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@xxxxxxxxxxxx> > Cc: Linus Walleij <linus.walleij@xxxxxxxxxx> > Cc: Bartosz Golaszewski <bgolaszewski@xxxxxxxxxxxx> > --- Reviewed-by: Stephen Boyd <swboyd@xxxxxxxxxxxx>
