Re: [PATCH v2 27/27] drm/tegra: Add Tegra114 gr2d support

["Terje Bergström" <tbergstrom-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>]

On 16.10.2013 11:48, Thierry Reding wrote:
> On Tue, Oct 15, 2013 at 09:19:18AM -0600, Stephen Warren wrote:
>> Taking advantage of new functionality isn't the issue. The issue is
>> whether a driver that was written purely to the spec of Tegra20 can
>> successfully operate on the HW. If it can't, then the HW is not
>> compatible with Tegra20. Terje's previous comments sounded like the HW
>> is not backwards-compatible, although his more recent comments make it
>> sound like only SW policy differences, which shouldn't be part of DT
>> anyway.
> 
> Well, as good as I can tell it is backwards-compatible. I've been
> testing the code included in this series with the same simple test
> program that clears a rectangle on Tegra20, Tegra30 and Tegra114.
> 
> Furthermore our internal register specification files are identical,
> with the exception of some whitespace changes for all three generations.
> I think that qualifies as backwards-compatible?

A driver written for Tegra20 2D works with Tegra114 2D. Not necessarily
vice versa, because Tegra114's driver can ask for higher clocks, or it
might want to power gate 2D.

I mentioned earlier bringup activities. Perhaps Stephen took that in a
way I didn't intend.

Terje