On 10/21, Can Guo wrote: > On 2020-10-21 03:52, Jaegeuk Kim wrote: > > The below call stack prevents clk_gating at every IO completion. > > We can remove the condition, ufshcd_any_tag_in_use(), since > > clkgating_work > > will check it again. > > > > I think checking ufshcd_any_tag_in_use() in either ufshcd_release() or > gate_work() can break UFS clk gating's functionality. > > ufshcd_any_tag_in_use() was introduced to replace hba->lrb_in_use. However, > they are not exactly same - ufshcd_any_tag_in_use() returns true if any tag > assigned from block layer is still in use, but tags are released > asynchronously > (through block softirq), meaning it does not reflect the real occupation of > UFS host. > That is after UFS host finishes all tasks, ufshcd_any_tag_in_use() can still > return true. > > This change only removes the check of ufshcd_any_tag_in_use() in > ufshcd_release(), > but having the check of it in gate_work() can still prevent gating from > happening. > The current change works for you maybe because the tags are release before > hba->clk_gating.delay_ms expires, but if hba->clk_gating.delay_ms is shorter > or > somehow block softirq is retarded, gate_work() may have chance to see > ufshcd_any_tag_in_use() > returns true. What do you think? I don't think this breaks clkgating, but fix the wrong condition check which prevented gate_work at all. As you mentioned, even if this schedules gate_work by racy conditions, gate_work will handle it as a last resort. > > Thanks, > > Can Guo. > > In __ufshcd_transfer_req_compl > Ihba->lrb_in_use is cleared immediately when UFS driver > finishes all tasks > > > ufshcd_complete_requests(struct ufs_hba *hba) > > ufshcd_transfer_req_compl() > > __ufshcd_transfer_req_compl() > > __ufshcd_release(hba) > > if (ufshcd_any_tag_in_use() == 1) > > return; > > ufshcd_tmc_handler(hba); > > blk_mq_tagset_busy_iter(); > > > > Cc: Alim Akhtar <alim.akhtar@xxxxxxxxxxx> > > Cc: Avri Altman <avri.altman@xxxxxxx> > > Cc: Can Guo <cang@xxxxxxxxxxxxxx> > > Signed-off-by: Jaegeuk Kim <jaegeuk@xxxxxxxxxx> > > --- > > drivers/scsi/ufs/ufshcd.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c > > index b5ca0effe636..cecbd4ace8b4 100644 > > --- a/drivers/scsi/ufs/ufshcd.c > > +++ b/drivers/scsi/ufs/ufshcd.c > > @@ -1746,7 +1746,7 @@ static void __ufshcd_release(struct ufs_hba *hba) > > > > if (hba->clk_gating.active_reqs || hba->clk_gating.is_suspended || > > hba->ufshcd_state != UFSHCD_STATE_OPERATIONAL || > > - ufshcd_any_tag_in_use(hba) || hba->outstanding_tasks || > > + hba->outstanding_tasks || > > hba->active_uic_cmd || hba->uic_async_done) > > return;
