On Tue, 4 Aug 2020, Kazlauskas, Nicholas wrote: > This is a cleaner change the other proposed patch since it doesn't need to Can you give a URL to the other patch please? > modify the exist conversion functions but I'd be worried about broken > userspace relying on 0-255 as the only acceptable range. Not sure what you mean by this. Userspace simply reads the maximum value from max_brightness sysfs file. On other gpu/firmware combinations it can be 7 or 9 for example, it just happens to be 255 with modern amdgpu. Minimum value is always zero. Value seen in max_brightness remains 255 with this patch, so as far as userspace is concerned nothing is changed apart from value given by actual_brightness file. Alexander > > Not an expert on existing implementations to point out a specific one though. > > Regards, > Nicholas Kazlauskas > > On 2020-08-03 4:02 p.m., Alexander Monakov wrote: > > 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. Extend the > > existing 'convert_brightness' function to handle conversion in both > > directions. > > > > 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> > > Signed-off-by: Alexander Monakov <amonakov@xxxxxxxxx> > > --- > > .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 73 ++++++++----------- > > 1 file changed, 32 insertions(+), 41 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 710edc70e37e..03e21e7b7917 100644 > > --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c > > +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c > > @@ -2881,51 +2881,42 @@ static int set_backlight_via_aux(struct dc_link > > *link, uint32_t brightness) > > 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; > > +} > > -out: > > - return brightness; > > +static u32 convert_brightness(const struct amdgpu_dm_backlight_caps *caps, > > + const uint32_t brightness, int from_user) > > +{ > > + unsigned min, max; > > + > > + if (!get_brightness_range(caps, &min, &max)) > > + return brightness; > > + > > + if (from_user) > > + // Rescale 0..255 to min..max > > + return min + DIV_ROUND_CLOSEST((max - min) * brightness, > > + AMDGPU_MAX_BL_LEVEL); > > + > > + 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) > > @@ -2941,7 +2932,7 @@ static int amdgpu_dm_backlight_update_status(struct > > backlight_device *bd) > > link = (struct dc_link *)dm->backlight_link; > > - brightness = convert_brightness(&caps, bd->props.brightness); > > + brightness = convert_brightness(&caps, bd->props.brightness, 1); > > // Change brightness based on AUX property > > if (caps.aux_support) > > return set_backlight_via_aux(link, brightness); > > @@ -2958,7 +2949,7 @@ static int amdgpu_dm_backlight_get_brightness(struct > > backlight_device *bd) > > if (ret == DC_ERROR_UNEXPECTED) > > return bd->props.brightness; > > - return ret; > > + return convert_brightness(&dm->backlight_caps, ret, 0); > > } > > static const struct backlight_ops amdgpu_dm_backlight_ops = { > > > > base-commit: bcf876870b95592b52519ed4aafcf9d95999bc9c > > > > _______________________________________________ amd-gfx mailing list amd-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/amd-gfx
