[Intel-gfx] [PATCH 1/4] drm/i915/bdw: Add missing delay during L3 SQC credit programming

[Ville Syrjälä]

On Mon, Apr 25, 2016 at 03:38:05PM +0300, Imre Deak wrote:
> BSpec requires us to wait ~100 clocks before re-enabling clock gating,
> so make sure we do this.
> 
> Signed-off-by: Imre Deak <imre.deak at intel.com>

Reviewed-by: Ville Syrjälä <ville.syrjala at linux.intel.com>

> ---
>  drivers/gpu/drm/i915/intel_pm.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
> index 702f683..a6fd4dd 100644
> --- a/drivers/gpu/drm/i915/intel_pm.c
> +++ b/drivers/gpu/drm/i915/intel_pm.c
> @@ -6711,6 +6711,12 @@ static void broadwell_init_clock_gating(struct drm_device *dev)
>  	misccpctl = I915_READ(GEN7_MISCCPCTL);
>  	I915_WRITE(GEN7_MISCCPCTL, misccpctl & ~GEN7_DOP_CLOCK_GATE_ENABLE);
>  	I915_WRITE(GEN8_L3SQCREG1, BDW_WA_L3SQCREG1_DEFAULT);
> +	/*
> +	 * Wait at least 100 clocks before re-enabling clock gating. See
> +	 * the definition of L3SQCREG1 in BSpec.
> +	 */
> +	POSTING_READ(GEN8_L3SQCREG1);
> +	udelay(1);
>  	I915_WRITE(GEN7_MISCCPCTL, misccpctl);
>  
>  	/*
> -- 
> 2.5.0
> 
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-- 
Ville Syrjälä
Intel OTC