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Message-ID:
<CAGwozwH7m5CgGiK5Xu_q0JbJvRQbcHkgQd9nFXJNq3DQhWO7QQ@mail.gmail.com>
Date: Sun, 24 Aug 2025 21:33:47 +0200
From: Antheas Kapenekakis <lkml@...heas.dev>
To: amd-gfx@...ts.freedesktop.org
Cc: dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
Alex Deucher <alexander.deucher@....com>,
Christian König <christian.koenig@....com>,
David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
Harry Wentland <harry.wentland@....com>,
Rodrigo Siqueira <siqueira@...lia.com>,
Mario Limonciello <mario.limonciello@....com>, Peyton Lee <peytolee@....com>,
Lang Yu <lang.yu@....com>
Subject: Re: [PATCH v1 2/2] drm/amd/display: Adjust AUX brightness to be a
granularity of 100
On Sun, 24 Aug 2025 at 10:54, Antheas Kapenekakis <lkml@...heas.dev> wrote:
>
> Certain OLED devices malfunction on specific brightness levels.
> Specifically, when DP_SOURCE_BACKLIGHT_LEVEL is written to with
> the minor byte being 0x00 and sometimes 0x01, the panel forcibly
> turns off until the device sleeps again. This is an issue on
> multiple handhelds, including OneXPlayer F1 Pro and Ayaneo 3
> (the panel is suspected to be the same-1080p 7in OLED).
>
> Below are some examples. This was found by iterating over brighness
> ranges while printing DP_SOURCE_BACKLIGHT_LEVEL. It was found that
> the screen would malfunction on specific values, and some of them
> were collected.
>
> Broken:
> 86016: 10101000000000000
> 86272: 10101000100000000
> 87808: 10101011100000000
> 251648: 111101011100000000
> 251649: 111101011100000001
>
> Working:
> 86144: 10101000010000000
> 87809: 10101011100000001
> 251650: 111101011100000010
>
> The reason for this is that the range manipulation is too granular.
> AUX is currently written to with a granularity of 1. Forcing 100,
> which on the Ayaneo 3 OLED yields 400*10=4000 values, is plenty of
> granularity and fixes this issue. Iterating over the values through
> Python shows that the final byte is never 0x00, and testing over the
> entire range with a cadence of 0.2s/it and 73 increments (to saturate
> the range) shows no issues. Windows likewise shows no issues.
Well Phil managed to fall into the value 332800, which has a 0 minor
bit. Unfortunate. In hindsight, every 256 hundreds there would be a
zero anyway.
Before I made this patch I made a partial refactor of panel-quirks
where a quirk like this could go to. But I would really prefer not to
do quirks. Ill send that too.
Antheas
> Closes: https://gitlab.freedesktop.org/drm/amd/-/issues/3803
> Signed-off-by: Antheas Kapenekakis <lkml@...heas.dev>
> ---
> .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 28 +++++++++++--------
> 1 file changed, 17 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> index cd0e2976e268..bb16adcafb88 100644
> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> @@ -4739,7 +4739,8 @@ static void amdgpu_dm_update_backlight_caps(struct amdgpu_display_manager *dm,
> }
>
> static int get_brightness_range(const struct amdgpu_dm_backlight_caps *caps,
> - unsigned int *min, unsigned int *max)
> + unsigned int *min, unsigned int *max,
> + unsigned int *multiple)
> {
> if (!caps)
> return 0;
> @@ -4748,10 +4749,12 @@ static int get_brightness_range(const struct amdgpu_dm_backlight_caps *caps,
> // Firmware limits are in nits, DC API wants millinits.
> *max = 1000 * caps->aux_max_input_signal;
> *min = 1000 * caps->aux_min_input_signal;
> + *multiple = 100;
> } else {
> // Firmware limits are 8-bit, PWM control is 16-bit.
> *max = 0x101 * caps->max_input_signal;
> *min = 0x101 * caps->min_input_signal;
> + *multiple = 1;
> }
> return 1;
> }
> @@ -4813,23 +4816,25 @@ static void convert_custom_brightness(const struct amdgpu_dm_backlight_caps *cap
> static u32 convert_brightness_from_user(const struct amdgpu_dm_backlight_caps *caps,
> uint32_t brightness)
> {
> - unsigned int min, max;
> + unsigned int min, max, multiple;
>
> - if (!get_brightness_range(caps, &min, &max))
> + if (!get_brightness_range(caps, &min, &max, &multiple))
> return brightness;
>
> convert_custom_brightness(caps, min, max, &brightness);
>
> - // Rescale 0..max to min..max
> - return min + DIV_ROUND_CLOSEST_ULL((u64)(max - min) * brightness, max);
> + // Rescale 0..max to min..max rounding to nearest multiple
> + return rounddown(
> + min + DIV_ROUND_CLOSEST_ULL((u64)(max - min) * brightness, max),
> + multiple);
> }
>
> static u32 convert_brightness_to_user(const struct amdgpu_dm_backlight_caps *caps,
> uint32_t brightness)
> {
> - unsigned int min, max;
> + unsigned int min, max, multiple;
>
> - if (!get_brightness_range(caps, &min, &max))
> + if (!get_brightness_range(caps, &min, &max, &multiple))
> return brightness;
>
> if (brightness < min)
> @@ -4970,7 +4975,7 @@ amdgpu_dm_register_backlight_device(struct amdgpu_dm_connector *aconnector)
> struct backlight_properties props = { 0 };
> struct amdgpu_dm_backlight_caps *caps;
> char bl_name[16];
> - int min, max;
> + int min, max, multiple;
>
> if (aconnector->bl_idx == -1)
> return;
> @@ -4983,15 +4988,16 @@ amdgpu_dm_register_backlight_device(struct amdgpu_dm_connector *aconnector)
> }
>
> caps = &dm->backlight_caps[aconnector->bl_idx];
> - if (get_brightness_range(caps, &min, &max)) {
> + if (get_brightness_range(caps, &min, &max, &multiple)) {
> if (power_supply_is_system_supplied() > 0)
> props.brightness = DIV_ROUND_CLOSEST((max - min) * caps->ac_level, 100);
> else
> props.brightness = DIV_ROUND_CLOSEST((max - min) * caps->dc_level, 100);
> /* min is zero, so max needs to be adjusted */
> props.max_brightness = max - min;
> - drm_dbg(drm, "Backlight caps: min: %d, max: %d, ac %d, dc %d\n", min, max,
> - caps->ac_level, caps->dc_level);
> + drm_dbg(drm,
> + "Backlight caps: min: %d, max: %d, ac %d, dc %d, multiple: %d\n",
> + min, max, caps->ac_level, caps->dc_level, multiple);
> } else
> props.brightness = props.max_brightness = MAX_BACKLIGHT_LEVEL;
>
> --
> 2.50.1
>
>
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