drm_timeout_abs_to_jiffies() covers the drivers whose wait UAPI takes an absolute deadline, but there is no equivalent for the drivers that express a wait as a duration. Drivers such as i915 and v3d convert the value themselves.
Converting a nanosecond duration to jiffies needs some care. nsecs_to_jiffies() returns unsigned long, so on 32-bit a large userspace-supplied timeout overflows its range and is silently truncated. i915 already handles both cases in a local helper, which v3d has a copy of. Add the same conversion to the core, so that it is available to any driver and both copies can be dropped. Signed-off-by: Maíra Canal <[email protected]> --- drivers/gpu/drm/drm_timeout.c | 29 +++++++++++++++++++++++++++++ include/drm/drm_utils.h | 1 + 2 files changed, 30 insertions(+) diff --git a/drivers/gpu/drm/drm_timeout.c b/drivers/gpu/drm/drm_timeout.c index 78e9f65e5477..30ad3e8ebc92 100644 --- a/drivers/gpu/drm/drm_timeout.c +++ b/drivers/gpu/drm/drm_timeout.c @@ -9,6 +9,7 @@ #include <linux/export.h> #include <linux/jiffies.h> #include <linux/ktime.h> +#include <linux/math64.h> #include <linux/sched.h> #include <drm/drm_utils.h> @@ -45,3 +46,31 @@ signed long drm_timeout_abs_to_jiffies(int64_t timeout_nsec) return timeout_jiffies64 + 1; } EXPORT_SYMBOL(drm_timeout_abs_to_jiffies); + +/** + * drm_timeout_rel_to_jiffies - calculate jiffies timeout from relative value + * + * @timeout_nsec: relative timeout in ns, 0 for poll + * + * Calculate the timeout in jiffies from a relative timeout in ns, for drivers + * whose UAPI expresses a wait as a duration rather than as a deadline. + * + * The result is clamped to MAX_JIFFY_OFFSET. That keeps it positive once it is + * converted to the signed long taken by dma_fence_wait_timeout() and friends, + * which matters on 32-bit, and keeps it distinct from MAX_SCHEDULE_TIMEOUT so + * that a finite wait is never understood as an infinite one. + */ +unsigned long drm_timeout_rel_to_jiffies(u64 timeout_nsec) +{ + /* make 0 timeout means poll, as for the absolute variant */ + if (timeout_nsec == 0) + return 0; + + /* nsecs_to_jiffies64() does not guard against overflow */ + if ((NSEC_PER_SEC % HZ) != 0 && + div_u64(timeout_nsec, NSEC_PER_SEC) >= MAX_JIFFY_OFFSET / HZ) + return MAX_JIFFY_OFFSET; + + return min_t(u64, MAX_JIFFY_OFFSET, nsecs_to_jiffies64(timeout_nsec) + 1); +} +EXPORT_SYMBOL(drm_timeout_rel_to_jiffies); diff --git a/include/drm/drm_utils.h b/include/drm/drm_utils.h index 6a46f755daba..8c0cc9835413 100644 --- a/include/drm/drm_utils.h +++ b/include/drm/drm_utils.h @@ -25,5 +25,6 @@ const struct drm_panel_backlight_quirk * drm_get_panel_backlight_quirk(const struct drm_edid *edid); signed long drm_timeout_abs_to_jiffies(int64_t timeout_nsec); +unsigned long drm_timeout_rel_to_jiffies(u64 timeout_nsec); #endif -- 2.55.0
