Hi Can, On Tue, 2019-12-31 at 12:22 +0800, Stanley Chu wrote: > Hi Can, > > > > Hi Stanley, > > > > I see skipping ufshcd_set_ufs_dev_active() in ufshcd_probe_hba() > > if it is called from ufshcd_resume() path is the purpose here. > > > > If so, then ufshcd_set_dev_pwr_mode() would be called, meaning > > SSU command will be sent. Why is this SSU command needed to be > > sent after a full host reset and restore? Is ufshcd_probe_hba() > > not enough to make UFS device fully functional? > > After resume (for both runtime resume and system resume), device power > mode shall be back to "Active" to service incoming requests. > > I see two cases need device power mode transition during resume flow > 1. Device Power Mode = Sleep > 2. Device Power Mode = PowerDown > > For 1, ufshcd_probe_hba() is not invoked during resume flow, > hba->curr_dev_pwr_mode = SLEEP, thus ufshcd_resume() can invoke > ufshcd_set_dev_pwr_mode() to change device power mode. > > For 2, ufshcd_probe_hba() is invoked during resume flow, before this > fix, hba->curr_dev_pwr_mode will be set to ACTIVE (note that only this > flag is set as ACTIVE, but device may be still in PowerDown state if > device power is not fully shutdown or device HW reset is not executed > before resume), in the end, ufshcd_resume() will not invoke > ufshcd_set_dev_pwr_mode() to send SSU command to make device change back > to Active power mode. > > But if device is fully reset before resume (not by current mainstream > driver), device can be already in "Active" power mode after power on > again during resume flow. In this case, it is OK to set > hba->curr_dev_pwr_mode as ACTIVE in ufshcd_probe_hba() and SSU command > is not necessary. > > Thanks, > Stanley I think currently the assumption in ufshcd_probe_hba() that "device shall be already in Active power mode" makes sense because many device commands will be sent to device in ufshcd_probe_hba() but device is not promised to handle those commands in PowerDown power mode according to UFS spec. So, maybe always ensuring device being Active power mode before leaving ufshcd_probe_hba() is more reasonable. If so, I will drop this patch first. Thanks so much for your reviews. Happy new year! Thanks, Stanley
