Re: [PATCH] drm/amd/display: use correct scale for actual_brightness
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 > > Signed-off-by: Alexander Monakov > > --- > > .../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 0x > > -*/ > > - 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
Re: [PATCH] drm/amd/display: use correct scale for actual_brightness
On 2020-08-04 12:28 p.m., Alexander Monakov wrote: 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? Sorry, replied to the wrong email by accident here. The other change was modifying the max_brightness range and rescaling internal min/max defaults. I don't think it was sent out to the list yet. Regards, Nicholas Kazlauskas 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 Signed-off-by: Alexander Monakov --- .../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 0x -*/ - 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
Re: [PATCH] drm/amd/display: use correct scale for actual_brightness
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 Signed-off-by: Alexander Monakov Overall approach seems reasonable, nice catch. I suggest to add convert_to_user_brightness() instead of making from_user a flag and extending the current functionality though. It makes it more clear from the call site what's happening. Regards, Nicholas Kazlauskas --- .../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 0x -*/ - 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, , )) + 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)
Re: [PATCH] drm/amd/display: use correct scale for actual_brightness
This is a cleaner change the other proposed patch since it doesn't need to modify the exist conversion functions but I'd be worried about broken userspace relying on 0-255 as the only acceptable range. 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 Signed-off-by: Alexander Monakov --- .../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 0x -*/ - 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, , )) + 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
[PATCH] drm/amd/display: use correct scale for actual_brightness
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 Signed-off-by: Alexander Monakov --- .../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 0x -*/ - 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, , )) + 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(, bd->props.brightness); + brightness = convert_brightness(, bd->props.brightness, 1); // Change brightness based on AUX property if (caps.aux_support) return set_backlight_via_aux(link,