linux-kernel - Re: [PATCH v6 13/13] video: backlight: mt6370: Add MediaTek MT6370 support

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Date:   Mon, 25 Jul 2022 11:07:35 +0200
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     ChiaEn Wu <peterwu.pub@...il.com>
Cc:     Lee Jones <lee.jones@...aro.org>,
        Daniel Thompson <daniel.thompson@...aro.org>,
        Jingoo Han <jingoohan1@...il.com>, Pavel Machek <pavel@....cz>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Sebastian Reichel <sre@...nel.org>,
        Chunfeng Yun <chunfeng.yun@...iatek.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jonathan Cameron <jic23@...nel.org>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>,
        Guenter Roeck <linux@...ck-us.net>,
        "Krogerus, Heikki" <heikki.krogerus@...ux.intel.com>,
        Helge Deller <deller@....de>,
        ChiaEn Wu <chiaen_wu@...htek.com>,
        Alice Chen <alice_chen@...htek.com>,
        cy_huang <cy_huang@...htek.com>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        Linux LED Subsystem <linux-leds@...r.kernel.org>,
        devicetree <devicetree@...r.kernel.org>,
        linux-arm Mailing List <linux-arm-kernel@...ts.infradead.org>,
        "moderated list:ARM/Mediatek SoC support" 
        <linux-mediatek@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        USB <linux-usb@...r.kernel.org>,
        linux-iio <linux-iio@...r.kernel.org>,
        "open list:FRAMEBUFFER LAYER" <linux-fbdev@...r.kernel.org>,
        szuni chen <szunichen@...il.com>
Subject: Re: [PATCH v6 13/13] video: backlight: mt6370: Add MediaTek MT6370 support

On Fri, Jul 22, 2022 at 12:25 PM ChiaEn Wu <peterwu.pub@...il.com> wrote:
>
> From: ChiaEn Wu <chiaen_wu@...htek.com>
>
> MediaTek MT6370 is a SubPMIC consisting of a single cell battery charger
> with ADC monitoring, RGB LEDs, dual channel flashlight, WLED backlight
> driver, display bias voltage supply, one general purpose LDO, and the
> USB Type-C & PD controller complies with the latest USB Type-C and PD
> standards.
>
> This adds support for MediaTek MT6370 Backlight driver. It's commonly used

Read Submitting Patches, please!

(In this case, find "This patch" in the above mentioned document, read
and act accordingly)

> to drive the display WLED. There are 4 channels inside, and each channel
> supports up to 30mA of current capability with 2048 current steps in
> exponential or linear mapping curves.

...

> +               brightness_val[1] = (brightness - 1) >> fls(MT6370_BL_DIM2_MASK);


(see below)

...

> +               /*
> +                * To make MT6372 using 14 bits to control the brightness
> +                * backward compatible with 11 bits brightness control
> +                * (like MT6370 and MT6371 do), we left shift the value
> +                * and pad with 1 to remaining bits. Hence, the MT6372's

to the remaining

> +                * backlight brightness will be almost the same as MT6370's
> +                * and MT6371's.
> +                */
> +               if (priv->vid_type == MT6370_VID_6372) {
> +                       brightness_val[0] <<= MT6370_BL_DIM2_6372_SHIFT;
> +                       brightness_val[0] |= MT6370_BL_DUMMY_6372_MASK;
> +               }

Nice! Why not...

...

> +       gpiod_set_value(priv->enable_gpio, brightness ? 1 : 0);

!!brightness will do as well.

...

> +       brightness = brightness_val[1] << fls(MT6370_BL_DIM2_MASK);

> +               val |= prop_val << (ffs(MT6370_BL_PWM_HYS_SEL_MASK) - 1);

> +               val |= ovp_uV << (ffs(MT6370_BL_OVP_SEL_MASK) - 1);

> +               val |= ocp_uA << (ffs(MT6370_BL_OC_SEL_MASK) - 1);

> +       val = prop_val << (ffs(MT6370_BL_CH_MASK) - 1);

...to use respective _SHIFTs in all these?

...

> +       priv->enable_gpio = devm_gpiod_get_optional(dev, "enable",
> +                                                   GPIOD_OUT_HIGH);
> +       if (IS_ERR(priv->enable_gpio))
> +               dev_err(dev, "Failed to get 'enable' gpio\n");

What does this mean? Shouldn't be

  return dev_err_probe()?

-- 
With Best Regards,
Andy Shevchenko