            unsigned int stride)
{
        /* These should have been caught earlier. */
        WARN_ON(stride < 512);
        WARN_ON((stride & (64 - 1)) != 0);

        /* Below are the additional FBC restrictions. */

        if (IS_GEN2(dev_priv) || IS_GEN3(dev_priv))
                return stride == 4096 || stride == 8192;

        if (IS_GEN4(dev_priv) && !IS_G4X(dev_priv) && stride < 2048)
                return false;

        if (stride > 16384)
                return false;

        return true;
}

static bool pixel_format_is_valid(struct drm_i915_private *dev_priv,
                                  uint32_t pixel_format)
{
        switch (pixel_format) {
        case DRM_FORMAT_XRGB8888:
        case DRM_FORMAT_XBGR8888:
                return true;
        case DRM_FORMAT_XRGB1555:
        case DRM_FORMAT_RGB565:
                /* 16bpp not supported on gen2 */
                if (IS_GEN2(dev_priv))
                        return false;
                /* WaFbcOnly1to1Ratio:ctg */
                if (IS_G4X(dev_priv))
                        return false;
                return true;
        default:
                return false;
        }
}

/*
 * For some reason, the hardware tracking starts looking at whatever we
 * programmed as the display plane base address register. It does not look at
 * the X and Y offset registers. That's why we look at the crtc->adjusted{x,y}
 * variables instead of just looking at the pipe/plane size.
 */
static bool intel_fbc_hw_tracking_covers_screen(struct intel_crtc *crtc)
{
        struct drm_i915_private *dev_priv = to_i915(crtc->base.dev);
        struct intel_fbc *fbc = &dev_priv->fbc;
        unsigned int effective_w, effective_h, max_w, max_h;

        if (INTEL_GEN(dev_priv) >= 8 || IS_HASWELL(dev_priv)) {
                max_w = 4096;
                max_h = 4096;
        } else if (IS_G4X(dev_priv) || INTEL_GEN(dev_priv) >= 5) {
                max_w = 4096;
                max_h = 2048;
        } else {
                max_w = 2048;
                max_h = 1536;
        }

        intel_fbc_get_plane_source_size(&fbc->state_cache, &effective_w,
                                        &effective_h);
        effective_w += crtc->adjusted_x;
        effective_h += crtc->adjusted_y;

        return effective_w <= max_w && effective_h <= max_h;
}

/* XXX replace me when we have VMA tracking for intel_plane_state */
static int get_fence_id(struct drm_framebuffer *fb)
{
        struct i915_vma *vma = i915_gem_object_to_ggtt(intel_fb_obj(fb), NULL);

        return vma && vma->fence ? vma->fence->id : I915_FENCE_REG_NONE;
}

static void intel_fbc_update_state_cache(struct intel_crtc *crtc,
                                         struct intel_crtc_state *crtc_state,
                                         struct intel_plane_state *plane_state)
{
        struct drm_i915_private *dev_priv = to_i915(crtc->base.dev);
        struct intel_fbc *fbc = &dev_priv->fbc;
        struct intel_fbc_state_cache *cache = &fbc->state_cache;
        struct drm_framebuffer *fb = plane_state->base.fb;
        struct drm_i915_gem_object *obj;

        cache->crtc.mode_flags = crtc_state->base.adjusted_mode.flags;
        if (IS_HASWELL(dev_priv) || IS_BROADWELL(dev_priv))
                cache->crtc.hsw_bdw_pixel_rate =
                        ilk_pipe_pixel_rate(crtc_state);

        cache->plane.rotation = plane_state->base.rotation;
        cache->plane.src_w = drm_rect_width(&plane_state->base.src) >> 16;
        cache->plane.src_h = drm_rect_height(&plane_state->base.src) >> 16;
        cache->plane.visible = plane_state->base.visible;

        if (!cache->plane.visible)
                return;

        obj = intel_fb_obj(fb);

        /* FIXME: We lack the proper locking here, so only run this on the
         * platforms that need. */
        if (IS_GEN(dev_priv, 5, 6))
                cache->fb.ilk_ggtt_offset = i915_gem_object_ggtt_offset(obj, NULL);
        cache->fb.pixel_format = fb->pixel_format;
        cache->fb.stride = fb->pitches[0];
        cache->fb.fence_reg = get_fence_id(fb);
        cache->fb.tiling_mode = i915_gem_object_get_tiling(obj);
}

static bool intel_fbc_can_activate(struct intel_crtc *crtc)
{
        struct drm_i915_private *dev_priv = to_i915(crtc->base.dev);
        struct intel_fbc *fbc = &dev_priv->fbc;
        struct intel_fbc_state_cache *cache = &fbc->state_cache;

