[Intel-gfx] [PATCH] drm/i915/vlv: assert and de-assert sideband reset at boot and resume v3

[Jesse Barnes]

On Wed, 21 May 2014 20:54:03 +0300
Ville Syrjälä <ville.syrjala at linux.intel.com> wrote:

> +	if (power_well_id == PUNIT_POWER_WELL_DPIO_CMN_BC && enable) 
> +		deassert cmnreset
>  }
> 
> 
> If those measures aren't enough, then I think this patch would be OK.
> But right now I have this nagging feeling that we may have shot
> ourselves in the foot and we're about to pile workarounds on top of our
> own bug.

I'll add these changes, with the additon that we need to do an actual
toggle at boot and init.  Simply asserting in suspend or gate and then
de-asserting isn't enough to re-calibrate, since we tried that on the
Chromebooks across suspend/resume and it wasn't enough to get things
going again after the chip had lost power.

Across simple power well transitions it ought to be enough though, and
that's easy enough to verify in testing.

-- 
Jesse Barnes, Intel Open Source Technology Center