[PATCH 01/17] drm/tegra: dc: Add powergate support

[Thierry Reding]

On Mon, Nov 03, 2014 at 12:15:38PM -0500, Sean Paul wrote:
> On Mon, Nov 3, 2014 at 4:27 AM, Thierry Reding <thierry.reding at gmail.com> wrote:
> > From: Thierry Reding <treding at nvidia.com>
> >
> > Both display controllers are in their own power partition. Currently the
> > driver relies on the assumption that these partitions are on (which is
> > the hardware default). However some bootloaders may disable them, so the
> > driver must make sure to turn them back on to avoid hangs.
> >
> 
> A bug in our firmware caused the host1x block to be in a bad state on
> boot such that we had to pulse the reset control in kernel probe to
> recover. I'm not sure how paranoid you want to be here, but something
> to keep in mind.

I think I'd rather not do that. The reason is simple: eventually what
I'd like to do is implement a way for firmware to hand over display to
the kernel so we can seamlessly transition graphics. If we pulse reset
for any of the blocks we can no longer do that.

Thierry
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