        /* We don't need to use a state cache here since this information is
         * global for all CRTC.
         */
        if (fbc->underrun_detected) {
                fbc->no_fbc_reason = "underrun detected";
                return false;
        }

        if (!cache->plane.visible) {
                fbc->no_fbc_reason = "primary plane not visible";
                return false;
        }

        if ((cache->crtc.mode_flags & DRM_MODE_FLAG_INTERLACE) ||
            (cache->crtc.mode_flags & DRM_MODE_FLAG_DBLSCAN)) {
                fbc->no_fbc_reason = "incompatible mode";
                return false;
        }

        if (!intel_fbc_hw_tracking_covers_screen(crtc)) {
                fbc->no_fbc_reason = "mode too large for compression";
                return false;
        }

        /* The use of a CPU fence is mandatory in order to detect writes
         * by the CPU to the scanout and trigger updates to the FBC.
         *
         * Note that is possible for a tiled surface to be unmappable (and
         * so have no fence associated with it) due to aperture constaints
         * at the time of pinning.
         */
        if (cache->fb.tiling_mode != I915_TILING_X ||
            cache->fb.fence_reg == I915_FENCE_REG_NONE) {
                fbc->no_fbc_reason = "framebuffer not tiled or fenced";
                return false;
        }
        if (INTEL_GEN(dev_priv) <= 4 && !IS_G4X(dev_priv) &&
            cache->plane.rotation != DRM_ROTATE_0) {
                fbc->no_fbc_reason = "rotation unsupported";
                return false;
        }

        if (!stride_is_valid(dev_priv, cache->fb.stride)) {
                fbc->no_fbc_reason = "framebuffer stride not supported";
                return false;
        }

        if (!pixel_format_is_valid(dev_priv, cache->fb.pixel_format)) {
                fbc->no_fbc_reason = "pixel format is invalid";
                return false;
        }

        /* WaFbcExceedCdClockThreshold:hsw,bdw */
        if ((IS_HASWELL(dev_priv) || IS_BROADWELL(dev_priv)) &&
            cache->crtc.hsw_bdw_pixel_rate >= dev_priv->cdclk_freq * 95 / 100) {
                fbc->no_fbc_reason = "pixel rate is too big";
                return false;
        }

        /* It is possible for the required CFB size change without a
         * crtc->disable + crtc->enable since it is possible to change the
         * stride without triggering a full modeset. Since we try to
         * over-allocate the CFB, there's a chance we may keep FBC enabled even
         * if this happens, but if we exceed the current CFB size we'll have to
         * disable FBC. Notice that it would be possible to disable FBC, wait
         * for a frame, free the stolen node, then try to reenable FBC in case
         * we didn't get any invalidate/deactivate calls, but this would require
         * a lot of tracking just for a specific case. If we conclude it's an
         * important case, we can implement it later. */
        if (intel_fbc_calculate_cfb_size(dev_priv, &fbc->state_cache) >
            fbc->compressed_fb.size * fbc->threshold) {
                fbc->no_fbc_reason = "CFB requirements changed";
                return false;
        }

        return true;
}

static bool intel_fbc_can_enable(struct drm_i915_private *dev_priv)
{
        struct intel_fbc *fbc = &dev_priv->fbc;

        if (intel_vgpu_active(dev_priv)) {
                fbc->no_fbc_reason = "VGPU is active";
                return false;
        }

        if (!i915.enable_fbc) {
                fbc->no_fbc_reason = "disabled per module param or by default";
                return false;
        }

        if (fbc->underrun_detected) {
                fbc->no_fbc_reason = "underrun detected";
                return false;
        }

        return true;
}

static void intel_fbc_get_reg_params(struct intel_crtc *crtc,
                                     struct intel_fbc_reg_params *params)
{
        struct drm_i915_private *dev_priv = to_i915(crtc->base.dev);
        struct intel_fbc *fbc = &dev_priv->fbc;
        struct intel_fbc_state_cache *cache = &fbc->state_cache;

