[Intel-gfx] [PATCH 2/5] drm/i915: Do not read GAMMA_MODE register

[Matt Roper]

On Tue, Feb 23, 2016 at 10:36:36AM +0000, Lionel Landwerlin wrote:
> On 23/02/16 00:38, Matt Roper wrote:
> >On Mon, Feb 22, 2016 at 02:18:08PM +0000, Lionel Landwerlin wrote:
> >>Implement Daniel Stone's recommendation to not read registers to infer
> >>the hardware's state.
> >>
> >>Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin at intel.com>
> >Do we need to ensure that software and hardware state are synchronized
> >at startup?  A boot firmware might have set it to something different
> >before our driver starts up; if we use 'fastboot' then we might not do
> >any modesets and might wind up with 0 (8BIT) in our state variable, but
> >something else actually programmed into the hardware.
> >
> >
> >Matt
> 
> Thanks Matt,
> 
> It makes sense know, I couldn't understand why this would ever be at
> something different that 8bit mode...
> I guess the value should be read from the intel_color_init()
> function upon startup.

We have a hardware state readout where we reconstruct the hardware state
for various things like plane state and such; you could add color
management readout to that.  Alternatively, we could just force
known-good values into the hardware at startup as we do (or will very
soon) for stuff we don't trust the BIOS to get right like watermarks.


Matt

> 
> -
> Lionel

-- 
Matt Roper
Graphics Software Engineer
IoTG Platform Enabling & Development
Intel Corporation
(916) 356-2795