| Message ID | 1455755412-10495-1-git-send-email-aford173@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
* Adam Ford <aford173@gmail.com> [160217 16:30]: > The backlight pin is shared with Timer 10 PWM. This patch allows the > pwm_bl driver to enable the pwm run by this timer to dim the backlight. Nice to hear the PWM is now working! Are some of the pending fixes are still needed or is that all in Linux next now? Also one question below.. > @@ -194,6 +203,12 @@ > >; > }; > > + pwm_pins: pinmux_pwm_pins { > + pinctrl-single,pins = < > + OMAP3_CORE1_IOPAD(0x20B8, PIN_OUTPUT | PIN_OFF_OUTPUT_LOW | MUX_MODE3) /* gpmc_ncs5.gpt_10_pwm_evt */ > + >; > + }; > + > led_pins: pinmux_led_pins { > pinctrl-single,pins = < > OMAP3_CORE1_IOPAD(0x21d8, PIN_OUTPUT | MUX_MODE4) /* gpio_179 */ > @@ -220,7 +235,6 @@ > > backlight_pins: pinmux_backlight_pins { > pinctrl-single,pins = < > - OMAP3_CORE1_IOPAD(0x20B8, PIN_OUTPUT | PIN_OFF_OUTPUT_LOW | MUX_MODE4) /* gpmc_ncs5.gpio_56 */ > OMAP3_CORE1_IOPAD(0x2188, PIN_OUTPUT | PIN_OFF_OUTPUT_LOW | MUX_MODE4) /* mcbsp4_dx.gpio_154 */ > >; > }; What happens here if you don't set PIN_OFF_OUTPUT_LOW? Flickering on LCD or something? Regards, Tony -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
The PWM stuff worked with what was in linux-next. I didn't have to do any extra patches or anything. (Thanks to David Rivshin for helping me figure that out) PIN_OFF_OUTPUT_LOW was set to minimize power consumption during sleep. Looking at Logic PD's stock BSP, they have those pins enabled, and it seemed to help me cut power with "echo mem > /sys/power/state" If you would prefer that I not use that, I can certainly look at some other options. Just let me know, and I can adjust the patch accordingly. adam On Fri, Feb 19, 2016 at 12:43 PM, Tony Lindgren <tony@atomide.com> wrote: > * Adam Ford <aford173@gmail.com> [160217 16:30]: >> The backlight pin is shared with Timer 10 PWM. This patch allows the >> pwm_bl driver to enable the pwm run by this timer to dim the backlight. > > Nice to hear the PWM is now working! Are some of the pending > fixes are still needed or is that all in Linux next now? > > Also one question below.. > >> @@ -194,6 +203,12 @@ >> >; >> }; >> >> + pwm_pins: pinmux_pwm_pins { >> + pinctrl-single,pins = < >> + OMAP3_CORE1_IOPAD(0x20B8, PIN_OUTPUT | PIN_OFF_OUTPUT_LOW | MUX_MODE3) /* gpmc_ncs5.gpt_10_pwm_evt */ >> + >; >> + }; >> + >> led_pins: pinmux_led_pins { >> pinctrl-single,pins = < >> OMAP3_CORE1_IOPAD(0x21d8, PIN_OUTPUT | MUX_MODE4) /* gpio_179 */ >> @@ -220,7 +235,6 @@ >> >> backlight_pins: pinmux_backlight_pins { >> pinctrl-single,pins = < >> - OMAP3_CORE1_IOPAD(0x20B8, PIN_OUTPUT | PIN_OFF_OUTPUT_LOW | MUX_MODE4) /* gpmc_ncs5.gpio_56 */ >> OMAP3_CORE1_IOPAD(0x2188, PIN_OUTPUT | PIN_OFF_OUTPUT_LOW | MUX_MODE4) /* mcbsp4_dx.gpio_154 */ >> >; >> }; > > What happens here if you don't set PIN_OFF_OUTPUT_LOW? Flickering > on LCD or something? > > Regards, > > Tony -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
