From baf69ca8a51c8a5ef6ef869f684764459a9b6fa2 Mon Sep 17 00:00:00 2001 From: =?utf8?q?Ville=20Syrj=C3=A4l=C3=A4?= Date: Fri, 21 Apr 2017 21:14:27 +0300 Subject: [PATCH] drm/i915: Refactor wm calculations MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit All platforms until SKL compute their watermarks essentially using the same method1/small buffer and method2/large buffer formulas. Most just open code it in slightly different ways. Let's pull it all into common helpers. This makes it a little easier to spot the actual differences. While at it try to add some docs explainign what the formulas are trying to do. Signed-off-by: Ville Syrjälä Link: http://patchwork.freedesktop.org/patch/msgid/20170421181432.15216-11-ville.syrjala@linux.intel.com Reviewed-by: Maarten Lankhorst --- drivers/gpu/drm/i915/intel_pm.c | 221 +++++++++++++++++++++----------- 1 file changed, 149 insertions(+), 72 deletions(-) diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c index c43fcd5d29b2..c07f3b2b0972 100644 --- a/drivers/gpu/drm/i915/intel_pm.c +++ b/drivers/gpu/drm/i915/intel_pm.c @@ -625,9 +625,105 @@ static const struct intel_watermark_params i845_wm_info = { .cacheline_size = I830_FIFO_LINE_SIZE, }; +/** + * intel_wm_method1 - Method 1 / "small buffer" watermark formula + * @pixel_rate: Pipe pixel rate in kHz + * @cpp: Plane bytes per pixel + * @latency: Memory wakeup latency in 0.1us units + * + * Compute the watermark using the method 1 or "small buffer" + * formula. The caller may additonally add extra cachelines + * to account for TLB misses and clock crossings. + * + * This method is concerned with the short term drain rate + * of the FIFO, ie. it does not account for blanking periods + * which would effectively reduce the average drain rate across + * a longer period. The name "small" refers to the fact the + * FIFO is relatively small compared to the amount of data + * fetched. + * + * The FIFO level vs. time graph might look something like: + * + * |\ |\ + * | \ | \ + * __---__---__ (- plane active, _ blanking) + * -> time + * + * or perhaps like this: + * + * |\|\ |\|\ + * __----__----__ (- plane active, _ blanking) + * -> time + * + * Returns: + * The watermark in bytes + */ +static unsigned int intel_wm_method1(unsigned int pixel_rate, + unsigned int cpp, + unsigned int latency) +{ + uint64_t ret; + + ret = (uint64_t) pixel_rate * cpp * latency; + ret = DIV_ROUND_UP_ULL(ret, 10000); + + return ret; +} + +/** + * intel_wm_method2 - Method 2 / "large buffer" watermark formula + * @pixel_rate: Pipe pixel rate in kHz + * @htotal: Pipe horizontal total + * @width: Plane width in pixels + * @cpp: Plane bytes per pixel + * @latency: Memory wakeup latency in 0.1us units + * + * Compute the watermark using the method 2 or "large buffer" + * formula. The caller may additonally add extra cachelines + * to account for TLB misses and clock crossings. + * + * This method is concerned with the long term drain rate + * of the FIFO, ie. it does account for blanking periods + * which effectively reduce the average drain rate across + * a longer period. The name "large" refers to the fact the + * FIFO is relatively large compared to the amount of data + * fetched. + * + * The FIFO level vs. time graph might look something like: + * + * |\___ |\___ + * | \___ | \___ + * | \ | \ + * __ --__--__--__--__--__--__ (- plane active, _ blanking) + * -> time + * + * Returns: + * The watermark in bytes + */ +static unsigned int intel_wm_method2(unsigned int pixel_rate, + unsigned int htotal, + unsigned int width, + unsigned int cpp, + unsigned int latency) +{ + unsigned int ret; + + /* + * FIXME remove once all users are computing + * watermarks in the correct place. + */ + if (WARN_ON_ONCE(htotal == 0)) + htotal = 1; + + ret = (latency * pixel_rate) / (htotal * 10000); + ret = (ret + 1) * width * cpp; + + return ret; +} + /** * intel_calculate_wm - calculate watermark level - * @clock_in_khz: pixel clock + * @pixel_rate: pixel clock * @wm: chip FIFO params * @cpp: bytes per pixel * @latency_ns: memory latency for the platform @@ -643,12 +739,12 @@ static const struct intel_watermark_params i845_wm_info = { * past the watermark point. If the FIFO drains completely, a FIFO underrun * will occur, and a display engine hang could result. */ -static unsigned long intel_calculate_wm(unsigned