Using counter based retry loops for peripherals results in the delay
being significantly overrun during high-load situations where delay
functions tend to be vary imprecise and overrun there timeouts. So
condition the termination on the actual condition of 2s for the
re-calibration to have been successful.
As this is a very long delay there is no advantage in using
high-resolution timers thus switching this to msleep().
Signed-off-by: Nicholas Mc Guire <hofrat@xxxxxxxxx>
---
V2: The maximum recalibration timeout should have been 2 * HZ as
Dmitry Torokhov <dmitry.torokhov@xxxxxxxxx> noted - V2 sets
the timeout boundary to 2s now.
Problem detected with coccinelle script (usleep_range for long delay)
The basic model for the fix up here is to use
timeout = jiffies + (retry_time)
do {
check()
mleep()
} while (time_is_after_jiffies(timeout));
rather than using a counter and have very long retry loops under load
conditions. In the specific case it is sleep()/check() though to wait
on the previous write to complete. The initial intent was to move the
usleep_range() to msleep() as the delays are very long - if this
refactoring of the timeout loop is desirable or not is not clear (both
time and count based models seem to be common).
Patch was compile tested with: x86_64_defconfig + CONFIG_MOUSE_CYAPA=m
Patch is against 4.10-rc3 (localversion-next is next-20170113)
drivers/input/mouse/cyapa_gen3.c | 27 ++++++++++++---------------
1 file changed, 12 insertions(+), 15 deletions(-)
diff --git a/drivers/input/mouse/cyapa_gen3.c b/drivers/input/mouse/cyapa_gen3.c
index f9600753..0c544de 100644
--- a/drivers/input/mouse/cyapa_gen3.c
+++ b/drivers/input/mouse/cyapa_gen3.c
@@ -789,7 +789,7 @@ static ssize_t cyapa_gen3_do_calibrate(struct device *dev,
const char *buf, size_t count)
{
struct cyapa *cyapa = dev_get_drvdata(dev);
- int tries;
+ unsigned long timeout;
int ret;
ret = cyapa_read_byte(cyapa, CYAPA_CMD_DEV_STATUS);
@@ -812,31 +812,28 @@ static ssize_t cyapa_gen3_do_calibrate(struct device *dev,
goto out;
}
- tries = 20; /* max recalibration timeout 2s. */
+ /* max recalibration timeout 2s. */
+ timeout = jiffies + 2 * HZ;
do {
/*
* For this recalibration, the max time will not exceed 2s.
* The average time is approximately 500 - 700 ms, and we
* will check the status every 100 - 200ms.
*/
- usleep_range(100000, 200000);
-
+ msleep(100);
ret = cyapa_read_byte(cyapa, CYAPA_CMD_DEV_STATUS);
if (ret < 0) {
- dev_err(dev, "Error reading dev status: %d\n",
- ret);
+ dev_err(dev, "Error reading dev status: %d\n", ret);
goto out;
}
- if ((ret & CYAPA_DEV_NORMAL) == CYAPA_DEV_NORMAL)
- break;
- } while (--tries);
+ if ((ret & CYAPA_DEV_NORMAL) == CYAPA_DEV_NORMAL) {
+ dev_dbg(dev, "Calibration successful.\n");
+ goto out;
+ }
+ } while (time_is_after_jiffies(timeout));
- if (tries == 0) {
- dev_err(dev, "Failed to calibrate. Timeout.\n");
- ret = -ETIMEDOUT;
- goto out;
- }
- dev_dbg(dev, "Calibration successful.\n");
+ dev_err(dev, "Failed to calibrate. Timeout.\n");
+ ret = -ETIMEDOUT;
out:
return ret < 0 ? ret : count;
--
2.1.4
--
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