Re: [Intel-gfx] [PATCH v2 2/2] drm/i915: Check for unreliable MMIO during forcewake

[Andrzej Hajda]

On 21.03.2023 18:09, Andi Shyti wrote:
From: Matt Roper <matthew.d.ro...@intel.com>
Although we now sanitycheck MMIO access during driver load to make sure
the MMIO BAR isn't returning all 0xFFFFFFFF, there have been a few cases
where (temporarily?) unreliable MMIO access has happened after GPU
resets or power events.  We'll often notice this on our next GT register
access since forcewake handling will fail; let's change our handling
slightly so that when this happens we print a more meaningful message
clarifying that the problem is the MMIO access, not forcewake
specifically.

Signed-off-by: Matt Roper <matthew.d.ro...@intel.com>
Cc: Mika Kuoppala <mika.kuopp...@linux.intel.com>
Signed-off-by: Andi Shyti <andi.sh...@linux.intel.com>
---
  drivers/gpu/drm/i915/intel_uncore.c | 12 +++++++++---
  1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_uncore.c 
b/drivers/gpu/drm/i915/intel_uncore.c
index 0b69081d6d285..303a5d38c93a5 100644
--- a/drivers/gpu/drm/i915/intel_uncore.c
+++ b/drivers/gpu/drm/i915/intel_uncore.c
@@ -178,9 +178,15 @@ static inline void
  fw_domain_wait_ack_clear(const struct intel_uncore_forcewake_domain *d)
  {
        if (wait_ack_clear(d, FORCEWAKE_KERNEL)) {
-               drm_err(&d->uncore->i915->drm,
-                       "%s: timed out waiting for forcewake ack to clear.\n",
-                       intel_uncore_forcewake_domain_to_str(d->id));
+               if (fw_ack(d) == ~0)
+                       drm_err(&d->uncore->i915->drm,
+                               "%s: MMIO unreliable (forcewake register returns 
0xFFFFFFFF)!\n",
+                               intel_uncore_forcewake_domain_to_str(d->id));
+               else
+                       drm_err(&d->uncore->i915->drm,
+                               "%s: timed out waiting for forcewake ack to 
clear.\n",
+                               intel_uncore_forcewake_domain_to_str(d->id));
+
With:

if (!wait_ack_clear(...))
        return;

you do not need to indent.
And since drm_err have the same set of args in both cases, except fmt, 
it could be also simplified.

Anyway I am not sure if it is worth effort, so:
Reviewed-by: Andrzej Hajda <andrzej.ha...@intel.com>

Regards
Andrzej


                add_taint_for_CI(d->uncore->i915, TAINT_WARN); /* CI now 
unreliable */
        }
  }