4.4-stable review patch. If anyone has any objections, please let me know.
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From: Venkat Gopalakrishnan venkatg@codeaurora.org
commit f2a785ac23125fa0774327d39e837e45cf28fe92 upstream.
The ungate work turns on the clock before it exits hibern8, if the link was put in hibern8 during clock gating work. There occurs a race condition when clock scaling work calls ufshcd_hold() to make sure low power states cannot be entered, but that returns by checking only whether the clocks are on. This causes the clock scaling work to issue UIC commands when the link is in hibern8 causing failures. Make sure we exit hibern8 state before returning from ufshcd_hold().
Callstacks for race condition:
ufshcd_scale_gear ufshcd_devfreq_scale ufshcd_devfreq_target update_devfreq devfreq_monitor process_one_work worker_thread kthread ret_from_fork
ufshcd_uic_hibern8_exit ufshcd_ungate_work process_one_work worker_thread kthread ret_from_fork
Signed-off-by: Venkat Gopalakrishnan venkatg@codeaurora.org Signed-off-by: Subhash Jadavani subhashj@codeaurora.org Signed-off-by: Martin K. Petersen martin.petersen@oracle.com Signed-off-by: Amit Pundir amit.pundir@linaro.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- drivers/scsi/ufs/ufshcd.c | 15 +++++++++++++++ 1 file changed, 15 insertions(+)
--- a/drivers/scsi/ufs/ufshcd.c +++ b/drivers/scsi/ufs/ufshcd.c @@ -585,6 +585,21 @@ int ufshcd_hold(struct ufs_hba *hba, boo start: switch (hba->clk_gating.state) { case CLKS_ON: + /* + * Wait for the ungate work to complete if in progress. + * Though the clocks may be in ON state, the link could + * still be in hibner8 state if hibern8 is allowed + * during clock gating. + * Make sure we exit hibern8 state also in addition to + * clocks being ON. + */ + if (ufshcd_can_hibern8_during_gating(hba) && + ufshcd_is_link_hibern8(hba)) { + spin_unlock_irqrestore(hba->host->host_lock, flags); + flush_work(&hba->clk_gating.ungate_work); + spin_lock_irqsave(hba->host->host_lock, flags); + goto start; + } break; case REQ_CLKS_OFF: if (cancel_delayed_work(&hba->clk_gating.gate_work)) {