drm/i915: Update execlists context descriptor format commentary
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>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1461833819-3991-16-git-send-email-chris@chris-wilson.co.uk
diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
index 4dedeaa..2178741 100644
--- a/drivers/gpu/drm/i915/intel_lrc.c
+++ b/drivers/gpu/drm/i915/intel_lrc.c
@@ -305,10 +305,11 @@
* 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 53-54: 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 @@
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;
}