        /* Since all our fields are integer types, use memset here so the
         * comparison function can rely on memcmp because the padding will be
         * zero. */
        memset(params, 0, sizeof(*params));

        params->crtc.pipe = crtc->pipe;
        params->crtc.plane = crtc->plane;
        params->crtc.fence_y_offset = get_crtc_fence_y_offset(crtc);

        params->fb.pixel_format = cache->fb.pixel_format;
        params->fb.stride = cache->fb.stride;
        params->fb.fence_reg = cache->fb.fence_reg;

        params->cfb_size = intel_fbc_calculate_cfb_size(dev_priv, cache);

        params->fb.ggtt_offset = cache->fb.ilk_ggtt_offset;
}

static bool intel_fbc_reg_params_equal(struct intel_fbc_reg_params *params1,
                                       struct intel_fbc_reg_params *params2)
{
        /* We can use this since intel_fbc_get_reg_params() does a memset. */
        return memcmp(params1, params2, sizeof(*params1)) == 0;
}

void intel_fbc_pre_update(struct intel_crtc *crtc,
                          struct intel_crtc_state *crtc_state,
                          struct intel_plane_state *plane_state)
{
        struct drm_i915_private *dev_priv = to_i915(crtc->base.dev);
        struct intel_fbc *fbc = &dev_priv->fbc;

        if (!fbc_supported(dev_priv))
                return;

        mutex_lock(&fbc->lock);

        if (!multiple_pipes_ok(crtc, plane_state)) {
                fbc->no_fbc_reason = "more than one pipe active";
                goto deactivate;
        }

        if (!fbc->enabled || fbc->crtc != crtc)
                goto unlock;

        intel_fbc_update_state_cache(crtc, crtc_state, plane_state);

deactivate:
        intel_fbc_deactivate(dev_priv);
unlock:
        mutex_unlock(&fbc->lock);
}

static void __intel_fbc_post_update(struct intel_crtc *crtc)
{
        struct drm_i915_private *dev_priv = to_i915(crtc->base.dev);
        struct intel_fbc *fbc = &dev_priv->fbc;
        struct intel_fbc_reg_params old_params;

        WARN_ON(!mutex_is_locked(&fbc->lock));

        if (!fbc->enabled || fbc->crtc != crtc)
                return;

        if (!intel_fbc_can_activate(crtc)) {
                WARN_ON(fbc->active);
                return;
        }

        old_params = fbc->params;
        intel_fbc_get_reg_params(crtc, &fbc->params);

        /* If the scanout has not changed, don't modify the FBC settings.
         * Note that we make the fundamental assumption that the fb->obj
         * cannot be unpinned (and have its GTT offset and fence revoked)
         * without first being decoupled from the scanout and FBC disabled.
         */
        if (fbc->active &&
            intel_fbc_reg_params_equal(&old_params, &fbc->params))
                return;

        intel_fbc_deactivate(dev_priv);
        intel_fbc_schedule_activation(crtc);
        fbc->no_fbc_reason = "FBC enabled (active or scheduled)";
}

void intel_fbc_post_update(struct intel_crtc *crtc)
{
        struct drm_i915_private *dev_priv = to_i915(crtc->base.dev);
        struct intel_fbc *fbc = &dev_priv->fbc;

        if (!fbc_supported(dev_priv))
                return;

        mutex_lock(&fbc->lock);
        __intel_fbc_post_update(crtc);
        mutex_unlock(&fbc->lock);
}

static unsigned int intel_fbc_get_frontbuffer_bit(struct intel_fbc *fbc)
{
        if (fbc->enabled)
                return to_intel_plane(fbc->crtc->base.primary)->frontbuffer_bit;
        else
                return fbc->possible_framebuffer_bits;
}

void intel_fbc_invalidate(struct drm_i915_private *dev_priv,
                          unsigned int frontbuffer_bits,
                          enum fb_op_origin origin)
{
        struct intel_fbc *fbc = &dev_priv->fbc;

        if (!fbc_supported(dev_priv))
                return;

        if (origin == ORIGIN_GTT || origin == ORIGIN_FLIP)
                return;

        mutex_lock(&fbc->lock);

        fbc->busy_bits |= intel_fbc_get_frontbuffer_bit(fbc) & frontbuffer_bits;

        if (fbc->enabled && fbc->busy_bits)
                intel_fbc_deactivate(dev_priv);

