From: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
Currently the wait_for_atomic_us only allows for a millisecond
granularity which is not nice towards callers requesting small
micro-second waits.
Re-implement it so micro-second granularity is really supported
and not just in the name of the macro.
v2:
* Warn when used from non-atomic context (if possible).
* Warn on too long atomic waits.
v3:
* Added comment explaining CONFIG_PREEMPT_COUNT.
* Fixed pre-processor indentation.
(Chris Wilson)
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Reviewed-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
---
drivers/gpu/drm/i915/intel_drv.h | 31 +++++++++++++++++++++++++++++--
1 file changed, 29 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index 93da5ee2b09e..90e14bfdded6 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -44,6 +44,10 @@
* contexts. Note that it's important that we check the condition again after
* having timed out, since the timeout could be due to preemption or similar and
* we've never had a chance to check the condition before the timeout.
+ *
+ * TODO: When modesetting has fully transitioned to atomic, the below
+ * drm_can_sleep() can be removed and in_atomic()/!in_atomic() asserts
+ * added.
*/
#define _wait_for(COND, US, W) ({ \
unsigned long timeout__ = jiffies + usecs_to_jiffies(US) + 1; \
@@ -66,8 +70,31 @@
#define wait_for(COND, MS) _wait_for((COND), (MS) * 1000, 1000)
#define wait_for_us(COND, US) _wait_for((COND), (US), 1)
-#define wait_for_atomic(COND, MS) _wait_for((COND), (MS) * 1000, 0)
-#define wait_for_atomic_us(COND, US) _wait_for((COND), (US), 0)
+/* 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())
+#else
+# define _WAIT_FOR_ATOMIC_CHECK do { } while(0)
+#endif
+
+#define _wait_for_atomic(COND, US) ({ \
+ unsigned long end__; \
+ int ret__ = 0; \
+ _WAIT_FOR_ATOMIC_CHECK; \
+ BUILD_BUG_ON((US) > 50000); \
+ end__ = (local_clock() >> 10) + (US) + 1; \
+ while (!(COND)) { \
+ if (time_after((unsigned long)(local_clock() >> 10), end__)) { \
+ ret__ = -ETIMEDOUT; \
+ break; \
+ } \
+ cpu_relax(); \
+ } \
+ 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 KHz(x) (1000 * (x))
#define MHz(x) KHz(1000 * (x))
--
1.9.1
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