diff options
Diffstat (limited to 'drivers')
| -rw-r--r-- | drivers/i2c/busses/i2c-s3c2410.c | 20 |
1 files changed, 16 insertions, 4 deletions
diff --git a/drivers/i2c/busses/i2c-s3c2410.c b/drivers/i2c/busses/i2c-s3c2410.c index d784c76..e93e7d6 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) { |