Intel-GFX Archive on lore.kernel.org
 help / color / mirror / Atom feed
* [Intel-gfx] [PATCH] drm/i915: Fail if DSC compression requirement is less than platform supports
@ 2023-06-26  8:28 Stanislav Lisovskiy
  2023-06-26 11:06 ` [Intel-gfx] ✗ Fi.CI.CHECKPATCH: warning for " Patchwork
                   ` (6 more replies)
  0 siblings, 7 replies; 11+ messages in thread
From: Stanislav Lisovskiy @ 2023-06-26  8:28 UTC (permalink / raw)
  To: intel-gfx

Currently we just clamp that value to the highest supported one, however that
means, we are not able to fit this into our available bandwidth range, so we
might see glitches or FIFO underruns.
While choosing less compressed bpp than min bpp required to handle the mode is
harmless and might even save some bandwidth, choosing higher compressed bpp than
min bpp required to handle the required mode config, can cause issues.
So in that case lets just conclude that even with DSC, we are not able to comply
with bandwidth requirements and fail.

Signed-off-by: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>
---
 drivers/gpu/drm/i915/display/intel_dp.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
index 9f40da20e88d..8696a1f02805 100644
--- a/drivers/gpu/drm/i915/display/intel_dp.c
+++ b/drivers/gpu/drm/i915/display/intel_dp.c
@@ -713,8 +713,17 @@ u32 intel_dp_dsc_nearest_valid_bpp(struct drm_i915_private *i915, u32 bpp, u32 p
 
 		/*
 		 * According to BSpec, 27 is the max DSC output bpp,
-		 * 8 is the min DSC output bpp
+		 * 8 is the min DSC output bpp.
+		 * While we can still clamp higher bpp values to 27, saving bandwidth,
+		 * if it is required to oompress up to bpp < 8, means we can't do
+		 * that and probably means we can't fit the required mode, even with
+		 * DSC enabled.
 		 */
+		if (bits_per_pixel < 8) {
+			drm_dbg_kms(&i915->drm, "Unsupported BPP %u, min 8\n",
+				    bits_per_pixel);
+			return 0;
+		}
 		bits_per_pixel = clamp_t(u32, bits_per_pixel, 8, 27);
 	} else {
 		/* Find the nearest match in the array of known BPPs from VESA */
-- 
2.37.3


^ permalink raw reply related	[flat|nested] 11+ messages in thread
* [Intel-gfx] [PATCH] drm/i915: Fail if DSC compression requirement is less than platform supports
@ 2023-06-29 12:25 Stanislav Lisovskiy
  2023-06-29 13:07 ` Luca Coelho
  0 siblings, 1 reply; 11+ messages in thread
From: Stanislav Lisovskiy @ 2023-06-29 12:25 UTC (permalink / raw)
  To: intel-gfx

Currently we just clamp that value to the highest supported one, however that
means, we are not able to fit this into our available bandwidth range, so we
might see glitches or FIFO underruns.
While choosing less compressed bpp than min bpp required to handle the mode is
harmless and might even save some bandwidth, choosing higher compressed bpp than
min bpp required to handle the required mode config, can cause issues.
So in that case lets just conclude that even with DSC, we are not able to comply
with bandwidth requirements and fail.

v2: - s/clamp_t/min_t/ (Luca Coelho)

Signed-off-by: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>
---
 drivers/gpu/drm/i915/display/intel_dp.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
index 9f40da20e88d..03675620e3ea 100644
--- a/drivers/gpu/drm/i915/display/intel_dp.c
+++ b/drivers/gpu/drm/i915/display/intel_dp.c
@@ -713,9 +713,18 @@ u32 intel_dp_dsc_nearest_valid_bpp(struct drm_i915_private *i915, u32 bpp, u32 p
 
 		/*
 		 * According to BSpec, 27 is the max DSC output bpp,
-		 * 8 is the min DSC output bpp
+		 * 8 is the min DSC output bpp.
+		 * While we can still clamp higher bpp values to 27, saving bandwidth,
+		 * if it is required to oompress up to bpp < 8, means we can't do
+		 * that and probably means we can't fit the required mode, even with
+		 * DSC enabled.
 		 */
-		bits_per_pixel = clamp_t(u32, bits_per_pixel, 8, 27);
+		if (bits_per_pixel < 8) {
+			drm_dbg_kms(&i915->drm, "Unsupported BPP %u, min 8\n",
+				    bits_per_pixel);
+			return 0;
+		}
+		bits_per_pixel = min_t(u32, bits_per_pixel, 27);
 	} else {
 		/* Find the nearest match in the array of known BPPs from VESA */
 		for (i = 0; i < ARRAY_SIZE(valid_dsc_bpp) - 1; i++) {
-- 
2.37.3


^ permalink raw reply related	[flat|nested] 11+ messages in thread
end of thread, other threads:[~2023-06-29 13:08 UTC | newest]

Thread overview: 11+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2023-06-26  8:28 [Intel-gfx] [PATCH] drm/i915: Fail if DSC compression requirement is less than platform supports Stanislav Lisovskiy
2023-06-26 11:06 ` [Intel-gfx] ✗ Fi.CI.CHECKPATCH: warning for " Patchwork
2023-06-26 11:16 ` [Intel-gfx] ✓ Fi.CI.BAT: success " Patchwork
2023-06-26 12:18 ` [Intel-gfx] [PATCH] " Luca Coelho
2023-06-26 13:52   ` Lisovskiy, Stanislav
2023-06-26 19:14 ` [Intel-gfx] ✗ Fi.CI.IGT: failure for " Patchwork
2023-06-28 16:04 ` [Intel-gfx] ✗ Fi.CI.CHECKPATCH: warning for drm/i915: Fail if DSC compression requirement is less than platform supports (rev2) Patchwork
2023-06-28 16:20 ` [Intel-gfx] ✓ Fi.CI.BAT: success " Patchwork
2023-06-29  9:45 ` [Intel-gfx] ✗ Fi.CI.IGT: failure " Patchwork
  -- strict thread matches above, loose matches on Subject: below --
2023-06-29 12:25 [Intel-gfx] [PATCH] drm/i915: Fail if DSC compression requirement is less than platform supports Stanislav Lisovskiy
2023-06-29 13:07 ` Luca Coelho

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox