| Message ID | 20170628111632.22582-1-enric.balletbo@collabora.com |
|---|---|
| State | Superseded |
| Headers | show |
On 28/06/17 12:16, Enric Balletbo i Serra wrote: > From: huang lin <hl@rock-chips.com> > > Add a pwm-delay-us property to specify the delay between setting an > initial (non-zero) PWM value and enabling the backlight, and also the > delay between disabling the backlight and setting PWM value to 0. > > Signed-off-by: huang lin <hl@rock-chips.com> > Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com> > --- > Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt b/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt > index 764db86..f75b08f 100644 > --- a/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt > +++ b/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt > @@ -17,6 +17,9 @@ Optional properties: > "pwms" property (see PWM binding[0]) > - enable-gpios: contains a single GPIO specifier for the GPIO which enables > and disables the backlight (see GPIO binding[1]) > + - pwm-delay-us: delay between setting an initial (non-zero) PWM value and > + enabling the backlight, and also the delay between disabling > + the backlight and setting PWM value to 0. If is safe to assume power-on delay and power-off delay will be the same? I've only took a quick look but several backlight controllers support asymetric power-on/off sequences... Daniel. > > [0]: Documentation/devicetree/bindings/pwm/pwm.txt > [1]: Documentation/devicetree/bindings/gpio/gpio.txt > @@ -32,4 +35,5 @@ Example: > > power-supply = <&vdd_bl_reg>; > enable-gpios = <&gpio 58 0>; > + pwm-delay-us = <10000>; > }; > -- To unsubscribe from this list: send the line "unsubscribe linux-pwm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Wed 2017-06-28 13:16:31, Enric Balletbo i Serra wrote: > From: huang lin <hl@rock-chips.com> > > Add a pwm-delay-us property to specify the delay between setting an > initial (non-zero) PWM value and enabling the backlight, and also the > delay between disabling the backlight and setting PWM value to 0. > Signed-off-by: huang lin <hl@rock-chips.com> > Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com> > --- > Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt b/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt > index 764db86..f75b08f 100644 > --- a/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt > +++ b/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt > @@ -17,6 +17,9 @@ Optional properties: > "pwms" property (see PWM binding[0]) > - enable-gpios: contains a single GPIO specifier for the GPIO which enables > and disables the backlight (see GPIO binding[1]) > + - pwm-delay-us: delay between setting an initial (non-zero) PWM value and > + enabling the backlight, and also the delay between disabling > + the backlight and setting PWM value to 0. > I understood it as "you set PWM and it takes a while for display to light up" but that's not correct. Changelog from second patch makes it clear. Please clarify it here, too. Pavel
Hi Daniel, Pavel, 2017-06-28 15:30 GMT+02:00 Pavel Machek <pavel@ucw.cz>: > On Wed 2017-06-28 13:16:31, Enric Balletbo i Serra wrote: >> From: huang lin <hl@rock-chips.com> >> >> Add a pwm-delay-us property to specify the delay between setting an >> initial (non-zero) PWM value and enabling the backlight, and also the >> delay between disabling the backlight and setting PWM value to 0. > > > >> Signed-off-by: huang lin <hl@rock-chips.com> >> Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com> >> --- >> Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt | 4 ++++ >> 1 file changed, 4 insertions(+) >> >> diff --git a/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt b/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt >> index 764db86..f75b08f 100644 >> --- a/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt >> +++ b/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt >> @@ -17,6 +17,9 @@ Optional properties: >> "pwms" property (see PWM binding[0]) >> - enable-gpios: contains a single GPIO specifier for the GPIO which enables >> and disables the backlight (see GPIO binding[1]) >> + - pwm-delay-us: delay between setting an initial (non-zero) PWM value and >> + enabling the backlight, and also the delay between disabling >> + the backlight and setting PWM value to 0. >> > >> If is safe to assume power-on delay and power-off delay will be the same? >> >> I've only took a quick look but several backlight controllers support asymetric power-on/off sequences.. Daniel, right the ones I checked are symmetric but asymmetric timings are possible I guess, so I think now that specify the two delays is more accurate, maybe the binding should be something like this? pwm-delay-us = <delay_before_on delay_after_off>; > I understood it as "you set PWM and it takes a while for display to > light up" > but that's not correct. Changelog from second patch makes it > clear. Please > clarify it here, too. Pavel, oh, your dude is interesting ... That's the idea, the sequence is: Power on, you set