[PATCH] drm/xe/mmio: Fix xe_mmio_wait32() to honor delay/sleep maximums

[Alan Previn <alan.previn.teres.alexis@intel.com>]

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.

v6: - Fix commit message to remove items dropped in v5. Fix the
      use of MAX_UDELAY_MS for microsecond unit. (Shasiko review).
v5: - Simplify: don't introduce additional redesign and
      use min_t with a backoff to cap wait. (Rodrigo).
v4: - Simplify using poll_timeout_us and poll_timeout_us_atomic and
      update all callers to never use a param for atomic (Jani)
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 <alan.previn.teres.alexis@intel.com>
Assisted-by: Github-Copilot:Claude-Sonnet-5-0
---
 drivers/gpu/drm/xe/xe_mmio.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/xe/xe_mmio.c b/drivers/gpu/drm/xe/xe_mmio.c
index 7fa18dfcb5a2..5a03698729ce 100644
--- a/drivers/gpu/drm/xe/xe_mmio.c
+++ b/drivers/gpu/drm/xe/xe_mmio.c
@@ -350,10 +350,11 @@ static int __xe_mmio_wait32(struct xe_mmio *mmio, struct xe_reg reg, u32 mask, u
 			wait = ktime_us_delta(end, cur);
 
 		if (atomic)
-			udelay(wait);
+			udelay(min_t(s64, wait, (MAX_UDELAY_MS * 1000)));
 		else
 			usleep_range(wait, wait << 1);
-		wait <<= 1;
+#define __XE_MMIO_WAIT_MAX_BACKOFF_100MS (100 * USEC_PER_MSEC)
+		wait = min_t(s64, wait << 1, __XE_MMIO_WAIT_MAX_BACKOFF_100MS);
 	}
 
 	if (ret != 0) {
-- 
2.43.0