drm/radeon/kms: adjust evergreen display watermark setup

This patch fixes two issues:
- A disabled crtc does not use any lb, so return 0 for
lb size.  This makes the display priority calculation
more exact.
- Only use 1/2 and whole lb partitions. Using smaller
partitions can cause underflow to one of the displays
if you have multiple large displays on the same lb.

Fixes:
https://bugs.freedesktop.org/show_bug.cgi?id=34534

Signed-off-by: Alex Deucher <alexdeucher@gmail.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

diff --git a/drivers/gpu/drm/radeon/evergreen.c b/drivers/gpu/drm/radeon/evergreen.c
index 3453910ee0f383b48049b8f8c5405f11114f9256..43fd016744890e14c41408e6ccacf5c749208bd0 100644 (file)
--- a/drivers/gpu/drm/radeon/evergreen.c
+++ b/drivers/gpu/drm/radeon/evergreen.c
@@ -353,7 +353,7 @@ static u32 evergreen_line_buffer_adjust(struct radeon_device *rdev,
                                        struct drm_display_mode *mode,
                                        struct drm_display_mode *other_mode)
 {
-       u32 tmp = 0;
+       u32 tmp;
        /*
         * Line Buffer Setup
         * There are 3 line buffers, each one shared by 2 display controllers.
@@ -363,64 +363,63 @@ static u32 evergreen_line_buffer_adjust(struct radeon_device *rdev,
         * first display controller
         *  0 - first half of lb (3840 * 2)
         *  1 - first 3/4 of lb (5760 * 2)
-        *  2 - whole lb (7680 * 2)
+        *  2 - whole lb (7680 * 2), other crtc must be disabled
         *  3 - first 1/4 of lb (1920 * 2)
         * second display controller
         *  4 - second half of lb (3840 * 2)
         *  5 - second 3/4 of lb (5760 * 2)
-        *  6 - whole lb (7680 * 2)
+        *  6 - whole lb (7680 * 2), other crtc must be disabled
         *  7 - last 1/4 of lb (1920 * 2)
         */
-       if (mode && other_mode) {
-               if (mode->hdisplay > other_mode->hdisplay) {
-                       if (mode->hdisplay > 2560)
-                               tmp = 1; /* 3/4 */
-                       else
-                               tmp = 0; /* 1/2 */
-               } else if (other_mode->hdisplay > mode->hdisplay) {
-                       if (other_mode->hdisplay > 2560)
-                               tmp = 3; /* 1/4 */
-                       else
-                               tmp = 0; /* 1/2 */
-               } else
+       /* this can get tricky if we have two large displays on a paired group
+        * of crtcs.  Ideally for multiple large displays we'd assign them to
+        * non-linked crtcs for maximum line buffer allocation.
+        */
+       if (radeon_crtc->base.enabled && mode) {
+               if (other_mode)
                        tmp = 0; /* 1/2 */
-       } else if (mode)
-               tmp = 2; /* whole */
-       else if (other_mode)
-               tmp = 3; /* 1/4 */
+               else
+                       tmp = 2; /* whole */
+       } else
+               tmp = 0;
 
        /* second controller of the pair uses second half of the lb */
        if (radeon_crtc->crtc_id % 2)
                tmp += 4;
        WREG32(DC_LB_MEMORY_SPLIT + radeon_crtc->crtc_offset, tmp);
 
-       switch (tmp) {
-       case 0:
-       case 4:
-       default:
-               if (ASIC_IS_DCE5(rdev))
-                       return 4096 * 2;
-               else
-                       return 3840 * 2;
-       case 1:
-       case 5:
-               if (ASIC_IS_DCE5(rdev))
-                       return 6144 * 2;
-               else
-                       return 5760 * 2;
-       case 2:
-       case 6:
-               if (ASIC_IS_DCE5(rdev))
-                       return 8192 * 2;
-               else
-                       return 7680 * 2;
-       case 3:
-       case 7:
-               if (ASIC_IS_DCE5(rdev))
-                       return 2048 * 2;
-               else
-                       return 1920 * 2;
+       if (radeon_crtc->base.enabled && mode) {
+               switch (tmp) {
+               case 0:
+               case 4:
+               default:
+                       if (ASIC_IS_DCE5(rdev))
+                               return 4096 * 2;
+                       else
+                               return 3840 * 2;
+               case 1:
+               case 5:
+                       if (ASIC_IS_DCE5(rdev))
+                               return 6144 * 2;
+                       else
+                               return 5760 * 2;
+               case 2:
+               case 6:
+                       if (ASIC_IS_DCE5(rdev))
+                               return 8192 * 2;
+                       else
+                               return 7680 * 2;
+               case 3:
+               case 7:
+                       if (ASIC_IS_DCE5(rdev))
+                               return 2048 * 2;
+                       else
+                               return 1920 * 2;
+               }
        }
+
+       /* controller not enabled, so no lb used */
+       return 0;
 }
 
 static u32 evergreen_get_number_of_dram_channels(struct radeon_device *rdev)