* Adam Ford <aford173@gmail.com> [160219 11:40]: > The PWM stuff worked with what was in linux-next. I didn't have to do > any extra patches or anything. (Thanks to David Rivshin for helping > me figure that out) OK nice. > PIN_OFF_OUTPUT_LOW was set to minimize power consumption during sleep. > Looking at Logic PD's stock BSP, they have those pins enabled, and it > seemed to help me cut power with "echo mem > /sys/power/state" OK makes sense to me thanks. > If you would prefer that I not use that, I can certainly look at some > other options. Just let me know, and I can adjust the patch > accordingly. No need to, there's other way to do it AFAIK :) Regards, Tony -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Wed, 17 Feb 2016 18:30:12 -0600 Adam Ford <aford173@gmail.com> wrote: > The backlight pin is shared with Timer 10 PWM. This patch allows the > pwm_bl driver to enable the pwm run by this timer to dim the backlight. > > Signed-off-by: Adam Ford <aford173@gmail.com> > --- [...] > bl: backlight { > - compatible = "gpio-backlight"; > + compatible = "pwm-backlight"; > pinctrl-names = "default"; > pinctrl-0 = <&backlight_pins>; > - > - gpios = <&gpio5 26 GPIO_ACTIVE_HIGH>, /* gpio_154 */ > - <&gpio2 24 GPIO_ACTIVE_HIGH>; /* gpio_56 */ > - default-on; > + pwms = <&pwm10 0 5000000 0>; > + brightness-levels = <0 10 20 30 40 50 60 70 80 90 100>; > + default-brightness-level = <7>; > + enable-gpios = <&gpio5 26 GPIO_ACTIVE_HIGH>; /* gpio_154 */ > }; [...] One thing to note: omap-dmtimer-pwm can't do a perfect 0 or 100% duty cycle. I think with the code in linux-next right now it will just configure the DMTIMER in a way that the TRM says is illegal, and with my [PATCH 2/4] it will set the lowest/highest possible duty-cycle (1-fclk cycle per period). Assuming you're using the 32768Hz fclk for timer10, that would mean the lowest effective duty cycle would be about 0.6%, and the highest 99.4%. If you're using a faster fclk, then the error would be proportionally less. Just wanted to mention that in case it's an issue for your backlight. FYI, I've seen other PWM drivers use a trick for the 0 and 100% cases where they actually force the largest possible period. This then dilutes the unwanted 1-cycle pulse as much as possible. I see no reason that couldn't be done for omap-dmtimer-pwm as well. Looking at the TRM, it may also be possible to turn off the trigger, and use the TCLR.SCPWM bit to force a perfect 0 or 100% duty cycle. -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
I did notice that 0 and 100 were not perfect, but it doesn't bother me because the visual effect was more important to me than precision. If you think it would be better, I could make the limits 1 and 99 for the extreme limits. adam On Fri, Feb 19, 2016 at 6:11 PM, David Rivshin (Allworx) <drivshin.allworx@gmail.com> wrote: > On Wed, 17 Feb 2016 18:30:12 -0600 > Adam Ford <aford173@gmail.com> wrote: > >> The backlight pin is shared with Timer 10 PWM. This patch allows the >> pwm_bl driver to enable the pwm run by this timer to dim the backlight. >> >> Signed-off-by: Adam Ford <aford173@gmail.com> >> --- > [...] >> bl: backlight { >> - compatible = "gpio-backlight"; >> + compatible = "pwm-backlight"; >> pinctrl-names = "default"; >> pinctrl-0 = <&backlight_pins>; >> - >> - gpios = <&gpio5 26 GPIO_ACTIVE_HIGH>, /* gpio_154 */ >> - <&gpio2 24 GPIO_ACTIVE_HIGH>; /* gpio_56 */ >> - default-on; >> + pwms = <&pwm10 0 5000000 0>; >> + brightness-levels = <0 10 20 30 40 50 60 70 80 90 100>; >> + default-brightness-level = <7>; >> + enable-gpios = <&gpio5 26 GPIO_ACTIVE_HIGH>; /* gpio_154 */ >> }; > [...] > > One thing to note: omap-dmtimer-pwm can't do a perfect 0 or 100% duty cycle. > I think with the code in linux-next right now it will just configure the > DMTIMER in a way that the TRM says is illegal, and with my [PATCH 2/4] it > will set the lowest/highest possible duty-cycle (1-fclk cycle per period). > Assuming you're using the 32768Hz fclk for timer10, that would mean the > lowest effective duty cycle would be about 0.6%, and the highest 99.4%. If > you're using a faster fclk, then the error would be proportionally less. > Just wanted to mention that in case it's an issue for your backlight. > > FYI, I've seen other PWM drivers use a trick for the 0 and 100% cases where > they actually force the largest possible period. This then dilutes the > unwanted 1-cycle pulse as much as possible. I see no reason that couldn't > be done for omap-dmtimer-pwm as well. > > Looking at the TRM, it may also be possible to turn off the trigger, and > use the TCLR.SCPWM bit to force a perfect 0 or 100% duty cycle. -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Fri, 19 Feb 2016 18:15:58 -0600 Adam Ford <aford173@gmail.com> wrote: > I did notice that 0 and 100 were not perfect, but it doesn't bother me > because the visual effect was more important to me than precision. If > you think it would be better, I could make the limits 1 and 99 for the > extreme limits. I think your devicetree itself is fine. If better behavior is required improving omap-dmtimer-pwm would probably be the right place to fix it. I think the hardware is capable if programmed in a special way, so we'd just need to check for those special-case values to handle differently. Also, If the pwm-backlight binding documentation is correct, the highest value will always ask for 100% duty cycle, so changing that to 99 wouldn't have an effect (and I doubt that anyone could discern 99.4% vs 100% anyways). I was more concerned with the low end, as I would be surprised if 0.6% brightness is noticeable. At least some LEDs are bright enough to be easily visible even at such low PWM. But if it's OK in your case, I wouldn't worry about it. > On Fri, Feb 19, 2016 at 6:11 PM, David Rivshin (Allworx) > <drivshin.allworx@gmail.com> wrote: > > On Wed, 17 Feb 2016 18:30:12 -0600 > > Adam Ford <aford173@gmail.com> wrote: > > > >> The backlight pin is shared with Timer 10 PWM. This patch allows the > >> pwm_bl driver to enable the pwm run by this timer to dim the backlight. > >> > >> Signed-off-by: Adam Ford <aford173@gmail.com> > >> --- > > [...] > >> bl: backlight { > >> - compatible = "gpio-backlight"; > >> + compatible = "pwm-backlight"; > >> pinctrl-names = "default"; > >> pinctrl-0 = <&backlight_pins>; > >> - > >> - gpios = <&gpio5 26 GPIO_ACTIVE_HIGH>, /* gpio_154 */ > >> - <&gpio2 24 GPIO_ACTIVE_HIGH>; /* gpio_56 */ > >> - default-on; > >> + pwms = <&pwm10 0 5000000 0>; > >> + brightness-levels = <0 10 20 30 40 50 60 70 80 90 100>; > >> + default-brightness-level = <7>; > >> + enable-gpios = <&gpio5 26 GPIO_ACTIVE_HIGH>; /* gpio_154 */ > >> }; > > [...] > > > > One thing to note: omap-dmtimer-pwm can't do a perfect 0 or 100% duty cycle. > > I think with the code in linux-next right now it will just configure the > > DMTIMER in a way that the TRM says is illegal, and with my [PATCH 2/4] it > > will set the lowest/highest possible duty-cycle (1-fclk cycle per period). > > Assuming you're using the 32768Hz fclk for timer10, that would mean the > > lowest effective duty cycle would be about 0.6%, and the highest 99.4%. If > > you're using a faster