linux-kernel - Re: [PATCH] backlight: add led-backlight driver

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Message-ID: <20200219234437.l6ac7usebu7rnzsy@earth.universe>
Date:   Thu, 20 Feb 2020 00:44:37 +0100
From:   Sebastian Reichel <sre@...nel.org>
To:     Tony Lindgren <tony@...mide.com>
Cc:     Pavel Machek <pavel@....cz>, Lee Jones <lee.jones@...aro.org>,
        kernel list <linux-kernel@...r.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        linux-omap@...r.kernel.org, nekit1000@...il.com, mpartap@....net,
        merlijn@...zup.org, martin_rysavy@...trum.cz, agx@...xcpu.org,
        daniel.thompson@...aro.org, jingoohan1@...il.com,
        dri-devel@...ts.freedesktop.org, tomi.valkeinen@...com,
        jjhiblot@...com
Subject: Re: [PATCH] backlight: add led-backlight driver

On Wed, Feb 19, 2020 at 11:45:40AM -0800, Tony Lindgren wrote:
> * Pavel Machek <pavel@....cz> [200219 19:15]:
> > From: Tomi Valkeinen <tomi.valkeinen@...com>
> > 
> > This patch adds a led-backlight driver (led_bl), which is similar to
> > pwm_bl except the driver uses a LED class driver to adjust the
> > brightness in the HW. Multiple LEDs can be used for a single backlight.
> > 
> > Signed-off-by: Tomi Valkeinen <tomi.valkeinen@...com>
> > Signed-off-by: Jean-Jacques Hiblot <jjhiblot@...com>
> > Acked-by: Pavel Machek <pavel@....cz>
> > Reviewed-by: Daniel Thompson <daniel.thompson@...aro.org>
> > Acked-by: Lee Jones <lee.jones@...aro.org>
> > Acked-by: Tony Lindgren <tony@...mide.com>
> > Tested-by: Tony Lindgren <tony@...mide.com>
> > Signed-off-by: Pavel Machek <pavel@....cz>
> > ---
> >  drivers/video/backlight/Kconfig  |   7 ++
> >  drivers/video/backlight/Makefile |   1 +
> >  drivers/video/backlight/led_bl.c | 260 +++++++++++++++++++++++++++++++++++++++
> >  3 files changed, 268 insertions(+)
> >  create mode 100644 drivers/video/backlight/led_bl.c
> > 
> > Hi!
> > 
> > Here's the version of the driver I have. AFAICT
> > default-brightness-level handling is ok, so does not need to be
> > changed.
> > 
> > Lee, it would be easiest for me if you could apply it to your tree and
> > push, but given enough time I can push it to Linus, too.
> 
> Oh you're using quoted-printable for patches.. Got it applied now,
> and it still works. Below is also the related dts change that
> I tested with.
> 
> Feel free to pick the dts change too, naturally that should
> not be applied before the driver.
> 
> If you guys instead want me to pick these both into my fixes
> branch, just let me know and I'll do the explaining why these
> are needed as fixes. Basically we no longer have a way to enable
> the LCD backlight for droid4 manually starting with v5.6-rc1
> unlike earlier.
> 
> Regards,
> 
> Tony
> 
> 8< ------------------
> From tony Mon Sep 17 00:00:00 2001
> From: Tony Lindgren <tony@...mide.com>
> Date: Wed, 19 Feb 2020 11:25:27 -0800
> Subject: [PATCH] ARM: dts: droid4: Configure LED backlight for lm3532
> 
> With the LED backlight changes merged, we still need the dts configured
> to have backlight working for droid4. Based on an earlier patch from
> Pavel Machek <pavel@....cz>, let's configure the backlight but update
> the value range to be more usable.
> 
> We have a range of 256 register values split into 8 steps, so we can
> generate the brightness levels backwards with:
> 
> $ for i in 0 1 2 3 4 5 6 7; do echo "255 - ${i} * (256 / 8)" | bc; done
> 
> To avoid more confusion why the LCD backlight is still not on, let's
> also enable LED backlight as a loadable module for omap2plus_defconfig.
> 
> Cc: Merlijn Wajer <merlijn@...zup.org>
> Cc: Pavel Machek <pavel@....cz>
> Signed-off-by: Tony Lindgren <tony@...mide.com>
> ---
>  arch/arm/boot/dts/motorola-mapphone-common.dtsi | 13 +++++++++++--
>  arch/arm/configs/omap2plus_defconfig            |  1 +
>  2 files changed, 12 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/arm/boot/dts/motorola-mapphone-common.dtsi b/arch/arm/boot/dts/motorola-mapphone-common.dtsi
> --- a/arch/arm/boot/dts/motorola-mapphone-common.dtsi
> +++ b/arch/arm/boot/dts/motorola-mapphone-common.dtsi
> @@ -182,6 +182,14 @@ vibrator {
>  		pwm-names = "enable", "direction";
>  		direction-duty-cycle-ns = <10000000>;
>  	};
> +
> +	backlight: backlight {
> +		compatible = "led-backlight";
> +
> +		leds = <&backlight_led>;
> +		brightness-levels = <31 63 95 127 159 191 223 255>;
> +		default-brightness-level = <6>;
> +	};
>  };
>  
>  &dss {
> @@ -205,6 +213,8 @@ lcd0: display {
>  		vddi-supply = <&lcd_regulator>;
>  		reset-gpios = <&gpio4 5 GPIO_ACTIVE_HIGH>;	/* gpio101 */
>  
> +		backlight = <&backlight>;
> +
>  		width-mm = <50>;
>  		height-mm = <89>;
>  
> @@ -393,12 +403,11 @@ led-controller@38 {
>  		ramp-up-us = <1024>;
>  		ramp-down-us = <8193>;
>  
> -		led@0 {
> +		backlight_led: led@0 {
>  			reg = <0>;
>  			led-sources = <2>;
>  			ti,led-mode = <0>;
>  			label = ":backlight";
> -			linux,default-trigger = "backlight";
>  		};
>  
>  		led@1 {
> diff --git a/arch/arm/configs/omap2plus_defconfig b/arch/arm/configs/omap2plus_defconfig
> --- a/arch/arm/configs/omap2plus_defconfig
> +++ b/arch/arm/configs/omap2plus_defconfig
> @@ -375,6 +375,7 @@ CONFIG_BACKLIGHT_GENERIC=m
>  CONFIG_BACKLIGHT_PWM=m
>  CONFIG_BACKLIGHT_PANDORA=m
>  CONFIG_BACKLIGHT_GPIO=m
> +CONFIG_BACKLIGHT_LED=m
>  CONFIG_FRAMEBUFFER_CONSOLE=y
>  CONFIG_FRAMEBUFFER_CONSOLE_ROTATION=y
>  CONFIG_LOGO=y

Finally :)

Reviewed-by: Sebastian Reichel <sebastian.reichel@...labora.com>

-- Sebastian

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