leandrof/linux
1
0
Fork 0
forked from Minki/linux
Code Issues Pull Requests Packages Projects Releases Wiki Activity

drm/etnaviv: correct timeout calculation

Browse Source 
The old way did clamp the jiffy conversion and thus caused the timeouts
to become negative after some time. Also it didn't work with userspace
which actually fills the upper 32bits of the 64bit timestamp value.

clock_gettime() is 32-bit on 32-bit architectures. Using 64-bit timespec
math, like we do in this commit, means that when a wrap occurs, the
specified timeout goes into the past and we can't request a timeout in
the future. As the Linux implementation of CLOCK_MONOTONIC is reasonable
and starts at 0, the first such timer wrap will occur after approx. 68
years of system uptime.

Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
This commit is contained in:
Russell King 2018-02-20 10:22:22 +01:00 committed by Lucas Stach
parent 60cc43fc88
commit d066b246d4
1 changed files with 17 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

25
drivers/gpu/drm/etnaviv/etnaviv_drv.h
View File

@ -26,6 +26,7 @@
#include <linux/pm_runtime.h>
#include <linux/slab.h>
#include <linux/list.h>
#include <linux/time64.h>
#include <linux/types.h>
#include <linux/sizes.h>
@ -132,19 +133,27 @@ static inline bool fence_after_eq(u32 a, u32 b)
return (s32)(a - b) >= 0;
}
/*
* Etnaviv timeouts are specified wrt CLOCK_MONOTONIC, not jiffies.
* We need to calculate the timeout in terms of number of jiffies
* between the specified timeout and the current CLOCK_MONOTONIC time.
*/
static inline unsigned long etnaviv_timeout_to_jiffies(
const struct timespec *timeout)
{
unsigned long timeout_jiffies = timespec_to_jiffies(timeout);
unsigned long start_jiffies = jiffies;
unsigned long remaining_jiffies;
struct timespec64 ts, to;
if (time_after(start_jiffies, timeout_jiffies))
remaining_jiffies = 0;
else
remaining_jiffies = timeout_jiffies - start_jiffies;
to = timespec_to_timespec64(*timeout);
return remaining_jiffies;
ktime_get_ts64(&ts);
/* timeouts before "now" have already expired */
if (timespec64_compare(&to, &ts) <= 0)
return 0;
ts = timespec64_sub(to, ts);
return timespec64_to_jiffies(&ts);
}
#endif /* __ETNAVIV_DRV_H__ */