Message-Id: <20250601232937.3510379-56-sashal@kernel.org>
Date: Sun,  1 Jun 2025 19:28:48 -0400
From: Sasha Levin <sashal@...nel.org>
To: patches@...ts.linux.dev,
	stable@...r.kernel.org
Cc: Samson Tam <Samson.Tam@....com>,
	Alvin Lee <alvin.lee2@....com>,
	Ray Wu <ray.wu@....com>,
	Daniel Wheeler <daniel.wheeler@....com>,
	Alex Deucher <alexander.deucher@....com>,
	Sasha Levin <sashal@...nel.org>,
	harry.wentland@....com,
	sunpeng.li@....com,
	christian.koenig@....com,
	airlied@...il.com,
	simona@...ll.ch,
	jun.lei@....com,
	alex.hung@....com,
	navid.assadian@....com,
	Relja.Vojvodic@....com,
	wenjing.liu@....com,
	amd-gfx@...ts.freedesktop.org,
	dri-devel@...ts.freedesktop.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH AUTOSEL 6.14 056/102] drm/amd/display: disable EASF narrow filter sharpening

From: Samson Tam <Samson.Tam@....com>

[ Upstream commit c8d7e0be8183f4375a5cf5c3efd0c678129ea4de ]

[Why & How]
Default should be 1 to disable EASF narrow filter sharpening.

Reviewed-by: Alvin Lee <alvin.lee2@....com>
Signed-off-by: Samson Tam <Samson.Tam@....com>
Signed-off-by: Ray Wu <ray.wu@....com>
Tested-by: Daniel Wheeler <daniel.wheeler@....com>
Signed-off-by: Alex Deucher <alexander.deucher@....com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---

Now I have a complete picture. Based on my analysis, I can provide the
final backporting recommendation: ## **BACKPORTING ANALYSIS:
drm/amd/display: disable EASF narrow filter sharpening** ###
**RECOMMENDATION: YES** ### **Analysis Summary:** **Commit Details:** -
**Commit ID:** c8d7e0be8183f4375a5cf5c3efd0c678129ea4de - **Author:**
Samson Tam <Samson.Tam@....com> - **Date:** Thu May 1 15:59:47 2025
-0400 - **Subject:** drm/amd/display: disable EASF narrow filter
sharpening - **Files Changed:**
`drivers/gpu/drm/amd/display/dc/sspl/dc_spl.c` (2 lines) **Technical
Changes:** The commit makes a simple but important change: - **Line
1302:** `easf_v_sharp_factor = 0` → `easf_v_sharp_factor = 1` - **Line
1466:** `easf_h_sharp_factor = 0` → `easf_h_sharp_factor = 1` **Why This
Is A Bug Fix:** 1. **Intent vs Implementation Mismatch:** The commit
message clearly states "Default should be 1 to disable EASF narrow
filter sharpening" 2. **Hardware Behavior:** These sharp_factor
variables control AMD display hardware's 2-tap sharp filtering: - Value
0001-Fix-Clippy-warnings.patch 0002-Enhance-inference-prompt-to-utilize-
CVEKERNELDIR-whe.patch 0003-Update-to-latest-version-of-clap.patch
drm_amd_display_vertical_interrupt_dcn32_dcn401_backport_analysis.md =
sharpening **enabled** - Value 0001-Fix-Clippy-warnings.patch
drm_amd_display_vertical_interrupt_dcn32_dcn401_backport_analysis.md
gfx_v12_userq_eop_interrupt_handling_backport_analysis.md
verisilicon_av1_4k_analysis.md = sharpening **disabled** 3.
**Consistency Fix:** Prior to this fix, the code was unintentionally
enabling sharpening when it should have been disabled by default
**Stability and Risk Assessment:** - **LOW RISK:** Disables a feature
rather than enabling new functionality - **IMPROVES STABILITY:**
Prevents potential display artifacts from unwanted sharpening -
**MINIMAL SCOPE:** Only affects EASF (Edge Adaptive Scaler Filter)
narrow filter functionality - **WELL-TESTED:** Has proper review chain
(Reviewed-by: Alvin Lee, Tested-by: Daniel Wheeler) **Backporting
Criteria Analysis:** ✅ **Fixes Important Bug:** Corrects unintended
feature activation that could cause display issues ✅ **Minimal Risk:**
Simple value change, disables rather than enables functionality ✅ **No
New Features:** Pure bug fix, no new architectural changes ✅ **Well-
Contained:** Limited to AMD display driver's scaling/filtering subsystem
✅ **Stable Tree Appropriate:** Improves hardware behavior consistency
**Comparison to Historical Similar Commits:** Looking at the provided
historical commits that were marked "NO" for backporting: - Those were
typically **feature additions** or **complex policy changes** - This
commit is fundamentally different: it's a **simple bug fix** that
corrects default behavior - Unlike feature commits, this **improves
stability** by disabling problematic functionality **Conclusion:** This
commit should be backported to stable kernels. It fixes a bug where EASF
narrow filter sharpening was unintentionally enabled by default when
AMD's design intent was to have it disabled. The fix is low-risk, well-
tested, and improves display subsystem stability by preventing potential
artifacts from unwanted sharpening algorithms. **Final Answer: YES** -
This commit meets all criteria for stable kernel backporting.

 drivers/gpu/drm/amd/display/dc/spl/dc_spl.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/amd/display/dc/spl/dc_spl.c b/drivers/gpu/drm/amd/display/dc/spl/dc_spl.c
index 047f05ab01810..5fb6c4b7410bf 100644
--- a/drivers/gpu/drm/amd/display/dc/spl/dc_spl.c
+++ b/drivers/gpu/drm/amd/display/dc/spl/dc_spl.c
@@ -1292,7 +1292,7 @@ static void spl_set_easf_data(struct spl_scratch *spl_scratch, struct spl_out *s
 	if (enable_easf_v) {
 		dscl_prog_data->easf_v_en = true;
 		dscl_prog_data->easf_v_ring = 0;
-		dscl_prog_data->easf_v_sharp_factor = 0;
+		dscl_prog_data->easf_v_sharp_factor = 1;
 		dscl_prog_data->easf_v_bf1_en = 1;	// 1-bit, BF1 calculation enable, 0=disable, 1=enable
 		dscl_prog_data->easf_v_bf2_mode = 0xF;	// 4-bit, BF2 calculation mode
 		/* 2-bit, BF3 chroma mode correction calculation mode */
@@ -1456,7 +1456,7 @@ static void spl_set_easf_data(struct spl_scratch *spl_scratch, struct spl_out *s
 	if (enable_easf_h) {
 		dscl_prog_data->easf_h_en = true;
 		dscl_prog_data->easf_h_ring = 0;
-		dscl_prog_data->easf_h_sharp_factor = 0;
+		dscl_prog_data->easf_h_sharp_factor = 1;
 		dscl_prog_data->easf_h_bf1_en =
 			1;	// 1-bit, BF1 calculation enable, 0=disable, 1=enable
 		dscl_prog_data->easf_h_bf2_mode =
-- 
2.39.5

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