mi0283qt driver issues

[Tom Callaway]

On 04/18/2018 06:22 AM, Noralf Trønnes wrote:
> It turns out that the reason for this is that the pitft has a hw reset
> circuit that resets only on power-on and not on each reboot through a
> gpio like rpi-display does.
> 
> When the driver is enabling the display pipeline it checks if the
> controller is already initialized, and skips setup if it is. This means
> that the rotation value is only applied after power-on on the pitft and
> not on each reboot.
> 
> Turning off the "display" before rebooting should also work:
> 
> $ # change rotation value
> $ echo "28" | sudo tee /sys/kernel/debug/dri/0/command
> $ sudo reboot
> 
> Rotation/mirror/flip/bgr is controlled by commmand 0x36. The current
> value is returned by command 0x0b:
> 
> $ sudo cat /sys/kernel/debug/dri/0/command | grep "0b:"
> 0b: f8
> 
> So to fix this in the driver the rotation value has to always be applied
> regardless of display "on" state. This can be done by moving the rotation
> code in mi0283qt_enable() down after the out: label.

Confirmed, turning off the display before rebooting works, thanks.

To fix this correctly, it seems like there are two paths:

* If it is always safe to apply the rotation value regardless of display
state, move the rotation code down after out: in the mi0283qt driver.

* If this fix is only safe on the pitft (and not on the other panels
driven by the mi0283qt driver), either conditionalizing this behavior
somehow, or making a separate ili9340 driver with this change.

I'm willing to make patches if necessary here, but it is not clear which
path is the correct one.

~tom