Re: [PATCH v2 05/10] drm/i915/bdw: Remove WaDisableThreadStallDopClockGating

[Daniel Vetter <daniel@ffwll.ch>]

On Mon, Sep 28, 2015 at 10:51:39AM +0100, Arun Siluvery wrote:
> On 28/09/2015 09:44, Jani Nikula wrote:
> >On Fri, 25 Sep 2015, Arun Siluvery <arun.siluvery@linux.intel.com> wrote:
> >>Dropping it because it is for pre-production stepping.
> >
> >Hum, why have we added a pre-pro w/a without a stepping check... should
> >we backport this to stable kernels? What's the impact on production
> >hardware with vs. without the w/a?
> 
> The original patch that added pre-production comment is very old.
> 
> commit 101b376d358e2f724db5e0ac4d207079b16c4754
> Author: Rodrigo Vivi <rodrigo.vivi@intel.com>
> Date:   Thu Oct 9 07:11:47 2014 -0700
> 
>     drm/i915/bdw: Remove BDW preproduction W/As until C stepping.
> 
>     Let's clean this a bit
> 
>     v2: Rebase after other Mika's patch that removed some BDW production
> workarounds.
>     v3: Removed stepping info.

This commit also changed the wa right below by dropping the "May not be
needed for production.", but did not add a "(pre-production)" instead for
that case. And we're keeping that one. Would definitely be good to check
what's up with those two. I'll hold of merging this patch for now.
-Daniel

> 
> 
> For BDW it is only applicable UNTIL_D0. According to hsd it is related to a
> hang in emulation but I am checking with HW team to understand its impact
> (if any) better in production steppings.
> 
> regards
> Arun
> 
> >
> >BR,
> >Jani.
> >
> >
> >>
> >>Signed-off-by: Arun Siluvery <arun.siluvery@linux.intel.com>
> >>---
> >>  drivers/gpu/drm/i915/intel_ringbuffer.c | 3 ---
> >>  1 file changed, 3 deletions(-)
> >>
> >>diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
> >>index d8fa9d1..0b545cf 100644
> >>--- a/drivers/gpu/drm/i915/intel_ringbuffer.c
> >>+++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
> >>@@ -827,9 +827,6 @@ static int bdw_init_workarounds(struct intel_engine_cs *ring)
> >>  	if (ret)
> >>  		return ret;
> >>
> >>-	/* WaDisableThreadStallDopClockGating:bdw (pre-production) */
> >>-	WA_SET_BIT_MASKED(GEN8_ROW_CHICKEN, STALL_DOP_GATING_DISABLE);
> >>-
> >>  	/* WaDisableDopClockGating:bdw */
> >>  	WA_SET_BIT_MASKED(GEN7_ROW_CHICKEN2,
> >>  			  DOP_CLOCK_GATING_DISABLE);
> >>--
> >>1.9.1
> >>
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> >
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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