lkml.org 
[lkml]   [2020]   [May]   [11]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH v5 1/6] drm/bridge: ti-sn65dsi86: Export bridge GPIOs to Linux
From
Date
Quoting Douglas Anderson (2020-05-07 14:34:55)
> The ti-sn65dsi86 MIPI DSI to eDP bridge chip has 4 pins on it that can
> be used as GPIOs in a system. Each pin can be configured as input,
> output, or a special function for the bridge chip. These are:
> - GPIO1: SUSPEND Input
> - GPIO2: DSIA VSYNC
> - GPIO3: DSIA HSYNC or VSYNC
> - GPIO4: PWM
>
> Let's expose these pins as GPIOs. A few notes:
> - Access to ti-sn65dsi86 is via i2c so we set "can_sleep".
> - These pins can't be configured for IRQ.
> - There are no programmable pulls or other fancy features.
> - Keeping the bridge chip powered might be expensive. The driver is
> setup such that if all used GPIOs are only inputs we'll power the
> bridge chip on just long enough to read the GPIO and then power it
> off again. Setting a GPIO as output will keep the bridge powered.
> - If someone releases a GPIO we'll implicitly switch it to an input so
> we no longer need to keep the bridge powered for it.
>
> Because of all of the above limitations we just need to implement a
> bare-bones GPIO driver. The device tree bindings already account for
> this device being a GPIO controller so we only need the driver changes
> for it.
>
> NOTE: Despite the fact that these pins are nominally muxable I don't
> believe it makes sense to expose them through the pinctrl interface as
> well as the GPIO interface. The special functions are things that the
> bridge chip driver itself would care about and it can just configure
> the pins as needed.
>
> Signed-off-by: Douglas Anderson <dianders@chromium.org>
> Cc: Linus Walleij <linus.walleij@linaro.org>
> Cc: Bartosz Golaszewski <bgolaszewski@baylibre.com>
> ---

Reviewed-by: Stephen Boyd <swboyd@chromium.org>

\
 
 \ /
  Last update: 2020-05-11 18:24    [W:0.154 / U:0.196 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site