Re: [PATCH] drm/i915/vlv: reset VLV media force wake request register

[Mika Kuoppala <mika.kuoppala@linux.intel.com>]

Jani Nikula <jani.nikula@intel.com> writes:

> Media force wake get hangs the machine when the system is booted without
> displays attached. The assumption is that (at least some versions of)
> the firmware has skipped some initialization in that case.
>
> Empirical evidence suggests we need to reset the media force wake
> request register in addition to the render one to avoid hangs.
>
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=75895
> Reported-by: Imre Deak <imre.deak@intel.com>
> Reported-by: Darren Hart <dvhart@linux.intel.com>
> Cc: stable@vger.kernel.org
> Signed-off-by: Jani Nikula <jani.nikula@intel.com>

Reviewed-by: Mika Kuoppala <mika.kuoppala@intel.com>

> ---
>
> Darren, a Tested-by would be much appreciated!
>
> Thanks,
> Jani.
> ---
>  drivers/gpu/drm/i915/intel_uncore.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/intel_uncore.c b/drivers/gpu/drm/i915/intel_uncore.c
> index 76dc185793ce..27fe2df47d73 100644
> --- a/drivers/gpu/drm/i915/intel_uncore.c
> +++ b/drivers/gpu/drm/i915/intel_uncore.c
> @@ -185,6 +185,8 @@ static void vlv_force_wake_reset(struct drm_i915_private *dev_priv)
>  {
>  	__raw_i915_write32(dev_priv, FORCEWAKE_VLV,
>  			   _MASKED_BIT_DISABLE(0xffff));
> +	__raw_i915_write32(dev_priv, FORCEWAKE_MEDIA_VLV,
> +			   _MASKED_BIT_DISABLE(0xffff));
>  	/* something from same cacheline, but !FORCEWAKE_VLV */
>  	__raw_posting_read(dev_priv, FORCEWAKE_ACK_VLV);
>  }
> -- 
> 1.9.1
>
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