Re: [PATCH 09/10] drm/i915: enable RC6 workaround on Haswell

[Ben Widawsky <ben@bwidawsk.net>]

On Mon,  2 Jul 2012 11:51:10 -0300
Eugeni Dodonov <eugeni.dodonov@intel.com> wrote:

> For Haswell, on some of the early hardware revisions, it is possible to
> run into issues when RC6 state is enabled and when pipes change state.
> 
> v2: add comment saying that this is for early revisions only.
> 
> v3: beautify as suggested by Daniel Vetter.
> 
> Signed-off-by: Eugeni Dodonov <eugeni.dodonov@intel.com>
Acked-by: Ben Widawsky <ben@bwidawsk.net>
> ---
>  drivers/gpu/drm/i915/i915_reg.h |  5 +++++
>  drivers/gpu/drm/i915/intel_pm.c | 10 ++++++++++
>  2 files changed, 15 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
> index 9d5bf06..793a172 100644
> --- a/drivers/gpu/drm/i915/i915_reg.h
> +++ b/drivers/gpu/drm/i915/i915_reg.h
> @@ -4516,4 +4516,9 @@
>  #define  SFUSE_STRAP_DDIC_DETECTED	(1<<1)
>  #define  SFUSE_STRAP_DDID_DETECTED	(1<<0)
>  
> +#define WM_DBG				0x45280
> +#define  WM_DBG_DISALLOW_MULTIPLE_LP	(1<<0)
> +#define  WM_DBG_DISALLOW_MAXFIFO	(1<<1)
> +#define  WM_DBG_DISALLOW_SPRITE		(1<<2)
> +
>  #endif /* _I915_REG_H_ */
> diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
> index f54196f..604f9bf 100644
> --- a/drivers/gpu/drm/i915/intel_pm.c
> +++ b/drivers/gpu/drm/i915/intel_pm.c
> @@ -3465,6 +3465,16 @@ static void haswell_init_clock_gating(struct drm_device *dev)
>  	/* WaDisable4x2SubspanOptimization */
>  	I915_WRITE(CACHE_MODE_1,
>  		   _MASKED_BIT_ENABLE(PIXEL_SUBSPAN_COLLECT_OPT_DISABLE));
> +
> +	/* XXX: This is a workaround for early silicon revisions and should be
> +	 * removed later.
> +	 */
> +	I915_WRITE(WM_DBG,
> +			I915_READ(WM_DBG) |
> +			WM_DBG_DISALLOW_MULTIPLE_LP |
> +			WM_DBG_DISALLOW_SPRITE |
> +			WM_DBG_DISALLOW_MAXFIFO);
> +
>  }
>  
>  static void ivybridge_init_clock_gating(struct drm_device *dev)



-- 
Ben Widawsky, Intel Open Source Technology Center