fclk, then the error would be proportionally less. > > Just wanted to mention that in case it's an issue for your backlight. > > > > FYI, I've seen other PWM drivers use a trick for the 0 and 100% cases where > > they actually force the largest possible period. This then dilutes the > > unwanted 1-cycle pulse as much as possible. I see no reason that couldn't > > be done for omap-dmtimer-pwm as well. > > > > Looking at the TRM, it may also be possible to turn off the trigger, and > > use the TCLR.SCPWM bit to force a perfect 0 or 100% duty cycle. -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
* Tony Lindgren <tony@atomide.com> [160219 11:50]: > * Adam Ford <aford173@gmail.com> [160219 11:40]: > > The PWM stuff worked with what was in linux-next. I didn't have to do > > any extra patches or anything. (Thanks to David Rivshin for helping > > me figure that out) > > OK nice. > > > PIN_OFF_OUTPUT_LOW was set to minimize power consumption during sleep. > > Looking at Logic PD's stock BSP, they have those pins enabled, and it > > seemed to help me cut power with "echo mem > /sys/power/state" > > OK makes sense to me thanks. > > > If you would prefer that I not use that, I can certainly look at some > > other options. Just let me know, and I can adjust the patch > > accordingly. > > No need to, there's other way to do it AFAIK :) Applying this into omap-for-v4.6/dts thanks. Tony -- To unsubscribe from this list: send the line "unsubscribe linux-omap" 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/arch/arm/boot/dts/logicpd-torpedo-37xx-devkit.dts b/arch/arm/boot/dts/logicpd-torpedo-37xx-devkit.dts index 4b00b58..1a97dda 100644 --- a/arch/arm/boot/dts/logicpd-torpedo-37xx-devkit.dts +++ b/arch/arm/boot/dts/logicpd-torpedo-37xx-devkit.dts @@ -71,6 +71,15 @@ linux,default-trigger = "none"; }; }; + + pwm10: dmtimer-pwm@10 { + compatible = "ti,omap-dmtimer-pwm"; + pinctrl-names = "default"; + pinctrl-0 = <&pwm_pins>; + ti,timers = <&timer10>; + #pwm-cells = <3>; + }; + }; &vaux1 { @@ -166,13 +175,13 @@ }; bl: backlight { - compatible = "gpio-backlight"; + compatible = "pwm-backlight"; pinctrl-names = "default"; pinctrl-0 = <&backlight_pins>; - - gpios = <&gpio5 26 GPIO_ACTIVE_HIGH>, /* gpio_154 */ - <&gpio2 24 GPIO_ACTIVE_HIGH>; /* gpio_56 */ - default-on; + pwms = <&pwm10 0 5000000 0>; + brightness-levels = <0 10 20 30 40 50 60 70 80 90 100>; + default-brightness-level = <7>; + enable-gpios = <&gpio5 26 GPIO_ACTIVE_HIGH>; /* gpio_154 */ }; }; @@ -194,6 +203,12 @@ >; }; + pwm_pins: pinmux_pwm_pins { + pinctrl-single,pins = < + OMAP3_CORE1_IOPAD(0x20B8, PIN_OUTPUT | PIN_OFF_OUTPUT_LOW | MUX_MODE3) /* gpmc_ncs5.gpt_10_pwm_evt */ + >; + }; + led_pins: pinmux_led_pins { pinctrl-single,pins = < OMAP3_CORE1_IOPAD(0x21d8, PIN_OUTPUT | MUX_MODE4) /* gpio_179 */ @@ -220,7 +235,6 @@ backlight_pins: pinmux_backlight_pins { pinctrl-single,pins = < - OMAP3_CORE1_IOPAD(0x20B8, PIN_OUTPUT | PIN_OFF_OUTPUT_LOW | MUX_MODE4) /* gpmc_ncs5.gpio_56 */ OMAP3_CORE1_IOPAD(0x2188, PIN_OUTPUT | PIN_OFF_OUTPUT_LOW | MUX_MODE4) /* mcbsp4_dx.gpio_154 */ >; };
The backlight pin is shared with Timer 10 PWM. This patch allows the pwm_bl driver to enable the pwm run by this timer to dim the backlight. Signed-off-by: Adam Ford <aford173@gmail.com> --- arch/arm/boot/dts/logicpd-torpedo-37xx-devkit.dts | 26 +++++++++++++++++------ 1 file changed, 20 insertions(+), 6 deletions(-)