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FAILED: patch "[PATCH] drm/amd/display: Scale custom brightness curve from full" failed to apply to 7.2-stable tree

PATCH Applied [email protected] 3 participants 3 messages Sep 9 – Sep 11

Subsystems (4)
Stable branch DRM drivers Radeon and amdgpu DRM drivers AMD display core
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[email protected]

author maintainer
#0 lore raw

The patch below does not apply to the 7.2-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-7.2.y
git checkout FETCH_HEAD
git cherry-pick -x 6fd83a1c2cdea48c396f600795217fbdfb8124f6
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026090900-astrology-gallery-8428@gregkh' --subject-prefix 'PATCH 7.2.y' 'HEAD^..'

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 6fd83a1c2cdea48c396f600795217fbdfb8124f6 Mon Sep 17 00:00:00 2001
From: Akhmed Zhitaev <[email protected]>
Date: Thu, 13 Aug 2026 22:09:59 +0500
Subject: [PATCH] drm/amd/display: Scale custom brightness curve from full
range

Custom brightness curves use an 8-bit input signal. After exporting the full PWM range to userspace, the curve normalizer still divides requests by the physical PWM span. On panels with a nonzero minimum PWM level, this can produce a curve input greater than 255 and send an invalid backlight level to DC.

Scale the userspace [0..max] range to the curve's [0..255] range instead. This retains the full advertised range and keeps the reverse readback conversion unchanged.

Fixes 8dbd72cb7900 ("drm/amd/display: Export full brightness range to userspace")
Cc [email protected]
Signed-off-by Akhmed Zhitaev <[email protected]>
Reviewed-by Mario Limonciello (AMD) <[email protected]>

(Move to amdgpu_dm_backlight.c)

Link https://patch.msgid.link/[email protected] open here
Signed-off-by Mario Limonciello <[email protected]>
Signed-off-by Alex Deucher <[email protected]>
drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_backlight.c +4 -4
index b66ca60e697d..e61bbc310f33 100644
@@ -106,10 +106,10 @@ int get_brightness_range(const struct amdgpu_dm_backlight_caps *caps,
 }
 EXPORT_IF_KUNIT(get_brightness_range);
 
-/* Rescale from [min..max] to [0..AMDGPU_MAX_BL_LEVEL] */
-static inline u32 scale_input_to_fw(int min, int max, u64 input)
+/* Rescale userspace [0..max] to the firmware curve's [0..255]. */
+static inline u32 scale_input_to_fw(int max, u64 input)
 {
-	return DIV_ROUND_CLOSEST_ULL(input * AMDGPU_MAX_BL_LEVEL, max - min);
+	return DIV_ROUND_CLOSEST_ULL(input * AMDGPU_MAX_BL_LEVEL, max);
 }
 
 /* Rescale from [0..AMDGPU_MAX_BL_LEVEL] to [min..max] */

@@ -123,7 +123,7 @@ void convert_custom_brightness(const struct amdgpu_dm_backlight_caps *caps,
 			       unsigned int min, unsigned int max,
 			       uint32_t *user_brightness)
 {
-	u32 brightness = scale_input_to_fw(min, max, *user_brightness);
+	u32 brightness = scale_input_to_fw(max, *user_brightness);
 	u8 lower_signal, upper_signal, upper_lum, lower_lum, lum;
 	int left, right;
#1 lore raw

PATCH 1/1 drm/amd/display: Scale custom brightness curve from full range

Custom brightness curves use an 8-bit input signal. After exporting the full PWM range to userspace, the curve normalizer still divides requests by the physical PWM span. On panels with a nonzero minimum PWM level, this can produce a curve input greater than 255 and send an invalid backlight level to DC.

Scale the userspace [0..max] range to the curve's [0..255] range instead. This retains the full advertised range and keeps the reverse readback conversion unchanged.

Fixes 8dbd72cb7900 ("drm/amd/display: Export full brightness range to userspace")
Cc [email protected]
Signed-off-by Akhmed Zhitaev <[email protected]>
Reviewed-by Mario Limonciello (AMD) <[email protected]>

(Move to amdgpu_dm_backlight.c)

Link https://patch.msgid.link/[email protected] open here
Signed-off-by Mario Limonciello <[email protected]>
Signed-off-by Alex Deucher <[email protected]>
(cherry picked from commit 6fd83a1c2cdea48c396f600795217fbdfb8124f6)
---
 drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)
drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c +4 -4
index 9320e49e44..b5618df4ed 100644
@@ -5265,10 +5265,10 @@ static int get_brightness_range(const struct amdgpu_dm_backlight_caps *caps,
 	return 1;
 }
 
-/* Rescale from [min..max] to [0..AMDGPU_MAX_BL_LEVEL] */
-static inline u32 scale_input_to_fw(int min, int max, u64 input)
+/* Rescale userspace [0..max] to the firmware curve's [0..255]. */
+static inline u32 scale_input_to_fw(int max, u64 input)
 {
-	return DIV_ROUND_CLOSEST_ULL(input * AMDGPU_MAX_BL_LEVEL, max - min);
+	return DIV_ROUND_CLOSEST_ULL(input * AMDGPU_MAX_BL_LEVEL, max);
 }
 
 /* Rescale from [0..AMDGPU_MAX_BL_LEVEL] to [min..max] */

@@ -5281,7 +5281,7 @@ static void convert_custom_brightness(const struct amdgpu_dm_backlight_caps *cap
 				      unsigned int min, unsigned int max,
 				      uint32_t *user_brightness)
 {
-	u32 brightness = scale_input_to_fw(min, max, *user_brightness);
+	u32 brightness = scale_input_to_fw(max, *user_brightness);
 	u8 lower_signal, upper_signal, upper_lum, lower_lum, lum;
 	int left, right;
Signature · 1 line
2.55.0
maintainer Applied
#2 lore raw

Re: [PATCH 7.2.y] drm/amd/display: Scale custom brightness curve from full range

Quoted 3 lines

Custom brightness curves use an 8-bit input signal. After exporting the full PWM range to userspace, the curve normalizer still divides requests by the physical PWM span.

Queued for 7.2, thanks.

Signature · 2 lines
Thanks,
Sasha