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authorTvrtko Ursulin <tvrtko.ursulin@intel.com>2016-06-29 12:27:22 +0100
committerTvrtko Ursulin <tvrtko.ursulin@intel.com>2016-06-29 15:53:15 +0100
commit18f4b8435c50888bb36cf8de3b7f0075f00dc12c (patch)
tree22fc1a86c1c0461f418df08faccce9e92540d664
parentc68b0ab2e08fd8913a794d11e74cbf5cd589b3df (diff)
drm/i915: Use atomic waits for short non-atomic ones
usleep_range is not recommended for waits shorten than 10us. Make the wait_for_us use the atomic variant for such waits. To do so we need to reimplement the _wait_for_atomic macro to be safe with regards to preemption and interrupts. v2: Reimplement _wait_for_atomic to be irq and preemption safe. (Chris Wilson and Imre Deak) v3: Fixed in_atomic check due rebase error. v4: Build bug on non-constant timeouts. v5: Compile away cpu migration code in atomic paths. Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com> Cc: Chris Wilson <chris@chris-wilson.co.uk> Cc: Imre Deak <imre.deak@intel.com> Cc: Mika Kuoppala <mika.kuoppala@intel.com> Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk> Link: http://patchwork.freedesktop.org/patch/msgid/1467114710-29989-1-git-send-email-tvrtko.ursulin@linux.intel.com
-rw-r--r--drivers/gpu/drm/i915/intel_drv.h62
1 files changed, 43 insertions, 19 deletions
diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index 3156d8df7921..98a5be4ec8c5 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -69,39 +69,63 @@
})
#define wait_for(COND, MS) _wait_for((COND), (MS) * 1000, 1000)
-#define wait_for_us(COND, US) _wait_for((COND), (US), 1)
/* If CONFIG_PREEMPT_COUNT is disabled, in_atomic() always reports false. */
#if defined(CONFIG_DRM_I915_DEBUG) && defined(CONFIG_PREEMPT_COUNT)
-# define _WAIT_FOR_ATOMIC_CHECK WARN_ON_ONCE(!in_atomic())
+# define _WAIT_FOR_ATOMIC_CHECK(ATOMIC) WARN_ON_ONCE((ATOMIC) && !in_atomic())
#else
-# define _WAIT_FOR_ATOMIC_CHECK do { } while (0)
+# define _WAIT_FOR_ATOMIC_CHECK(ATOMIC) do { } while (0)
#endif
-#define _wait_for_atomic(COND, US) ({ \
- unsigned long end__; \
- int ret__ = 0; \
- _WAIT_FOR_ATOMIC_CHECK; \
+#define _wait_for_atomic(COND, US, ATOMIC) \
+({ \
+ int cpu, ret, timeout = (US) * 1000; \
+ u64 base; \
+ _WAIT_FOR_ATOMIC_CHECK(ATOMIC); \
BUILD_BUG_ON((US) > 50000); \
- end__ = (local_clock() >> 10) + (US) + 1; \
- while (!(COND)) { \
- if (time_after((unsigned long)(local_clock() >> 10), end__)) { \
- /* Unlike the regular wait_for(), this atomic variant \
- * cannot be preempted (and we'll just ignore the issue\
- * of irq interruptions) and so we know that no time \
- * has passed since the last check of COND and can \
- * immediately report the timeout. \
- */ \
- ret__ = -ETIMEDOUT; \
+ if (!(ATOMIC)) { \
+ preempt_disable(); \
+ cpu = smp_processor_id(); \
+ } \
+ base = local_clock(); \
+ for (;;) { \
+ u64 now = local_clock(); \
+ if (!(ATOMIC)) \
+ preempt_enable(); \
+ if (COND) { \
+ ret = 0; \
+ break; \
+ } \
+ if (now - base >= timeout) { \
+ ret = -ETIMEDOUT; \
break; \
} \
cpu_relax(); \
+ if (!(ATOMIC)) { \
+ preempt_disable(); \
+ if (unlikely(cpu != smp_processor_id())) { \
+ timeout -= now - base; \
+ cpu = smp_processor_id(); \
+ base = local_clock(); \
+ } \
+ } \
} \
+ ret; \
+})
+
+#define wait_for_us(COND, US) \
+({ \
+ int ret__; \
+ BUILD_BUG_ON(!__builtin_constant_p(US)); \
+ if ((US) > 10) \
+ ret__ = _wait_for((COND), (US), 10); \
+ else \
+ ret__ = _wait_for_atomic((COND), (US), 0); \
ret__; \
})
-#define wait_for_atomic(COND, MS) _wait_for_atomic((COND), (MS) * 1000)
-#define wait_for_atomic_us(COND, US) _wait_for_atomic((COND), (US))
+#define wait_for_atomic(COND, MS) _wait_for_atomic((COND), (MS) * 1000, 1)
+#define wait_for_atomic_us(COND, US) _wait_for_atomic((COND), (US), 1)
#define KHz(x) (1000 * (x))
#define MHz(x) KHz(1000 * (x))