| Message ID | 20180824155402.2822-1-enric.balletbo@collabora.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | backlight: pwm_bl: Fix brightness levels for non-DT case. | expand |
Enric Balletbo i Serra <enric.balletbo@collabora.com> writes: > Commit '88ba95bedb79 ("backlight: pwm_bl: Compute brightness of LED > linearly to human eye")' allows the possibility to compute a default > brightness table when there isn't the brightness-levels property in the > DT. Unfortunately the changes made broke the pwm backlight for the > non-DT boards. > > Usually, the non-DT boards don't pass the brightness levels via platform > data, instead, they set the max_brightness in their platform data and the > driver calculates the level without a table. The ofending patch assumed > that when there is no brightness levels table we should create one, but this > is clearly wrong for the non-DT case. > > After this patch the code handles the DT and the non-DT case taking in > consideration also if max_brightness is set or not. The default table is > only created when neither, brightness-levels and max_brightness, are > set. > > The patch also fixes another issue found by Robert. Before this patch > looks like a division by 0 was possible when state.period returned 0 by > pwm_get_state(). This is because pwm_get_state() was called before > pwm_apply_args() so state.period was not initialized. The patch moves > the pwm_apply_args() call before any call to pwm_get_state(). > > Fixes: '88ba95bedb79 ("backlight: pwm_bl: Compute brightness of LED linearly to human eye")' > Reported-by: Robert Jarzmik <robert.jarzmik@free.fr> > Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com> Tested-by: Robert Jarzmik <robert.jarzmik@free.fr> Cheers. -- Robert
On 25/08/18 01:04, Robert Jarzmik wrote: > Enric Balletbo i Serra <enric.balletbo@collabora.com> writes: > >> Commit '88ba95bedb79 ("backlight: pwm_bl: Compute brightness of LED >> linearly to human eye")' allows the possibility to compute a default >> brightness table when there isn't the brightness-levels property in the >> DT. Unfortunately the changes made broke the pwm backlight for the >> non-DT boards. >> >> Usually, the non-DT boards don't pass the brightness levels via platform >> data, instead, they set the max_brightness in their platform data and the >> driver calculates the level without a table. The ofending patch assumed >> that when there is no brightness levels table we should create one, but this >> is clearly wrong for the non-DT case. >> >> After this patch the code handles the DT and the non-DT case taking in >> consideration also if max_brightness is set or not. The default table is >> only created when neither, brightness-levels and max_brightness, are >> set. >> >> The patch also fixes another issue found by Robert. Before this patch >> looks like a division by 0 was possible when state.period returned 0 by >> pwm_get_state(). This is because pwm_get_state() was called before >> pwm_apply_args() so state.period was not initialized. The patch moves >> the pwm_apply_args() call before any call to pwm_get_state(). >> >> Fixes: '88ba95bedb79 ("backlight: pwm_bl: Compute brightness of LED linearly to human eye")' >> Reported-by: Robert Jarzmik <robert.jarzmik@free.fr> >> Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com> > Tested-by: Robert Jarzmik <robert.jarzmik@free.fr> Acked-by: Daniel Thompson <daniel.thompson@linaro.org> (and sorry for the delay) Daniel.
diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c index bdfcc0a71db1..19770f7bffe4 100644 --- a/drivers/video/backlight/pwm_bl.c +++ b/drivers/video/backlight/pwm_bl.c @@ -539,7 +539,33 @@ static int pwm_backlight_probe(struct platform_device *pdev) dev_dbg(&pdev->dev, "got pwm for backlight\n"); - if (!data->levels) { + /* + * FIXME: pwm_apply_args() should be removed when switching to + * the atomic PWM API. + */ + pwm_apply_args(pb->pwm); + + if (data->levels) { + /* + * For the DT case, only when brightness levels is defined + * data->levels is filled. For the non-DT case, data->levels + * can come from platform data, however is not usual. + */ + for (i = 0; i <= data->max_brightness; i++) { + if (data->levels[i] > pb->scale) + pb->scale = data->levels[i]; + + pb->levels = data->levels; + } + } else if (!data->max_brightness) { + /* + * If no brightness levels are provided and max_brightness is + * not set, use the default brightness table. For the DT case, + * max_brightness is set to 0 when brightness levels is not + * specified. For the non-DT case, max_brightness is usually + * set to some value. + */ + /* Get the PWM period (in nanoseconds) */ pwm_get_state(pb->pwm, &state); @@ -550,21 +576,21 @@ static int pwm_backlight_probe(struct platform_device *pdev) "failed to setup default brightness table\n"); goto err_alloc; } - } - for (i = 0; i <= data->max_brightness; i++) { - if (data->levels[i] > pb->scale) - pb->scale = data->levels[i]; + for (i = 0; i <= data->max_brightness; i++) { + if (data->levels[i] > pb->scale) + pb->scale = data->levels[i]; - pb->levels = data->levels; + pb->levels = data->levels; + } + } else { + /* + * That only happens for the non-DT case, where platform data + * sets the max_brightness value. + */ + pb->scale = data->max_brightness; } - /* - * FIXME: pwm_apply_args() should be removed when switching to - * the atomic PWM API. - */ - pwm_apply_args(pb->pwm); - /* * The DT case will set the pwm_period_ns field to 0 and store the * period, parsed from the DT, in the PWM device. For the non-DT case,
Commit '88ba95bedb79 ("backlight: pwm_bl: Compute brightness of LED linearly to human eye")' allows the possibility to compute a default brightness table when there isn't the brightness-levels property in the DT. Unfortunately the changes made broke the pwm backlight for the non-DT boards. Usually, the non-DT boards don't pass the brightness levels via platform data, instead, they set the max_brightness in their platform data and the driver calculates the level without a table. The ofending patch assumed that when there is no brightness levels table we should create one, but this is clearly wrong for the non-DT case. After this patch the code handles the DT and the non-DT case taking in consideration also if max_brightness is set or not. The default table is only created when neither, brightness-levels and max_brightness, are set. The patch also fixes another issue found by Robert. Before this patch looks like a division by 0 was possible when state.period returned 0 by pwm_get_state(). This is because pwm_get_state() was called before pwm_apply_args() so state.period was not initialized. The patch moves the pwm_apply_args() call before any call to pwm_get_state(). Fixes: '88ba95bedb79 ("backlight: pwm_bl: Compute brightness of LED linearly to human eye")' Reported-by: Robert Jarzmik <robert.jarzmik@free.fr> Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com> --- drivers/video/backlight/pwm_bl.c | 50 ++++++++++++++++++++++++-------- 1 file changed, 38 insertions(+), 12 deletions(-)