linux-kernel - Re: [PATCH 5/5] drm/i915/dsi: Control panel and backlight enable GPIOs on BYT

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Date:   Mon, 16 Dec 2019 11:29:54 +0100
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Hans de Goede <hdegoede@...hat.com>
Cc:     Jani Nikula <jani.nikula@...ux.intel.com>,
        Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        Ville Syrjälä <ville.syrjala@...ux.intel.com>,
        Lee Jones <lee.jones@...aro.org>,
        intel-gfx <intel-gfx@...ts.freedesktop.org>,
        "open list:DRM PANEL DRIVERS" <dri-devel@...ts.freedesktop.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>
Subject: Re: [PATCH 5/5] drm/i915/dsi: Control panel and backlight enable
 GPIOs on BYT

On Sun, Dec 15, 2019 at 5:38 PM Hans de Goede <hdegoede@...hat.com> wrote:

> On Bay Trail devices the MIPI power on/off sequences for DSI LCD panels
> do not control the LCD panel- and backlight-enable GPIOs. So far, when
> the VBT indicates we should use the SoC for backlight control, we have
> been relying on these GPIOs being configured as output and driven high by
> the Video BIOS (GOP) when it initializes the panel.
>
> This does not work when the device is booted with a HDMI monitor connected
> as then the GOP will initialize the HDMI instead of the panel, leaving the
> panel black, even though the i915 driver tries to output an image to it.
>
> Likewise on some device-models when the GOP does not initialize the DSI
> panel it also leaves the mux of the PWM0 pin in generic GPIO mode instead
> of muxing it to the PWM controller.
>
> This commit makes the DSI code control the SoC GPIOs for panel- and
> backlight-enable on BYT, when the VBT indicates the SoC should be used
>
> for backlight control. It also ensures that the PWM0 pin is muxed to the
> PWM controller in this case.
>
> This fixes the LCD panel not lighting up on various devices when booted
> with a HDMI monitor connected. This has been tested to fix this on the
> following devices:
>
> Peaq C1010
> Point of View MOBII TAB-P800W
> Point of View MOBII TAB-P1005W
> Terra Pad 1061
> Yours Y8W81
>
> Signed-off-by: Hans de Goede <hdegoede@...hat.com>

Looks good to me:
Reviewed-by: Linus Walleij <linus.walleij@...aro.org>

Yours,
Linus Walleij