scsi: ufs: core: Serialize AHIT register access between sysfs and host driver

A race exists between ufshcd_auto_hibern8_update() and
ufs_mtk_pwr_change_notify() when both paths concurrently access
REG_AUTO_HIBERNATE_IDLE_TIMER. Additionally, the static local variable used
to save/restore AHIT in the power change path is not re-entrant and may
hold a stale value if a sysfs write races with a gear change.

Introduce ahit_mutex and ahit_disable_depth in struct ufs_hba to
serialize AHIT register access. The depth counter tracks how many
host-driver paths have forced AHIT off; sysfs writes are suppressed
while it is non-zero and the register is restored from hba->ahit
only when the last disabler drops it to zero.

Fixes: f5ca8d0c7a63 ("scsi: ufs: host: mediatek: Disable auto-hibern8 during power mode changes")
Signed-off-by: Peter Wang <peter.wang@mediatek.com>
Reviewed-by: Chun-Hung Wu <chun-hung.wu@mediatek.com>
Link: https://patch.msgid.link/20260914085148.136429-3-peter.wang@mediatek.com
Signed-off-by: Martin K. Petersen (Oracle) <mkp@kernel.org>

0 files changed, 0 insertions, 0 deletions