        mutex_unlock(&fbc->lock);
}

void intel_fbc_flush(struct drm_i915_private *dev_priv,
                     unsigned int frontbuffer_bits, enum fb_op_origin origin)
{
        struct intel_fbc *fbc = &dev_priv->fbc;

        if (!fbc_supported(dev_priv))
                return;

        mutex_lock(&fbc->lock);

        fbc->busy_bits &= ~frontbuffer_bits;

        if (origin == ORIGIN_GTT || origin == ORIGIN_FLIP)
                goto out;

        if (!fbc->busy_bits && fbc->enabled &&
            (frontbuffer_bits & intel_fbc_get_frontbuffer_bit(fbc))) {
                if (fbc->active)
                        intel_fbc_recompress(dev_priv);
                else
                        __intel_fbc_post_update(fbc->crtc);
        }

out:
        mutex_unlock(&fbc->lock);
}

/**
 * intel_fbc_choose_crtc - select a CRTC to enable FBC on
 * @dev_priv: i915 device instance
 * @state: the atomic state structure
 *
 * This function looks at the proposed state for CRTCs and planes, then chooses
 * which pipe is going to have FBC by setting intel_crtc_state->enable_fbc to
 * true.
 *
 * Later, intel_fbc_enable is going to look for state->enable_fbc and then maybe
 * enable FBC for the chosen CRTC. If it does, it will set dev_priv->fbc.crtc.
 */
void intel_fbc_choose_crtc(struct drm_i915_private *dev_priv,
                           struct drm_atomic_state *state)
{
        struct intel_fbc *fbc = &dev_priv->fbc;
        struct drm_plane *plane;
        struct drm_plane_state *plane_state;
        bool crtc_chosen = false;
        int i;

        mutex_lock(&fbc->lock);

        /* Does this atomic commit involve the CRTC currently tied to FBC? */
        if (fbc->crtc &&
            !drm_atomic_get_existing_crtc_state(state, &fbc->crtc->base))
                goto out;

        if (!intel_fbc_can_enable(dev_priv))
                goto out;

        /* Simply choose the first CRTC that is compatible and has a visible
         * plane. We could go for fancier schemes such as checking the plane
         * size, but this would just affect the few platforms that don't tie FBC
         * to pipe or plane A. */
        for_each_plane_in_state(state, plane, plane_state, i) {
                struct intel_plane_state *intel_plane_state =
                        to_intel_plane_state(plane_state);
                struct intel_crtc_state *intel_crtc_state;
                struct intel_crtc *crtc = to_intel_crtc(plane_state->crtc);

                if (!intel_plane_state->base.visible)
                        continue;

                if (fbc_on_pipe_a_only(dev_priv) && crtc->pipe != PIPE_A)
                        continue;

                if (fbc_on_plane_a_only(dev_priv) && crtc->plane != PLANE_A)
                        continue;

                intel_crtc_state = to_intel_crtc_state(
                        drm_atomic_get_existing_crtc_state(state, &crtc->base));

                intel_crtc_state->enable_fbc = true;
                crtc_chosen = true;
                break;
        }

        if (!crtc_chosen)
                fbc->no_fbc_reason = "no suitable CRTC for FBC";

out:
        mutex_unlock(&fbc->lock);
}

/**
 * intel_fbc_enable: tries to enable FBC on the CRTC
 * @crtc: the CRTC
 * @crtc_state: corresponding &drm_crtc_state for @crtc
 * @plane_state: corresponding &drm_plane_state for the primary plane of @crtc
 *
 * This function checks if the given CRTC was chosen for FBC, then enables it if
 * possible. Notice that it doesn't activate FBC. It is valid to call
 * intel_fbc_enable multiple times for the same pipe without an
 * intel_fbc_disable in the middle, as long as it is deactivated.
 */
void intel_fbc_enable(struct intel_crtc *crtc,
                      struct intel_crtc_state *crtc_state,
                      struct intel_plane_state *plane_state)
{
        struct drm_i915_private *dev_priv = to_i915(crtc->base.dev);
        struct intel_fbc *fbc = &dev_priv->fbc;

        if (!fbc_supported(dev_priv))
                return;

        mutex_lock(&fbc->lock);

        if (fbc->enabled) {
                WARN_ON(fbc->crtc == NULL);
                if (fbc->crtc == crtc) {
                        WARN_ON(!crtc_state->enable_fbc);
                        WARN_ON(fbc->active);
                }
                goto out;
        }

        if (!crtc_state->enable_fbc)
                goto out;

