From: Can Guo <cang@codeaurora.org> To: Jaegeuk Kim <jaegeuk@kernel.org> Cc: linux-kernel@vger.kernel.org, linux-scsi@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, kernel-team@android.com, Alim Akhtar <alim.akhtar@samsung.com>, Avri Altman <avri.altman@wdc.com> Subject: Re: [PATCH v2 5/5] scsi: ufs: fix clkgating on/off correctly Date: Wed, 21 Oct 2020 10:00:52 +0800 [thread overview] Message-ID: <2a8ecc4185b3a5411077f4e3fc66000f@codeaurora.org> (raw) In-Reply-To: <20201020195258.2005605-6-jaegeuk@kernel.org> 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? 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@samsung.com> > Cc: Avri Altman <avri.altman@wdc.com> > Cc: Can Guo <cang@codeaurora.org> > Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org> > --- > 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;
WARNING: multiple messages have this Message-ID (diff)
From: Can Guo <cang@codeaurora.org> To: Jaegeuk Kim <jaegeuk@kernel.org> Cc: linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, Avri Altman <avri.altman@wdc.com>, Alim Akhtar <alim.akhtar@samsung.com>, kernel-team@android.com Subject: Re: [f2fs-dev] [PATCH v2 5/5] scsi: ufs: fix clkgating on/off correctly Date: Wed, 21 Oct 2020 10:00:52 +0800 [thread overview] Message-ID: <2a8ecc4185b3a5411077f4e3fc66000f@codeaurora.org> (raw) In-Reply-To: <20201020195258.2005605-6-jaegeuk@kernel.org> 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? 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@samsung.com> > Cc: Avri Altman <avri.altman@wdc.com> > Cc: Can Guo <cang@codeaurora.org> > Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org> > --- > 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; _______________________________________________ Linux-f2fs-devel mailing list Linux-f2fs-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel
next prev parent reply other threads:[~2020-10-21 2:01 UTC|newest] Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-10-20 19:52 propose some UFS fixes Jaegeuk Kim 2020-10-20 19:52 ` [f2fs-dev] " Jaegeuk Kim 2020-10-20 19:52 ` [PATCH v2 1/5] scsi: ufs: atomic update for clkgating_enable Jaegeuk Kim 2020-10-20 19:52 ` [f2fs-dev] " Jaegeuk Kim 2020-10-21 2:05 ` Can Guo 2020-10-21 2:05 ` [f2fs-dev] " Can Guo 2020-10-21 4:41 ` jaegeuk 2020-10-21 4:41 ` [f2fs-dev] " jaegeuk 2020-10-20 19:52 ` [PATCH v2 2/5] scsi: ufs: clear UAC for FFU and RPMB LUNs Jaegeuk Kim 2020-10-20 19:52 ` [f2fs-dev] " Jaegeuk Kim 2020-10-20 19:52 ` [PATCH v2 3/5] scsi: ufs: use WQ_HIGHPRI for gating work Jaegeuk Kim 2020-10-20 19:52 ` [f2fs-dev] " Jaegeuk Kim 2020-10-21 0:57 ` Can Guo 2020-10-21 0:57 ` [f2fs-dev] " Can Guo 2020-10-21 4:52 ` jaegeuk 2020-10-21 4:52 ` [f2fs-dev] " jaegeuk 2020-10-20 19:52 ` [PATCH v2 4/5] scsi: add more contexts in the ufs tracepoints Jaegeuk Kim 2020-10-20 19:52 ` [f2fs-dev] " Jaegeuk Kim 2020-10-20 19:52 ` [PATCH v2 5/5] scsi: ufs: fix clkgating on/off correctly Jaegeuk Kim 2020-10-20 19:52 ` [f2fs-dev] " Jaegeuk Kim 2020-10-21 2:00 ` Can Guo [this message] 2020-10-21 2:00 ` Can Guo 2020-10-21 4:52 ` jaegeuk 2020-10-21 4:52 ` [f2fs-dev] " jaegeuk 2020-10-21 6:05 ` Can Guo 2020-10-21 6:05 ` [f2fs-dev] " Can Guo 2020-10-23 0:53 ` Jaegeuk Kim 2020-10-23 0:53 ` [f2fs-dev] " Jaegeuk Kim 2020-10-26 3:12 ` Can Guo 2020-10-26 3:12 ` [f2fs-dev] " Can Guo 2020-10-26 6:19 ` Jaegeuk Kim 2020-10-26 6:19 ` [f2fs-dev] " Jaegeuk Kim 2020-10-26 18:47 ` asutoshd 2020-10-26 18:47 ` [f2fs-dev] " asutoshd
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