Re: [Intel-gfx] [PATCH] drm/i915: Read a shadowed mmio register for ggtt flush

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 




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



[Index of Archives]     [Linux DRI Users]     [Linux Intel Graphics]     [Linux USB Devel]     [Video for Linux]     [Linux Audio Users]     [Yosemite News]     [Linux Kernel]     [Linux SCSI]     [XFree86]     [Linux USB Devel]     [Video for Linux]     [Linux Audio Users]     [Linux Kernel]     [Linux SCSI]     [XFree86]
  Powered by Linux