        WARN_ON(fbc->active);
        WARN_ON(fbc->crtc != NULL);

        intel_fbc_update_state_cache(crtc, crtc_state, plane_state);
        if (intel_fbc_alloc_cfb(crtc)) {
                fbc->no_fbc_reason = "not enough stolen memory";
                goto out;
        }

        DRM_DEBUG_KMS("Enabling FBC on pipe %c\n", pipe_name(crtc->pipe));
        fbc->no_fbc_reason = "FBC enabled but not active yet\n";

        fbc->enabled = true;
        fbc->crtc = crtc;
out:
        mutex_unlock(&fbc->lock);
}

/**
 * __intel_fbc_disable - disable FBC
 * @dev_priv: i915 device instance
 *
 * This is the low level function that actually disables FBC. Callers should
 * grab the FBC lock.
 */
static void __intel_fbc_disable(struct drm_i915_private *dev_priv)
{
        struct intel_fbc *fbc = &dev_priv->fbc;
        struct intel_crtc *crtc = fbc->crtc;

        WARN_ON(!mutex_is_locked(&fbc->lock));
        WARN_ON(!fbc->enabled);
        WARN_ON(fbc->active);
        WARN_ON(crtc->active);

        DRM_DEBUG_KMS("Disabling FBC on pipe %c\n", pipe_name(crtc->pipe));

        __intel_fbc_cleanup_cfb(dev_priv);

        fbc->enabled = false;
        fbc->crtc = NULL;
}

/**
 * intel_fbc_disable - disable FBC if it's associated with crtc
 * @crtc: the CRTC
 *
 * This function disables FBC if it's associated with the provided CRTC.
 */
void intel_fbc_disable(struct intel_crtc *crtc)
{
        struct drm_i915_private *dev_priv = to_i915(crtc->base.dev);
        struct intel_fbc *fbc = &dev_priv->fbc;

        if (!fbc_supported(dev_priv))
                return;

        mutex_lock(&fbc->lock);
        if (fbc->crtc == crtc)
                __intel_fbc_disable(dev_priv);
        mutex_unlock(&fbc->lock);

        cancel_work_sync(&fbc->work.work);
}

/**
 * intel_fbc_global_disable - globally disable FBC
 * @dev_priv: i915 device instance
 *
 * This function disables FBC regardless of which CRTC is associated with it.
 */
void intel_fbc_global_disable(struct drm_i915_private *dev_priv)
{
        struct intel_fbc *fbc = &dev_priv->fbc;

        if (!fbc_supported(dev_priv))
                return;

        mutex_lock(&fbc->lock);
        if (fbc->enabled)
                __intel_fbc_disable(dev_priv);
        mutex_unlock(&fbc->lock);

        cancel_work_sync(&fbc->work.work);
}

static void intel_fbc_underrun_work_fn(struct work_struct *work)
{
        struct drm_i915_private *dev_priv =
                container_of(work, struct drm_i915_private, fbc.underrun_work);
        struct intel_fbc *fbc = &dev_priv->fbc;

        mutex_lock(&fbc->lock);

        /* Maybe we were scheduled twice. */
        if (fbc->underrun_detected)
                goto out;

        DRM_DEBUG_KMS("Disabling FBC due to FIFO underrun.\n");
        fbc->underrun_detected = true;

        intel_fbc_deactivate(dev_priv);
out:
        mutex_unlock(&fbc->lock);
}

/**
 * intel_fbc_handle_fifo_underrun_irq - disable FBC when we get a FIFO underrun
 * @dev_priv: i915 device instance
 *
 * Without FBC, most underruns are harmless and don't really cause too many
 * problems, except for an annoying message on dmesg. With FBC, underruns can
 * become black screens or even worse, especially when paired with bad
 * watermarks. So in order for us to be on the safe side, completely disable FBC
 * in case we ever detect a FIFO underrun on any pipe. An underrun on any pipe
 * already suggests that watermarks may be bad, so try to be as safe as
 * possible.
 *
 * This function is called from the IRQ handler.
 */
void intel_fbc_handle_fifo_underrun_irq(struct drm_i915_private *dev_priv)
{
        struct intel_fbc *fbc = &dev_priv->fbc;

        if (!fbc_supported(dev_priv))
                return;

