[Intel-gfx] [PATCH 1/4] drm/i915: make unclaimed registers be errors again

[Paulo Zanoni]

Fixes an issue introduced by:

commit 48572edd9d736d6fabd40b810a0de844ee4f800b
Author: Chris Wilson <chris at chris-wilson.co.uk>
Date:   Thu Dec 18 10:55:50 2014 +0000
    drm/i915: Disable the mmio.debug WARN after it fires

Since the above commit, on the default use case - i915.mmio_debug=0 -,
whenever we detect a single access to an unclaimed register we will
print a DRM_DEBUG() message that is very likely to get ignored by
pretty much everybody, including PRTS and QA. Of course, we will
increment i915.mmio_debug, and then the next time a problem happens we
will print a big WARN(), but then if we never ever hit the same
problem again, the error will go unnoticed.

The case I imagine here is the following: we have a platform with no
unclaimed register errors happening, then someone submits a patch that
does just one wrong access (e.g., when loading the driver). That bad
register access gets noticed, we print DRM_DEBUG(), but then our QA
processes won't notice the problem until someone introduces a second
unclaimed register bug to trigger the WARN. We'll probably not even
get a bug report for that once the problem reaches the general
audience.

So what this patch does is to make sure we print an error message even
if we only ever detect a single unclaimed register problem in order to
not hide the possible bugs.

Cc: Chris Wilson <chris at chris-wilson.co.uk>
Signed-off-by: Paulo Zanoni <paulo.r.zanoni at intel.com>
---
 drivers/gpu/drm/i915/intel_uncore.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/intel_uncore.c b/drivers/gpu/drm/i915/intel_uncore.c
index dec20d6..10c61a6 100644
--- a/drivers/gpu/drm/i915/intel_uncore.c
+++ b/drivers/gpu/drm/i915/intel_uncore.c
@@ -631,7 +631,7 @@ hsw_unclaimed_reg_detect(struct drm_i915_private *dev_priv)
 		return;
 
 	if (__raw_i915_read32(dev_priv, FPGA_DBG) & FPGA_DBG_RM_NOCLAIM) {
-		DRM_DEBUG("Unclaimed register detected, "
+		DRM_ERROR("Unclaimed register detected, "
 			  "enabling oneshot unclaimed register reporting. "
 			  "Please use i915.mmio_debug=N for more information.\n");
 		__raw_i915_write32(dev_priv, FPGA_DBG, FPGA_DBG_RM_NOCLAIM);
-- 
2.5.0