drm/i915: Ensure that while(INREG()) are bounded (v2)
Add a new macro, wait_for, to simplify the act of waiting on a register
to change state. wait_for() takes three arguments, the condition to
inspect on every loop, the maximum amount of time to wait and whether to
yield the cpu for a length of time after each check.
v2: Upgrade failure messages to DRM_ERROR on the suggestion of
Eric Anholt. We do not expect to hit these conditions as they reflect
programming errors, so if we do we want to be notified.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Eric Anholt <eric@anholt.net>
diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index c552b06..2a3eaaf 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -32,6 +32,20 @@
#include "drm_crtc.h"
#include "drm_crtc_helper.h"
+
+#define wait_for(COND, MS, W) ({ \
+ unsigned long timeout__ = jiffies + msecs_to_jiffies(MS); \
+ int ret__ = 0; \
+ while (! (COND)) { \
+ if (time_after(jiffies, timeout__)) { \
+ ret__ = -ETIMEDOUT; \
+ break; \
+ } \
+ if (W) msleep(W); \
+ } \
+ ret__; \
+})
+
/*
* Display related stuff
*/