Re: [PATCH] drm/i915/gen9: Check for DC state mismatch

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

Patrik Jakobsson <patrik.jakobsson@linux.intel.com> writes:

> The DMC can incorrectly run off and allow DC states on it's own. We
> don't know the root-cause for this yet but this patch makes it more
> visible.
>
> Signed-off-by: Patrik Jakobsson <patrik.jakobsson@linux.intel.com>

Yes, we definitely need much more state checking and hardening
in this area.

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


> ---
>  drivers/gpu/drm/i915/i915_drv.h         | 1 +
>  drivers/gpu/drm/i915/intel_csr.c        | 2 ++
>  drivers/gpu/drm/i915/intel_runtime_pm.c | 8 ++++++++
>  3 files changed, 11 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index e11eef1..7e33454 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -746,6 +746,7 @@ struct intel_csr {
>  	uint32_t mmio_count;
>  	i915_reg_t mmioaddr[8];
>  	uint32_t mmiodata[8];
> +	uint32_t dc_state;
>  };
>  
>  #define DEV_INFO_FOR_EACH_FLAG(func, sep) \
> diff --git a/drivers/gpu/drm/i915/intel_csr.c b/drivers/gpu/drm/i915/intel_csr.c
> index 2a7ec31..b453fcc 100644
> --- a/drivers/gpu/drm/i915/intel_csr.c
> +++ b/drivers/gpu/drm/i915/intel_csr.c
> @@ -243,6 +243,8 @@ void intel_csr_load_program(struct drm_i915_private *dev_priv)
>  		I915_WRITE(dev_priv->csr.mmioaddr[i],
>  			   dev_priv->csr.mmiodata[i]);
>  	}
> +
> +	dev_priv->csr.dc_state = 0;
>  }
>  
>  static uint32_t *parse_csr_fw(struct drm_i915_private *dev_priv,
> diff --git a/drivers/gpu/drm/i915/intel_runtime_pm.c b/drivers/gpu/drm/i915/intel_runtime_pm.c
> index bbca527..e79674b 100644
> --- a/drivers/gpu/drm/i915/intel_runtime_pm.c
> +++ b/drivers/gpu/drm/i915/intel_runtime_pm.c
> @@ -494,10 +494,18 @@ static void gen9_set_dc_state(struct drm_i915_private *dev_priv, uint32_t state)
>  	val = I915_READ(DC_STATE_EN);
>  	DRM_DEBUG_KMS("Setting DC state from %02x to %02x\n",
>  		      val & mask, state);
> +
> +	/* Check if DMC is ignoring our DC state requests */
> +	if ((val & mask) != dev_priv->csr.dc_state)
> +		DRM_ERROR("DC state mismatch (0x%x -> 0x%x)\n",
> +			  dev_priv->csr.dc_state, val & mask);
> +
>  	val &= ~mask;
>  	val |= state;
>  	I915_WRITE(DC_STATE_EN, val);
>  	POSTING_READ(DC_STATE_EN);
> +
> +	dev_priv->csr.dc_state = val & mask;
>  }
>  
>  void bxt_enable_dc9(struct drm_i915_private *dev_priv)
> -- 
> 2.5.0
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