[PATCH v5 09/11] drm/tegra: Reset the SOR on probe

[Alexandre Courbot]

On Tue, Mar 3, 2015 at 12:46 AM, Simon Glass <sjg at chromium.org> wrote:
> Hi,
>
> On 2 March 2015 at 01:41, Alexandre Courbot <gnurou at gmail.com> wrote:
>>
>> On Thu, Feb 12, 2015 at 5:51 PM, Tomeu Vizoso
>> <tomeu.vizoso at collabora.com> wrote:
>> > As there isn't a way for the firmware on the Nyan chromebooks to hand
>> > over the display to the kernel.
>>
>> Could this have a side-effect on models for which the firmware *does*
>> hand over the display to the kernel? E.g. temporary glitch or black
>> screen?
>>
>> This is probably ok though, as such a handing over would need to be
>> documented in the firmware/kernel command line, and could thus be
>> caught to disable that code block if needed.
>
> Is there a general way in which this hand-over is done, e.g. with a
> device tree binding?

simple-framebuffer has bindings that describe a framebuffer handed
over by the firmware, and they look like the right way to describe
this. simplefb however is a framebuffer driver - a DRM driver would
need to seamlessly take over the display at some point and disable
simplefb. I don't know if this is possible at the moment.

Or maybe the DRM framework could look for a simple-framebuffer
compatible node, extract the framebuffer information, and pass it to
DRM drivers at probe time. That supposes a kernel in which
simple-framebuffer is not compiled in to prevent it from taking over
the display.