From: Alexander Monakov <amonakov@xxxxxxxxx> commit 69d9f4278d0f9d24607645f10e5ac5c59c77a4ac upstream. Documentation for sysfs backlight level interface requires that values in both 'brightness' and 'actual_brightness' files are interpreted to be in range from 0 to the value given in the 'max_brightness' file. With amdgpu, max_brightness gives 255, and values written by the user into 'brightness' are internally rescaled to a wider range. However, reading from 'actual_brightness' gives the raw register value without inverse rescaling. This causes issues for various userspace tools such as PowerTop and systemd that expect the value to be in the correct range. Introduce a helper to retrieve internal backlight range. Use it to reimplement 'convert_brightness' as 'convert_brightness_from_user' and introduce 'convert_brightness_to_user'. Bug: https://bugzilla.kernel.org/show_bug.cgi?id=203905 Bug: https://gitlab.freedesktop.org/drm/amd/-/issues/1242 Cc: Alex Deucher <alexander.deucher@xxxxxxx> Cc: Nicholas Kazlauskas <nicholas.kazlauskas@xxxxxxx> Reviewed-by: Alex Deucher <alexander.deucher@xxxxxxx> Signed-off-by: Alexander Monakov <amonakov@xxxxxxxxx> Signed-off-by: Alex Deucher <alexander.deucher@xxxxxxx> Cc: stable@xxxxxxxxxxxxxxx Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 81 ++++++++++------------ 1 file changed, 40 insertions(+), 41 deletions(-) --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c @@ -2882,51 +2882,50 @@ static int set_backlight_via_aux(struct return rc ? 0 : 1; } -static u32 convert_brightness(const struct amdgpu_dm_backlight_caps *caps, - const uint32_t user_brightness) +static int get_brightness_range(const struct amdgpu_dm_backlight_caps *caps, + unsigned *min, unsigned *max) { - u32 min, max, conversion_pace; - u32 brightness = user_brightness; - if (!caps) - goto out; + return 0; - if (!caps->aux_support) { - max = caps->max_input_signal; - min = caps->min_input_signal; - /* - * The brightness input is in the range 0-255 - * It needs to be rescaled to be between the - * requested min and max input signal - * It also needs to be scaled up by 0x101 to - * match the DC interface which has a range of - * 0 to 0xffff - */ - conversion_pace = 0x101; - brightness = - user_brightness - * conversion_pace - * (max - min) - / AMDGPU_MAX_BL_LEVEL - + min * conversion_pace; + if (caps->aux_support) { + // Firmware limits are in nits, DC API wants millinits. + *max = 1000 * caps->aux_max_input_signal; + *min = 1000 * caps->aux_min_input_signal; } else { - /* TODO - * We are doing a linear interpolation here, which is OK but - * does not provide the optimal result. We probably want - * something close to the Perceptual Quantizer (PQ) curve. - */ - max = caps->aux_max_input_signal; - min = caps->aux_min_input_signal; - - brightness = (AMDGPU_MAX_BL_LEVEL - user_brightness) * min - + user_brightness * max; - // Multiple the value by 1000 since we use millinits - brightness *= 1000; - brightness = DIV_ROUND_CLOSEST(brightness, AMDGPU_MAX_BL_LEVEL); + // Firmware limits are 8-bit, PWM control is 16-bit. + *max = 0x101 * caps->max_input_signal; + *min = 0x101 * caps->min_input_signal; } + return 1; +} + +static u32 convert_brightness_from_user(const struct amdgpu_dm_backlight_caps *caps, + uint32_t brightness) +{ + unsigned min, max; + + if (!get_brightness_range(caps, &min, &max)) + return brightness; + + // Rescale 0..255 to min..max + return min + DIV_ROUND_CLOSEST((max - min) * brightness, + AMDGPU_MAX_BL_LEVEL); +} + +static u32 convert_brightness_to_user(const struct amdgpu_dm_backlight_caps *caps, + uint32_t brightness) +{ + unsigned min, max; + + if (!get_brightness_range(caps, &min, &max)) + return brightness; -out: - return brightness; + if (brightness < min) + return 0; + // Rescale min..max to 0..255 + return DIV_ROUND_CLOSEST(AMDGPU_MAX_BL_LEVEL * (brightness - min), + max - min); } static int amdgpu_dm_backlight_update_status(struct backlight_device *bd) @@ -2942,7 +2941,7 @@ static int amdgpu_dm_backlight_update_st link = (struct dc_link *)dm->backlight_link; - brightness = convert_brightness(&caps, bd->props.brightness); + brightness = convert_brightness_from_user(&caps, bd->props.brightness); // Change brightness based on AUX property if (caps.aux_support) return set_backlight_via_aux(link, brightness); @@ -2959,7 +2958,7 @@ static int amdgpu_dm_backlight_get_brigh if (ret == DC_ERROR_UNEXPECTED) return bd->props.brightness; - return ret; + return convert_brightness_to_user(&dm->backlight_caps, ret); } static const struct backlight_ops amdgpu_dm_backlight_ops = {
