[PATCH] drm/i915: Correct MI_STORE_DWORD_INDEX usage

[PATCH] drm/i915: Correct MI_STORE_DWORD_INDEX usage

[Ben Widawsky]

This has been incorrect since the original commit from Oscar Mateo here:
commit 4da46e1e5bb7e7396fad172cdaffbe496562f3d8
Author: Oscar Mateo <oscar.mateo@intel.com>
Date:   Thu Jul 24 17:04:27 2014 +0100

    drm/i915/bdw: GEN-specific logical ring emit request

The command's offset field is only 10 bits, and this is correct in all the other
add_request commands. It's highly likely this this patch makes no functional
difference because the hardware will hopefully ignore 31:12 anyway. Technically
the existing code is wrong because the docs say the upper bits are MBZ.
Ultimately, the patch just clears up the confusion.

NOTE: This patch was compile tested only.
NOTE2: The modern docs call it MI_STORE_DATA_INDEX not MI_STORE_DWORD_INDEX

Cc: Oscar Mateo <oscar.mateo@intel.com>
Cc: Damien Lespiau <damien.lespiau@intel.com>
Signed-off-by: Ben Widawsky <benjamin.widawsky@intel.com>
---
 drivers/gpu/drm/i915/intel_lrc.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
index 3aa6147..90d4dbb 100644
--- a/drivers/gpu/drm/i915/intel_lrc.c
+++ b/drivers/gpu/drm/i915/intel_lrc.c
@@ -1793,7 +1793,6 @@ static void bxt_a_set_seqno(struct intel_engine_cs *ring, u32 seqno)
 static int gen8_emit_request(struct drm_i915_gem_request *request)
 {
 	struct intel_ringbuffer *ringbuf = request->ringbuf;
-	struct intel_engine_cs *ring = ringbuf->ring;
 	u32 cmd;
 	int ret;
 
@@ -1811,8 +1810,7 @@ static int gen8_emit_request(struct drm_i915_gem_request *request)
 
 	intel_logical_ring_emit(ringbuf, cmd);
 	intel_logical_ring_emit(ringbuf,
-				(ring->status_page.gfx_addr +
-				(I915_GEM_HWS_INDEX << MI_STORE_DWORD_INDEX_SHIFT)));
+				I915_GEM_HWS_INDEX << MI_STORE_DWORD_INDEX_SHIFT);
 	intel_logical_ring_emit(ringbuf, 0);
 	intel_logical_ring_emit(ringbuf, i915_gem_request_get_seqno(request));
 	intel_logical_ring_emit(ringbuf, MI_USER_INTERRUPT);
-- 
2.6.4

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Re: [PATCH] drm/i915: Correct MI_STORE_DWORD_INDEX usage

[Chris Wilson]

On Tue, Dec 15, 2015 at 04:13:49PM -0800, Ben Widawsky wrote:
> This has been incorrect since the original commit from Oscar Mateo here:
> commit 4da46e1e5bb7e7396fad172cdaffbe496562f3d8
> Author: Oscar Mateo <oscar.mateo@intel.com>
> Date:   Thu Jul 24 17:04:27 2014 +0100
> 
>     drm/i915/bdw: GEN-specific logical ring emit request
> 
> The command's offset field is only 10 bits, and this is correct in all the other
> add_request commands. It's highly likely this this patch makes no functional
> difference because the hardware will hopefully ignore 31:12 anyway. Technically
> the existing code is wrong because the docs say the upper bits are MBZ.
> Ultimately, the patch just clears up the confusion.
> 
> NOTE: This patch was compile tested only.
> NOTE2: The modern docs call it MI_STORE_DATA_INDEX not MI_STORE_DWORD_INDEX

It doesn't use MI_STORE_DATA_INDEX, but a write to a specific memory
address (MI_STORE_DWORD_IMM) as it is not storing in the per-context HWS
but a global (per-engine) page.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre
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Re: [PATCH] drm/i915: Correct MI_STORE_DWORD_INDEX usage

[Ben Widawsky]

On Wed, Dec 16, 2015 at 12:18:20AM +0000, Chris Wilson wrote:
> On Tue, Dec 15, 2015 at 04:13:49PM -0800, Ben Widawsky wrote:
> > This has been incorrect since the original commit from Oscar Mateo here:
> > commit 4da46e1e5bb7e7396fad172cdaffbe496562f3d8
> > Author: Oscar Mateo <oscar.mateo@intel.com>
> > Date:   Thu Jul 24 17:04:27 2014 +0100
> > 
> >     drm/i915/bdw: GEN-specific logical ring emit request
> > 
> > The command's offset field is only 10 bits, and this is correct in all the other
> > add_request commands. It's highly likely this this patch makes no functional
> > difference because the hardware will hopefully ignore 31:12 anyway. Technically
> > the existing code is wrong because the docs say the upper bits are MBZ.
> > Ultimately, the patch just clears up the confusion.
> > 
> > NOTE: This patch was compile tested only.
> > NOTE2: The modern docs call it MI_STORE_DATA_INDEX not MI_STORE_DWORD_INDEX
> 
> It doesn't use MI_STORE_DATA_INDEX, but a write to a specific memory
> address (MI_STORE_DWORD_IMM) as it is not storing in the per-context HWS
> but a global (per-engine) page.
> -Chris
> 
> -- 
> Chris Wilson, Intel Open Source Technology Centre

You're right. I just noticed the cmd = MI_STORE_DWORD_IMM_GEN4. Sorry about
that.

-- 
Ben Widawsky, Intel Open Source Technology Center
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