the PWM signal, wait a bit and set the LED_EN signal. Power off, you clear the LED_EN signal, wait a bit and stop the PWM signal. Note that the patch inverts the sequence, before this patch first you set LED_EN signal and then the PWM signal I assumed that the sequence was wrong but maybe I'm mistaken and there are some panels that follow the original sequence. On the few panels I checked the power on/off sequence is how I described above, i.e. see [1] p. 17, the sequence is first PWM and then LED_EN. I'll take a look at other panel datasheets, or if you know one, could you provide me the datasheet? Thanks, [1] http://www.jxlcd.com/Upload/PicFiles/N116BGE-L41.pdf > > Pavel > -- > (english) http://www.livejournal.com/~pavelmachek > (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html -- To unsubscribe from this list: send the line "unsubscribe linux-pwm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 28/06/17 15:15, Enric Balletbo Serra wrote: > Hi Daniel, Pavel, > > 2017-06-28 15:30 GMT+02:00 Pavel Machek <pavel@ucw.cz>: >> On Wed 2017-06-28 13:16:31, Enric Balletbo i Serra wrote: >>> From: huang lin <hl@rock-chips.com> >>> >>> Add a pwm-delay-us property to specify the delay between setting an >>> initial (non-zero) PWM value and enabling the backlight, and also the >>> delay between disabling the backlight and setting PWM value to 0. >> >> >> >>> Signed-off-by: huang lin <hl@rock-chips.com> >>> Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com> >>> --- >>> Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt | 4 ++++ >>> 1 file changed, 4 insertions(+) >>> >>> diff --git a/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt b/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt >>> index 764db86..f75b08f 100644 >>> --- a/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt >>> +++ b/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt >>> @@ -17,6 +17,9 @@ Optional properties: >>> "pwms" property (see PWM binding[0]) >>> - enable-gpios: contains a single GPIO specifier for the GPIO which enables >>> and disables the backlight (see GPIO binding[1]) >>> + - pwm-delay-us: delay between setting an initial (non-zero) PWM value and >>> + enabling the backlight, and also the delay between disabling >>> + the backlight and setting PWM value to 0. >>> >> >>> If is safe to assume power-on delay and power-off delay will be the same? >>> >>> I've only took a quick look but several backlight controllers support asymetric power-on/off sequences.. > > Daniel, right the ones I checked are symmetric but asymmetric timings > are possible I guess, so I think now that specify the two delays is > more accurate, maybe the binding should be something like this? > > pwm-delay-us = <delay_before_on delay_after_off>; I think so. Like you I can't actually point at any asymmetric power sequence diagrams but there are a controller devices with power sequencing registers that support asymmetry. I'm inclined to take that as a hint... >> I understood it as "you set PWM and it takes a while for display to >> light up" >> but that's not correct. Changelog from second patch makes it >> clear. Please >> clarify it here, too. > > Pavel, oh, your dude is interesting ... > > That's the idea, the sequence is: > Power on, you set the PWM signal, wait a bit and set the LED_EN signal. > Power off, you clear the LED_EN signal, wait a bit and stop the PWM signal. > > Note that the patch inverts the sequence, before this patch first you > set LED_EN signal and then the PWM signal > > I assumed that the sequence was wrong but maybe I'm mistaken and there > are some panels that follow the original sequence. On the few panels I > checked the power on/off sequence is how I described above, i.e. see > [1] p. 17, the sequence is first PWM and then LED_EN. I'll take a look > at other panel datasheets, or if you know one, could you provide me > the datasheet? > > Thanks, > > [1] http://www.jxlcd.com/Upload/PicFiles/N116BGE-L41.pdf > >> >> Pavel >> -- >> (english) http://www.livejournal.com/~pavelmachek >> (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html -- To unsubscribe from this list: send the line "unsubscribe linux-pwm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt b/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt index 764db86..f75b08f 100644 --- a/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt +++ b/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt @@ -17,6 +17,9 @@ Optional properties: "pwms" property (see PWM binding[0]) - enable-gpios: contains a single GPIO specifier for the GPIO which enables and disables the backlight (see GPIO binding[1]) + - pwm-delay-us: delay between setting an initial (non-zero) PWM value and + enabling the backlight, and also the delay between disabling + the backlight and setting PWM value to 0. [0]: Documentation/devicetree/bindings/pwm/pwm.txt [1]: Documentation/devicetree/bindings/gpio/gpio.txt @@ -32,4 +35,5 @@ Example: power-supply = <&vdd_bl_reg>; enable-gpios = <&gpio 58 0>; + pwm-delay-us = <10000>; };