[Bug 108826] [GLK DSI] Black screen after grub - Ubuntu 18.04 - kernel latest tip 21.11.2018

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=108826

--- Comment #126 from Mark Wynn Garcia <markwynngarcia at outlook.com> ---
Stani. I think I know the problem. I'm still at work so I couldn't test it. 

I think it's because of the call to devm_gpiod_get_index() is only done once,
with the first call's value.

                gpio_desc = devm_gpiod_get_index(dev_priv->drm.dev,
                                                 NULL, gpio_index,
                                                 value ? GPIOD_OUT_LOW :
GPIOD_OUT_HIGH);

The look at gpiod_set_value() -> gpiod_set_value_nocheck()
(https://github.com/torvalds/linux/blob/master/drivers/gpio/gpiolib.c#L3335).
It flips the value if it's flagged as low. See also gpiod_configure_flags(). So
if it happens that the initial call sets the GPIOD_OUT_LOW flag, then every
subsequent calls will have the value flipped. So it can never set the GPIO to
1/true!

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