| Message ID | 20210708091058.56317-1-marex@denx.de (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | video: backlight: Only set maximum brightness for gpio-backlight | expand |
On Thu, Jul 08, 2021 at 11:10:58AM +0200, Marek Vasut wrote: > The note in c2adda27d202f ("video: backlight: Add of_find_backlight helper > in backlight.c") says that gpio-backlight uses brightness as power state. > Other backlight drivers do not, so limit this workaround to gpio-backlight. > > This fixes the case where e.g. pwm-backlight can perfectly well be set to > brightness 0 on boot in DT, which without this patch leads to the display > brightness to be max instead of off. > > Fixes: c2adda27d202f ("video: backlight: Add of_find_backlight helper in backlight.c") > Signed-off-by: Marek Vasut <marex@denx.de> > Cc: Daniel Thompson <daniel.thompson@linaro.org> > Cc: Meghana Madhyastha <meghana.madhyastha@gmail.com> > Cc: Noralf Trønnes <noralf@tronnes.org> > Cc: Sean Paul <seanpaul@chromium.org> > Cc: Thierry Reding <treding@nvidia.com> I have to admit that this patch really does makes it clear just how nasty the hack in of_find_backlight() currently is. Moreover I think it is also be obsolete. gpio-backlight power mode handling was pretty broken when this code was introduced. It was fixed in 2019 by ec665b756e6f ("backlight: gpio backlight: Correct initial power state handling") by trying to match the behaviour of PWM backlight. The new code always sets the brightness to 1 so I think we can just remove the hack from of_find_backlight() since I think it is unreachable. Daniel. > --- > drivers/video/backlight/backlight.c | 5 ++++- > 1 file changed, 4 insertions(+), 1 deletion(-) > > diff --git a/drivers/video/backlight/backlight.c b/drivers/video/backlight/backlight.c > index 537fe1b376ad7..dfb66171dec41 100644 > --- a/drivers/video/backlight/backlight.c > +++ b/drivers/video/backlight/backlight.c > @@ -676,6 +676,7 @@ EXPORT_SYMBOL(of_find_backlight_by_node); > static struct backlight_device *of_find_backlight(struct device *dev) > { > struct backlight_device *bd = NULL; > + bool is_gpio_backlight = false; > struct device_node *np; > > if (!dev) > @@ -685,6 +686,8 @@ static struct backlight_device *of_find_backlight(struct device *dev) > np = of_parse_phandle(dev->of_node, "backlight", 0); > if (np) { > bd = of_find_backlight_by_node(np); > + is_gpio_backlight = > + of_device_is_compatible(np, "gpio-backlight"); > of_node_put(np); > if (!bd) > return ERR_PTR(-EPROBE_DEFER); > @@ -692,7 +695,7 @@ static struct backlight_device *of_find_backlight(struct device *dev) > * Note: gpio_backlight uses brightness as > * power state during probe > */ > - if (!bd->props.brightness) > + if (is_gpio_backlight && !bd->props.brightness) > bd->props.brightness = bd->props.max_brightness; > } > } > -- > 2.30.2
On 7/9/21 1:03 PM, Daniel Thompson wrote: > On Thu, Jul 08, 2021 at 11:10:58AM +0200, Marek Vasut wrote: >> The note in c2adda27d202f ("video: backlight: Add of_find_backlight helper >> in backlight.c") says that gpio-backlight uses brightness as power state. >> Other backlight drivers do not, so limit this workaround to gpio-backlight. >> >> This fixes the case where e.g. pwm-backlight can perfectly well be set to >> brightness 0 on boot in DT, which without this patch leads to the display >> brightness to be max instead of off. >> >> Fixes: c2adda27d202f ("video: backlight: Add of_find_backlight helper in backlight.c") >> Signed-off-by: Marek Vasut <marex@denx.de> >> Cc: Daniel Thompson <daniel.thompson@linaro.org> >> Cc: Meghana Madhyastha <meghana.madhyastha@gmail.com> >> Cc: Noralf Trønnes <noralf@tronnes.org> >> Cc: Sean Paul <seanpaul@chromium.org> >> Cc: Thierry Reding <treding@nvidia.com> > > I have to admit that this patch really does makes it clear just how > nasty the hack in of_find_backlight() currently is. > > Moreover I think it is also be obsolete. gpio-backlight power mode > handling was pretty broken when this code was introduced. It was fixed > in 2019 by ec665b756e6f ("backlight: gpio backlight: Correct initial > power state handling") by trying to match the behaviour of PWM > backlight. The new code always sets the brightness to 1 so I think we > can just remove the hack from of_find_backlight() since I think it is > unreachable. I assume by "new code" you mean the fixed gpio-backlight driver ? Dropping the whole code after the Note: is fine by me.
