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>

1 files changed, 44 insertions, 45 deletions

diff --git a/drivers/gpu/drm/radeon/evergreen.c b/drivers/gpu/drm/radeon/evergreen.c
index 3453910ee0f3..43fd01674489 100644
--- 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)