        /* There's no guarantee that underrun_detected won't be set to true
         * right after this check and before the work is scheduled, but that's
         * not a problem since we'll check it again under the work function
         * while FBC is locked. This check here is just to prevent us from
         * unnecessarily scheduling the work, and it relies on the fact that we
         * never switch underrun_detect back to false after it's true. */
        if (READ_ONCE(fbc->underrun_detected))
                return;

        schedule_work(&fbc->underrun_work);
}

/**
 * intel_fbc_init_pipe_state - initialize FBC's CRTC visibility tracking
 * @dev_priv: i915 device instance
 *
 * The FBC code needs to track CRTC visibility since the older platforms can't
 * have FBC enabled while multiple pipes are used. This function does the
 * initial setup at driver load to make sure FBC is matching the real hardware.
 */
void intel_fbc_init_pipe_state(struct drm_i915_private *dev_priv)
{
        struct intel_crtc *crtc;

        /* Don't even bother tracking anything if we don't need. */
        if (!no_fbc_on_multiple_pipes(dev_priv))
                return;

        for_each_intel_crtc(&dev_priv->drm, crtc)
                if (intel_crtc_active(crtc) &&
                    to_intel_plane_state(crtc->base.primary->state)->base.visible)
                        dev_priv->fbc.visible_pipes_mask |= (1 << crtc->pipe);
}

/*
 * The DDX driver changes its behavior depending on the value it reads from
 * i915.enable_fbc, so sanitize it by translating the default value into either
 * 0 or 1 in order to allow it to know what's going on.
 *
 * Notice that this is done at driver initialization and we still allow user
 * space to change the value during runtime without sanitizing it again. IGT
 * relies on being able to change i915.enable_fbc at runtime.
 */
static int intel_sanitize_fbc_option(struct drm_i915_private *dev_priv)
{
        if (i915.enable_fbc >= 0)
                return !!i915.enable_fbc;

        if (!HAS_FBC(dev_priv))
                return 0;

        if (IS_BROADWELL(dev_priv))
                return 1;

        return 0;
}

static bool need_fbc_vtd_wa(struct drm_i915_private *dev_priv)
{
#ifdef CONFIG_INTEL_IOMMU
        /* WaFbcTurnOffFbcWhenHyperVisorIsUsed:skl,bxt */
        if (intel_iommu_gfx_mapped &&
            (IS_SKYLAKE(dev_priv) || IS_BROXTON(dev_priv))) {
                DRM_INFO("Disabling framebuffer compression (FBC) to prevent screen flicker with VT-d enabled\n");
                return true;
        }
#endif

        return false;
}

/**
 * intel_fbc_init - Initialize FBC
 * @dev_priv: the i915 device
 *
 * This function might be called during PM init process.
 */
void intel_fbc_init(struct drm_i915_private *dev_priv)
{
        struct intel_fbc *fbc = &dev_priv->fbc;
        enum pipe pipe;

        INIT_WORK(&fbc->work.work, intel_fbc_work_fn);
        INIT_WORK(&fbc->underrun_work, intel_fbc_underrun_work_fn);
        mutex_init(&fbc->lock);
        fbc->enabled = false;
        fbc->active = false;
        fbc->work.scheduled = false;

        if (need_fbc_vtd_wa(dev_priv))
                mkwrite_device_info(dev_priv)->has_fbc = false;

        i915.enable_fbc = intel_sanitize_fbc_option(dev_priv);
        DRM_DEBUG_KMS("Sanitized enable_fbc value: %d\n", i915.enable_fbc);

        if (!HAS_FBC(dev_priv)) {
                fbc->no_fbc_reason = "unsupported by this chipset";
                return;
        }

        for_each_pipe(dev_priv, pipe) {
                fbc->possible_framebuffer_bits |=
                                INTEL_FRONTBUFFER_PRIMARY(pipe);

                if (fbc_on_pipe_a_only(dev_priv))
                        break;
        }

        /* This value was pulled out of someone's hat */
        if (INTEL_GEN(dev_priv) <= 4 && !IS_GM45(dev_priv))
                I915_WRITE(FBC_CONTROL, 500 << FBC_CTL_INTERVAL_SHIFT);

        /* We still don't have any sort of hardware state readout for FBC, so
         * deactivate it in case the BIOS activated it to make sure software
         * matches the hardware state. */
        if (intel_fbc_hw_is_active(dev_priv))
                intel_fbc_hw_deactivate(dev_priv);
}