long clock_in_khz, - const struct intel_watermark_params *wm, - int fifo_size, int cpp, - unsigned long latency_ns) +static unsigned int intel_calculate_wm(int pixel_rate, + const struct intel_watermark_params *wm, + int fifo_size, int cpp, + unsigned int latency_ns) { - long entries_required, wm_size; + int entries, wm_size; /* * Note: we need to make sure we don't overflow for various clock & @@ -656,18 +752,17 @@ static unsigned long intel_calculate_wm(unsigned long clock_in_khz, * clocks go from a few thousand to several hundred thousand. * latency is usually a few thousand */ - entries_required = ((clock_in_khz / 1000) * cpp * latency_ns) / - 1000; - entries_required = DIV_ROUND_UP(entries_required, wm->cacheline_size); - - DRM_DEBUG_KMS("FIFO entries required for mode: %ld\n", entries_required); + entries = intel_wm_method1(pixel_rate, cpp, + latency_ns / 100); + entries = DIV_ROUND_UP(entries, wm->cacheline_size) + + wm->guard_size; + DRM_DEBUG_KMS("FIFO entries required for mode: %d\n", entries); - wm_size = fifo_size - (entries_required + wm->guard_size); - - DRM_DEBUG_KMS("FIFO watermark level: %ld\n", wm_size); + wm_size = fifo_size - entries; + DRM_DEBUG_KMS("FIFO watermark level: %d\n", wm_size); /* Don't promote wm_size to unsigned... */ - if (wm_size > (long)wm->max_wm) + if (wm_size > wm->max_wm) wm_size = wm->max_wm; if (wm_size <= 0) wm_size = wm->default_wm; @@ -734,7 +829,7 @@ static void pineview_update_wm(struct intel_crtc *unused_crtc) struct intel_crtc *crtc; const struct cxsr_latency *latency; u32 reg; - unsigned long wm; + unsigned int wm; latency = intel_get_cxsr_latency(IS_PINEVIEW_G(dev_priv), dev_priv->is_ddr3, @@ -829,7 +924,6 @@ static bool g4x_compute_wm0(struct drm_i915_private *dev_priv, const struct drm_display_mode *adjusted_mode; const struct drm_framebuffer *fb; int htotal, plane_width, cursor_width, clock, cpp; - int line_time_us, line_count; int entries; crtc = intel_get_crtc_for_plane(dev_priv, plane); @@ -848,7 +942,7 @@ static bool g4x_compute_wm0(struct drm_i915_private *dev_priv, cpp = fb->format->cpp[0]; /* Use the small buffer method to calculate plane watermark */ - entries = ((clock * cpp / 1000) * display_latency_ns) / 1000; + entries = intel_wm_method1(clock, cpp, display_latency_ns / 100); entries += g4x_tlb_miss_wa(display->fifo_size, plane_width, cpp); entries = DIV_ROUND_UP(entries, display->cacheline_size); *plane_wm = entries + display->guard_size; @@ -856,9 +950,8 @@ static bool g4x_compute_wm0(struct drm_i915_private *dev_priv, *plane_wm = display->max_wm; /* Use the large buffer method to calculate cursor watermark */ - line_time_us = max(htotal * 1000 / clock, 1); - line_count = (cursor_latency_ns / line_time_us + 1000) / 1000; - entries = line_count * cursor_width * 4; + entries = intel_wm_method2(clock, htotal, cursor_width, 4, + cursor_latency_ns / 100); entries += g4x_tlb_miss_wa(cursor->fifo_size, cursor_width, 4); entries = DIV_ROUND_UP(entries, cursor->cacheline_size); *cursor_wm = entries + cursor->guard_size; @@ -914,8 +1007,6 @@ static bool g4x_compute_srwm(struct drm_i915_private *dev_priv, const struct drm_display_mode *adjusted_mode; const struct drm_framebuffer *fb; int hdisplay, htotal, cpp, clock; - unsigned long line_time_us; - int line_count, line_size; int small, large; int entries; @@ -932,19 +1023,17 @@ static bool g4x_compute_srwm(struct drm_i915_private *dev_priv, hdisplay = crtc->config->pipe_src_w; cpp = fb->format->cpp[0]; - line_time_us = max(htotal * 1000 / clock, 1); - line_count = (latency_ns / line_time_us + 1000) / 1000; - line_size = hdisplay * cpp; - /* Use the minimum of the small and large buffer method for primary */ - small = ((clock * cpp / 1000) * latency_ns) / 1000; - large = line_count * line_size; - + small = intel_wm_method1(clock, cpp, latency_ns / 100); + large = intel_wm_method2(clock, htotal, hdisplay, cpp, + latency_ns / 100); entries = DIV_ROUND_UP(min(small, large), display->cacheline_size); *display_wm = entries + display->guard_size; /* calculate the self-refresh watermark for display cursor */ - entries = line_count * 4 * crtc->base.cursor->state->crtc_w; + entries = intel_wm_method2(clock, htotal, + crtc->base.cursor->state->crtc_w, 4, + latency_ns / 100); entries = DIV_ROUND_UP(entries, cursor->cacheline_size); *cursor_wm = entries + cursor->guard_size; @@ -1036,15 +1125,15 @@ static void vlv_write_wm_values(struct drm_i915_private *dev_priv, /* latency must be in 0.1us units. */ static unsigned int vlv_wm_method2(unsigned int pixel_rate, - unsigned int pipe_htotal, - unsigned int horiz_pixels, + unsigned int htotal, + unsigned int width, unsigned int cpp, unsigned int latency) { unsigned int ret; - ret = (latency * pixel_rate) / (pipe_htotal * 10000); - ret = (ret + 1) * horiz_pixels * cpp; + ret = intel_wm_method2(pixel_rate, htotal, + width, cpp, latency); ret = DIV_ROUND_UP(ret, 64); return ret; @@ -1085,8 +1174,6 @@ static uint16_t vlv_compute_wm_level(const struct intel_crtc_state *crtc_state, clock = adjusted_mode->crtc_clock; htotal = adjusted_mode->crtc_htotal; width = crtc_state->pipe_src_w; - if (WARN_ON(htotal == 0)) - htotal = 1; if (plane->id == PLANE_CURSOR) { /* @@ -1733,14 +1820,10 @@ static void i965_update_wm(struct intel_crtc *unused_crtc) int htotal = adjusted_mode->crtc_htotal; int hdisplay = crtc->config->pipe_src_w; int cpp = fb->format->cpp[0]; - unsigned long line_time_us; int entries; - line_time_us = max(htotal * 1000 / clock, 1); - - /* Use ns/us then divide to preserve precision */ - entries = (((sr_latency_ns / line_time_us) + 1000) / 1000) * - cpp * hdisplay; + entries = intel_wm_method2(clock, htotal, + hdisplay, cpp, sr_latency_ns / 100); entries = DIV_ROUND_UP(entries, I915_FIFO_LINE_SIZE); srwm = I965_FIFO_SIZE - entries; if (srwm < 0) @@ -1749,13 +1832,14 @@ static void i965_update_wm(struct intel_crtc *unused_crtc) DRM_DEBUG_KMS("self-refresh entries: %d, wm: %d\n", entries, srwm); - entries = (((sr_latency_ns / line_time_us) + 1000) / 1000) * - 4 * crtc->base.cursor->state->crtc_w; + entries = intel_wm_method2(clock, htotal, + crtc->base.cursor->state->crtc_w, 4, + sr_latency_ns / 100); entries = DIV_ROUND_UP(entries, - i965_cursor_wm_info.cacheline_size); - cursor_sr = i965_cursor_wm_info.fifo_size - - (entries + i965_cursor_wm_info.guard_size); + i965_cursor_wm_info.cacheline_size) + + i965_cursor_wm_info.guard_size; + cursor_sr = i965_cursor_wm_info.fifo_size - entries; if (cursor_sr > i965_cursor_wm_info.max_wm) cursor_sr = i965_cursor_wm_info.max_wm; @@ -1892,7 +1976,6 @@ static void i9xx_update_wm(struct intel_crtc *unused_crtc) int htotal = adjusted_mode->crtc_htotal; int hdisplay = enabled->config->pipe_src_w; int cpp; - unsigned long line_time_us; int entries; if (IS_I915GM(dev_priv) || IS_I945GM(dev_priv)) @@ -1900,11 +1983,8 @@ static void i9xx_update_wm(struct intel_crtc *unused_crtc) else cpp = fb->format->cpp[0]; - line_time_us = max(htotal * 1000 / clock, 1); - - /* Use ns/us then divide to preserve precision */ - entries = (((sr_latency_ns / line_time_us) + 1000) / 1000) * - cpp * hdisplay; + entries = intel_wm_method2(clock, htotal, hdisplay, cpp, + sr_latency_ns / 100); entries = DIV_ROUND_UP(entries, wm_info->cacheline_size); DRM_DEBUG_KMS("self-refresh entries: %d\n", entries); srwm = wm_info->fifo_size - entries; @@ -1961,34 +2041,31 @@ static void i845_update_wm(struct intel_crtc *unused_crtc) } /* latency must be in 0.1us units. */ -static uint32_t ilk_wm_method1(uint32_t pixel_rate, uint8_t cpp, uint32_t latency) +static unsigned int ilk_wm_method1(unsigned int pixel_rate, + unsigned int cpp, + unsigned int latency) { - uint64_t ret; - - if (WARN(latency == 0, "Latency value missing\n")) - return UINT_MAX; + unsigned int ret; - ret = (uint64_t) pixel_rate * cpp * latency; - ret = DIV_ROUND_UP_ULL(ret, 64 * 10000) + 2; + ret = intel_wm_method1(pixel_rate, cpp, latency); + ret = DIV_ROUND_UP(ret, 64) + 2; return ret; } /* latency must be in 0.1us units. */ -static uint32_t ilk_wm_method2(uint32_t pixel_rate, uint32_t pipe_htotal, - uint32_t horiz_pixels, uint8_t cpp, - uint32_t latency) +static unsigned int ilk_wm_method2(unsigned int pixel_rate, + unsigned int htotal, + unsigned int width, + unsigned int cpp, + unsigned int latency) { - uint32_t ret; - - if (WARN(latency == 0, "Latency value missing\n")) - return UINT_MAX; - if (WARN_ON(!pipe_htotal)) - return UINT_MAX; + unsigned int ret; - ret = (latency * pixel_rate) / (pipe_htotal * 10000); - ret = (ret + 1) * horiz_pixels * cpp; + ret = intel_wm_method2(pixel_rate, htotal, + width, cpp, latency); ret = DIV_ROUND_UP(ret, 64) + 2; + return ret; } -- 2.20.1