Re: [PATCH] drm/i915/bdw: Disable idle DOP clock gating

Ville Syrjälä
2014-04-03T11:00:22Z

On Wed, Apr 02, 2014 at 07:46:37PM -0700, Ben Widawsky wrote:
> It seems we need this at least for the current platforms we have, but
> probably not later. In any event, it should cause too much harm as we do
> the same thing on several other platforms.
>
> Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
> ---
> drivers/gpu/drm/i915/intel_pm.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
> index fa00185..f73f8ca 100644
> --- a/drivers/gpu/drm/i915/intel_pm.c
> +++ b/drivers/gpu/drm/i915/intel_pm.c
> @@ -4868,6 +4868,10 @@ static void gen8_init_clock_gating(struct drm_device *dev)
> I915_WRITE(GEN7_HALF_SLICE_CHICKEN1,
> _MASKED_BIT_ENABLE(GEN7_SINGLE_SUBSCAN_DISPATCH_ENABLE));
>
> + /* WaDisableDopClockGating:bdw May not be needed for production */
> + I915_WRITE(GEN7_ROW_CHICKEN2,
> + _MASKED_BIT_ENABLE(DOP_CLOCK_GATING_DISABLE));

The hsd says you should also disable tcunit clock gating in
GEN6_UCGCTL1.

There's another w/a by the name of WaDisableRowChickenDopClockGating
which seems to be the same thing (apart from the tcunit bit maybe).
You might want to add that w/a note as well.

> +
> /* WaSwitchSolVfFArbitrationPriority:bdw */
> I915_WRITE(GAM_ECOCHK, I915_READ(GAM_ECOCHK) | HSW_ECOCHK_ARB_PRIO_SOL);
>
> --
> 1.9.1
>
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--
Ville Syrjälä
Intel OTC