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drm/i915: Replace WARN inside I915_READ64_2x32 with retry loop 

Since we may conceivably encounter situations where the upper part of the
64bit register changes between reads, for example when a timestamp
counter overflows, change the WARN into a retry loop.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Michał Winiarski <michal.winiarski@intel.com>
Cc: stable@vger.kernel.org
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
This commit is contained in:
Chris Wilson 2015-07-15 09:50:42 +01:00 committed by Daniel Vetter
parent cbfe8fa6cd
commit ee0a227b7a
1 changed files with 8 additions and 9 deletions
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11
drivers/gpu/drm/i915/i915_drv.h
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@ -3303,14 +3303,13 @@ int intel_freq_opcode(struct drm_i915_private *dev_priv, int val);
#define I915_READ64(reg) dev_priv->uncore.funcs.mmio_readq(dev_priv, (reg), true)
#define I915_READ64_2x32(lower_reg, upper_reg) ({ \
u32 upper = I915_READ(upper_reg); \
u32 lower = I915_READ(lower_reg); \
u32 tmp = I915_READ(upper_reg); \
if (upper != tmp) { \
u32 upper, lower, tmp; \
tmp = I915_READ(upper_reg); \
do { \
upper = tmp; \
lower = I915_READ(lower_reg); \
WARN_ON(I915_READ(upper_reg) != upper); \
} \
tmp = I915_READ(upper_reg); \
} while (upper != tmp); \
(u64)upper << 32 | lower; })
#define POSTING_READ(reg) (void)I915_READ_NOTRACE(reg)