msm: kgsl: Fix race condition in adreno_spin_idle()

adreno_spin_idle spins for a timeout checking for gpu to idle.
Sometimes due to race conditions the timeout can occur before the
loop is executed. Change the logic to a do-while loop and add an
extra idle check after the timeout before returning failure.

CRs-Fixed: 978122
Change-Id: Idb92a0180dd8cc3e662b1ccf44d69e4bbafb29f1
Signed-off-by: Suman Tatiraju <sumant@codeaurora.org>

1 files changed, 14 insertions, 2 deletions

diff --git a/drivers/gpu/msm/adreno.c b/drivers/gpu/msm/adreno.c
index ba2533bd4c4c..337a7f2023f7 100644
--- a/drivers/gpu/msm/adreno.c
+++ b/drivers/gpu/msm/adreno.c
@@ -2165,7 +2165,7 @@ int adreno_spin_idle(struct adreno_device *adreno_dev, unsigned int timeout)
 		adreno_getreg(adreno_dev, ADRENO_REG_RBBM_STATUS) << 2,
 		0x00000000, 0x80000000);
 
-	while (time_before(jiffies, wait)) {
+	do {
 		/*
 		 * If we fault, stop waiting and return an error. The dispatcher
 		 * will clean up the fault from the work queue, but we need to
@@ -2178,7 +2178,19 @@ int adreno_spin_idle(struct adreno_device *adreno_dev, unsigned int timeout)
 
 		if (adreno_isidle(KGSL_DEVICE(adreno_dev)))
 			return 0;
-	}
+
+	} while (time_before(jiffies, wait));
+
+	/*
+	 * Under rare conditions, preemption can cause the while loop to exit
+	 * without checking if the gpu is idle. check one last time before we
+	 * return failure.
+	 */
+	if (adreno_gpu_fault(adreno_dev) != 0)
+		return -EDEADLK;
+
+	if (adreno_isidle(KGSL_DEVICE(adreno_dev)))
+		return 0;
 
 	return -ETIMEDOUT;
 }