scsi: ufs: core: Reset urgent_bkops_lvl to allow runtime PM power mode

Ensures that UFS Runtime PM can achieve power saving after System PM
suspend by resetting hba->urgent_bkops_lvl. Also modify the
ufshcd_bkops_exception_event_handler to avoid setting urgent_bkops_lvl when
status is 0, which helps maintain optimal power management.

On UFS devices supporting UFSHCD_CAP_AUTO_BKOPS_SUSPEND, a BKOPS exception
event can lead to a situation where UFS Runtime PM can't enter low-power
mode states even after the BKOPS exception has been resolved.

BKOPS exception with bkops status 0 occurs, the driver logs:

 "ufshcd_bkops_exception_event_handler: device raised urgent BKOPS exception for bkops status 0"

When a BKOPS exception occurs, ufshcd_bkops_exception_event_handler() reads
the BKOPS status and sets hba->urgent_bkops_lvl to BKOPS_STATUS_NO_OP(0).
This allows the device to perform Runtime PM without changing the UFS power
mode.  (__ufshcd_wl_suspend(hba, UFS_RUNTIME_PM))

During system PM suspend, ufshcd_disable_auto_bkops() is called, disabling
auto bkops. After UFS System PM Resume, when runtime PM attempts to suspend
again, ufshcd_urgent_bkops() is invoked. Since hba->urgent_bkops_lvl
remains at BKOPS_STATUS_NO_OP(0), ufshcd_enable_auto_bkops() is triggered.

However, in ufshcd_bkops_ctrl(), the driver compares the current BKOPS
status with hba->urgent_bkops_lvl, and only enables auto bkops if
curr_status >= hba->urgent_bkops_lvl.  Since both values are 0, the
condition is met

As a result, __ufshcd_wl_suspend(hba, UFS_RUNTIME_PM) skips power mode
transitions and remains in an active state, preventing power saving even
though no urgent BKOPS condition exists.

Signed-off-by: Won Jung <wone.jung@samsung.com>
Reviewed-by: Peter Wang <peter.wang@mediatek.com>
Link: https://patch.msgid.link/1891546521.01770806581968.JavaMail.epsvc@epcpadp2new
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

0 files changed, 0 insertions, 0 deletions