[16/26] drm/i915: Update execlists context descriptor format commentary

Submitted by Chris Wilson on April 26, 2016, 10:49 a.m.

Details

Message ID 1461667798-31998-16-git-send-email-chris@chris-wilson.co.uk
State New
Headers show
Series "Series without cover letter" ( rev: 1 ) in Intel GFX - Try Bot

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Commit Message

Chris Wilson April 26, 2016, 10:49 a.m.
The comments describing the Context Descriptor Format are off by a bit
for the size of the context ID.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Dave Gordon <david.s.gordon@intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
---
 drivers/gpu/drm/i915/intel_lrc.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

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diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
index 7d5186e17317..01739259ca50 100644
--- a/drivers/gpu/drm/i915/intel_lrc.c
+++ b/drivers/gpu/drm/i915/intel_lrc.c
@@ -305,10 +305,11 @@  logical_ring_init_platform_invariants(struct intel_engine_cs *engine)
  * which remains valid until the context is unpinned.
  *
  * This is what a descriptor looks like, from LSB to MSB:
- *    bits 0-11:    flags, GEN8_CTX_* (cached in ctx_desc_template)
+ *    bits  0-11:    flags, GEN8_CTX_* (cached in ctx_desc_template)
  *    bits 12-31:    LRCA, GTT address of (the HWSP of) this context
- *    bits 32-51:    ctx ID, a globally unique tag (the LRCA again!)
- *    bits 52-63:    reserved, may encode the engine ID (for GuC)
+ *    bits 32-52:    ctx ID, a globally unique tag (the LRCA again!)
+ *    bits 52-54:    mbz, reserved for use by hardware
+ *    bits 55-63:    group ID, currently unused and set to 0
  */
 static void
 intel_lr_context_descriptor_update(struct intel_context *ctx,
@@ -319,9 +320,9 @@  intel_lr_context_descriptor_update(struct intel_context *ctx,
 	lrca = ctx->engine[engine->id].lrc_vma->node.start +
 	       LRC_PPHWSP_PN * PAGE_SIZE;
 
-	desc = engine->ctx_desc_template;			   /* bits  0-11 */
+	desc = engine->ctx_desc_template;		   /* bits  0-11 */
 	desc |= lrca;					   /* bits 12-31 */
-	desc |= (lrca >> PAGE_SHIFT) << GEN8_CTX_ID_SHIFT; /* bits 32-51 */
+	desc |= (lrca >> PAGE_SHIFT) << GEN8_CTX_ID_SHIFT; /* bits 32-52 */
 
 	ctx->engine[engine->id].lrc_desc = desc;
 }