[Intel-gfx] [PATCH 2/4] drm/i915: use cpu_relax() in wait_for_atomic

[Ben Widawsky]

As part of the advice given to us from the hardware designers regarding
the maximum wait time on the forcewake handshake we need to move from us
granularity to ms granularity. In earlier patches to do this, Jani
noticed that wait_for_us was properly converted to use cpu_relax(), but
wait_for was not.

The issue has existed since the introduction of the macro:
commit 913d8d110078788c14812dce8bb62c37946821d2
Author: Chris Wilson <chris at chris-wilson.co.uk>
Date:   Sat Aug 7 11:01:35 2010 +0100

    drm/i915: Ensure that while(INREG()) are bounded (v2)

CC: Jani Nikula <jani.nikula at linux.intel.com>
Signed-off-by: Ben Widawsky <ben at bwidawsk.net>
---
 drivers/gpu/drm/i915/intel_drv.h | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index 95f635b..1707de5 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -41,7 +41,11 @@
 			ret__ = -ETIMEDOUT;				\
 			break;						\
 		}							\
-		if (W && drm_can_sleep()) msleep(W);	\
+		if (W && drm_can_sleep())  {				\
+			msleep(W);					\
+		} else {						\
+			cpu_relax();					\
+		}							\
 	}								\
 	ret__;								\
 })
-- 
1.7.12