1 files changed, 16 insertions, 4 deletions

diff --git a/drivers/i2c/busses/i2c-s3c2410.c b/drivers/i2c/busses/i2c-s3c2410.c
index d784c76ae3e..e93e7d67277 100644
--- a/drivers/i2c/busses/i2c-s3c2410.c
+++ b/drivers/i2c/busses/i2c-s3c2410.c
@@ -554,6 +554,7 @@ static void s3c24xx_i2c_wait_idle(struct s3c24xx_i2c *i2c)
         unsigned long iicstat;
         ktime_t start, now;
         unsigned long delay;
+        int spins;
 
         /* ensure the stop has been through the bus */
 
@@ -566,12 +567,23 @@ static void s3c24xx_i2c_wait_idle(struct s3c24xx_i2c *i2c)
          * end of a transaction.  However, really slow i2c devices can stretch
          * the clock, delaying STOP generation.
          *
-         * As a compromise between idle detection latency for the normal, fast
-         * case, and system load in the slow device case, use an exponential
-         * back off in the polling loop, up to 1/10th of the total timeout,
-         * then continue to poll at a constant rate up to the timeout.
+         * On slower SoCs this typically happens within a very small number of
+         * instructions so busy wait briefly to avoid scheduling overhead.
          */
+        spins = 3;
         iicstat = readl(i2c->regs + S3C2410_IICSTAT);
+        while ((iicstat & S3C2410_IICSTAT_START) && --spins) {
+                cpu_relax();
+                iicstat = readl(i2c->regs + S3C2410_IICSTAT);
+        }
+
+        /*
+         * If we do get an appreciable delay as a compromise between idle
+         * detection latency for the normal, fast case, and system load in the
+         * slow device case, use an exponential back off in the polling loop,
+         * up to 1/10th of the total timeout, then continue to poll at a
+         * constant rate up to the timeout.
+         */
         delay = 1;
         while ((iicstat & S3C2410_IICSTAT_START) &&
                ktime_us_delta(now, start) < S3C2410_IDLE_TIMEOUT) {