On 11/9/2023 11:30 AM, Ville Syrjälä wrote:
On Thu, Nov 09, 2023 at 11:21:48AM -0800, Vinay Belgaumkar wrote:
We read RENDER_HEAD as a part of the flush. If GT is in
deeper sleep states, this could lead to read errors since we are
not using a forcewake. Safer to read a shadowed register instead.
IIRC shadowing is only thing for writes, not reads.
Sure, but reading from a shadowed register does return the cached value
(even though we don't care about the vakue here). When GT is in deeper
sleep states, it is better to read a shadowed (cached) value instead of
trying to attempt an mmio register read without a force wake anyways.
Thanks,
Vinay.
Cc: John Harrison <john.c.harrison@xxxxxxxxx>
Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio@xxxxxxxxx>
Signed-off-by: Vinay Belgaumkar <vinay.belgaumkar@xxxxxxxxx>
---
drivers/gpu/drm/i915/gt/intel_gt.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/i915/gt/intel_gt.c b/drivers/gpu/drm/i915/gt/intel_gt.c
index ed32bf5b1546..ea814ea5f700 100644
--- a/drivers/gpu/drm/i915/gt/intel_gt.c
+++ b/drivers/gpu/drm/i915/gt/intel_gt.c
@@ -451,7 +451,7 @@ void intel_gt_flush_ggtt_writes(struct intel_gt *gt)
spin_lock_irqsave(&uncore->lock, flags);
intel_uncore_posting_read_fw(uncore,
- RING_HEAD(RENDER_RING_BASE));
+ RING_TAIL(RENDER_RING_BASE));
spin_unlock_irqrestore(&uncore->lock, flags);
}
}
--
2.38.1
