Re: [PATCH 1/4] drm/i915/bxt: limit WaDisableMaskBasedCammingInRCC to stepping A

[Damien Lespiau <damien.lespiau@intel.com>]

On Tue, May 19, 2015 at 03:04:59PM +0300, Imre Deak wrote:
> Also make the WA comment consistent with the rest, where the stepping
> info is not shown.
> 
> Signed-off-by: Imre Deak <imre.deak@intel.com>
> ---
>  drivers/gpu/drm/i915/intel_ringbuffer.c | 9 +++------
>  1 file changed, 3 insertions(+), 6 deletions(-)
> 
> [ The patchset is a follow-up to:
>   http://lists.freedesktop.org/archives/intel-gfx/2015-May/065989.html ]
> 
> diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
> index 9b96ed7..461b9be 100644
> --- a/drivers/gpu/drm/i915/intel_ringbuffer.c
> +++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
> @@ -961,12 +961,9 @@ static int gen9_init_workarounds(struct intel_engine_cs *ring)
>  	WA_CLR_BIT_MASKED(GEN9_HALF_SLICE_CHICKEN5,
>  			  GEN9_CCS_TLB_PREFETCH_ENABLE);
>  
> -	/*
> -	 * FIXME: don't apply the following on BXT for stepping C. On BXT A0
> -	 * the flag reads back as 0.
> -	 */
> -	/* WaDisableMaskBasedCammingInRCC:sklC,bxtA */
> -	if (INTEL_REVID(dev) == SKL_REVID_C0 || IS_BROXTON(dev))
> +	/* WaDisableMaskBasedCammingInRCC:skl,bxt */

For the record, there seem to be some confusion in the W/A db:

  - The W/A seems to have been renamed to WaDisablePixelMaskBasedCammingInRcpbe
    and indeed there's a bit to do that, but the bug in question talks
    about bit 14 of 7308, which is the disabling bit for the RCC unit
  - The W/A isn't listed in the W/A db for BXT

In doubt, defaulting to trusting the spec and bug db is probably the
saner option, so:

Reviewed-by: Damien Lespiau <damien.lespiau@intel.com>

-- 
Damien

> +	if ((IS_SKYLAKE(dev) && INTEL_REVID(dev) == SKL_REVID_C0) ||
> +	    (IS_BROXTON(dev) && INTEL_REVID(dev) < BXT_REVID_B0))
>  		WA_SET_BIT_MASKED(SLICE_ECO_CHICKEN0,
>  				  PIXEL_MASK_CAMMING_DISABLE);
>  
> -- 
> 2.1.4
> 
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