Den 09.07.2021 15.19, skrev Marek Vasut: > On 7/9/21 1:03 PM, Daniel Thompson wrote: >> On Thu, Jul 08, 2021 at 11:10:58AM +0200, Marek Vasut wrote: >>> The note in c2adda27d202f ("video: backlight: Add of_find_backlight >>> helper >>> in backlight.c") says that gpio-backlight uses brightness as power >>> state. >>> Other backlight drivers do not, so limit this workaround to >>> gpio-backlight. >>> >>> This fixes the case where e.g. pwm-backlight can perfectly well be >>> set to >>> brightness 0 on boot in DT, which without this patch leads to the >>> display >>> brightness to be max instead of off. >>> >>> Fixes: c2adda27d202f ("video: backlight: Add of_find_backlight helper >>> in backlight.c") >>> Signed-off-by: Marek Vasut <marex@denx.de> >>> Cc: Daniel Thompson <daniel.thompson@linaro.org> >>> Cc: Meghana Madhyastha <meghana.madhyastha@gmail.com> >>> Cc: Noralf Trønnes <noralf@tronnes.org> >>> Cc: Sean Paul <seanpaul@chromium.org> >>> Cc: Thierry Reding <treding@nvidia.com> >> >> I have to admit that this patch really does makes it clear just how >> nasty the hack in of_find_backlight() currently is. >> >> Moreover I think it is also be obsolete. gpio-backlight power mode >> handling was pretty broken when this code was introduced. It was fixed >> in 2019 by ec665b756e6f ("backlight: gpio backlight: Correct initial >> power state handling") by trying to match the behaviour of PWM >> backlight. The new code always sets the brightness to 1 so I think we >> can just remove the hack from of_find_backlight() since I think it is >> unreachable. > > I assume by "new code" you mean the fixed gpio-backlight driver ? > > Dropping the whole code after the Note: is fine by me. I haven't actually tested it, but when I saw the patch that Daniel points to, it looked like this work around could be removed. I haven't got time to tests it, but I will ack a patch that removes the hack. Noralf.
diff --git a/drivers/video/backlight/backlight.c b/drivers/video/backlight/backlight.c index 537fe1b376ad7..dfb66171dec41 100644 --- a/drivers/video/backlight/backlight.c +++ b/drivers/video/backlight/backlight.c @@ -676,6 +676,7 @@ EXPORT_SYMBOL(of_find_backlight_by_node); static struct backlight_device *of_find_backlight(struct device *dev) { struct backlight_device *bd = NULL; + bool is_gpio_backlight = false; struct device_node *np; if (!dev) @@ -685,6 +686,8 @@ static struct backlight_device *of_find_backlight(struct device *dev) np = of_parse_phandle(dev->of_node, "backlight", 0); if (np) { bd = of_find_backlight_by_node(np); + is_gpio_backlight = + of_device_is_compatible(np, "gpio-backlight"); of_node_put(np); if (!bd) return ERR_PTR(-EPROBE_DEFER); @@ -692,7 +695,7 @@ static struct backlight_device *of_find_backlight(struct device *dev) * Note: gpio_backlight uses brightness as * power state during probe */ - if (!bd->props.brightness) + if (is_gpio_backlight && !bd->props.brightness) bd->props.brightness = bd->props.max_brightness; } }
The note in c2adda27d202f ("video: backlight: Add of_find_backlight helper in backlight.c") says that gpio-backlight uses brightness as power state. Other backlight drivers do not, so limit this workaround to gpio-backlight. This fixes the case where e.g. pwm-backlight can perfectly well be set to brightness 0 on boot in DT, which without this patch leads to the display brightness to be max instead of off. Fixes: c2adda27d202f ("video: backlight: Add of_find_backlight helper in backlight.c") Signed-off-by: Marek Vasut <marex@denx.de> Cc: Daniel Thompson <daniel.thompson@linaro.org> Cc: Meghana Madhyastha <meghana.madhyastha@gmail.com> Cc: Noralf Trønnes <noralf@tronnes.org> Cc: Sean Paul <seanpaul@chromium.org> Cc: Thierry Reding <treding@nvidia.com> --- drivers/video/backlight/backlight.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)