Check for overflow in udelay/usleep_range use in __xe_mmio_wait32
and pick the correct helper according to the wait time and atomic.
Implement a similar helper to replace DIV_ROUND_UP for 32-bit CPUs.
Avoid growing delays becoming intollerably large by capping the
in-loop wait time.
v3: - Use div64_s64 kernel API for 32-bit vs 64-bit division.
v2: - Fixed checkpatch failure.
- Added helper for 64-bit DIV_ROUND_UP on 32-bit CPU (Shasiko
review). Fixed bug max range in usleep_range(Shasiko review)
Fixes: 5c09bd6ccd41 ("drm/xe/mmio: Move xe_mmio_wait32() to xe_mmio.c")
Signed-off-by: Alan Previn <[email protected]>
Assisted-by: Github-Copilot:Claude-Sonnet-5-0
---
drivers/gpu/drm/xe/xe_mmio.c | 23 ++++++++++++++++++-----
1 file changed, 18 insertions(+), 5 deletions(-)
diff --git a/drivers/gpu/drm/xe/xe_mmio.c b/drivers/gpu/drm/xe/xe_mmio.c
index 7fa18dfcb5a2..507095f33cec 100644
--- a/drivers/gpu/drm/xe/xe_mmio.c
+++ b/drivers/gpu/drm/xe/xe_mmio.c
@@ -7,6 +7,7 @@
#include <linux/delay.h>
#include <linux/io-64-nonatomic-lo-hi.h>
+#include <linux/math64.h>
#include <linux/minmax.h>
#include <linux/pci.h>
@@ -349,11 +350,23 @@ static int __xe_mmio_wait32(struct xe_mmio *mmio, struct
xe_reg reg, u32 mask, u
if (ktime_after(ktime_add_us(cur, wait), end))
wait = ktime_us_delta(end, cur);
- if (atomic)
- udelay(wait);
- else
- usleep_range(wait, wait << 1);
- wait <<= 1;
+#define __XE_MMIO_WAIT_MAX_INLOOP_100MS (100 * USEC_PER_MSEC)
+ if (atomic) {
+ if (wait <= MAX_UDELAY_MS * USEC_PER_MSEC)
+ udelay(wait);
+ else
+ mdelay(div64_s64(wait, USEC_PER_MSEC));
+ } else {
+ usleep_range(wait, wait + (wait >> 2)); /* range till
wait + 25% */
+ }
+ /*
+ * As we keep doubling the wait time for every check that
fails, cap the
+ * in-loop delay-or-sleep to less than 2x 100 milliseconds to
prevent from
+ * expanding 'wait' into exponentially longer wait times per
loop that
+ * end up delaying the next completion check way later than
tolerable.
+ */
+ wait = wait < __XE_MMIO_WAIT_MAX_INLOOP_100MS >> 1 ?
+ wait << 1 : __XE_MMIO_WAIT_MAX_INLOOP_100MS;
}
if (ret != 0) {
--
2.43.0
