From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id CCFA7C4363A for ; Mon, 26 Oct 2020 18:47:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 68C362085B for ; Mon, 26 Oct 2020 18:47:26 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=mg.codeaurora.org header.i=@mg.codeaurora.org header.b="F6WWq8qn" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1790289AbgJZSrZ (ORCPT ); Mon, 26 Oct 2020 14:47:25 -0400 Received: from m42-4.mailgun.net ([69.72.42.4]:46237 "EHLO m42-4.mailgun.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1790226AbgJZSrY (ORCPT ); Mon, 26 Oct 2020 14:47:24 -0400 DKIM-Signature: a=rsa-sha256; v=1; c=relaxed/relaxed; d=mg.codeaurora.org; q=dns/txt; s=smtp; t=1603738043; h=Message-ID: References: In-Reply-To: Subject: Cc: To: From: Date: Content-Transfer-Encoding: Content-Type: MIME-Version: Sender; bh=IuMktuI/NzJNFZzTb5UtNKt9fniQXDSsFqHN0KzCiy4=; b=F6WWq8qn7ukVx3F7/GbgO+XfR2rjAw+J8UYUvOhhF/SApQBLH08RIyzoie47moTwKV/hSkpq G8J04w7mEUIUASptHty/PzJePer29dOTDA1K+OzYaE9YowISjutcPItkuSP3NrgHe020zehn iUE0pLvSeR1vIUvgn3J0MxF6rHw= X-Mailgun-Sending-Ip: 69.72.42.4 X-Mailgun-Sid: WyI0MWYwYSIsICJsaW51eC1rZXJuZWxAdmdlci5rZXJuZWwub3JnIiwgImJlOWU0YSJd Received: from smtp.codeaurora.org (ec2-35-166-182-171.us-west-2.compute.amazonaws.com [35.166.182.171]) by smtp-out-n05.prod.us-west-2.postgun.com with SMTP id 5f9719ba0fda47b9a08edc78 (version=TLS1.2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256); Mon, 26 Oct 2020 18:47:22 GMT Sender: asutoshd=codeaurora.org@mg.codeaurora.org Received: by smtp.codeaurora.org (Postfix, from userid 1001) id CA967C43387; Mon, 26 Oct 2020 18:47:22 +0000 (UTC) Received: from mail.codeaurora.org (localhost.localdomain [127.0.0.1]) (using TLSv1 with cipher ECDHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) (Authenticated sender: asutoshd) by smtp.codeaurora.org (Postfix) with ESMTPSA id 3C9E6C433CB; Mon, 26 Oct 2020 18:47:21 +0000 (UTC) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII; format=flowed Content-Transfer-Encoding: 7bit Date: Mon, 26 Oct 2020 11:47:21 -0700 From: asutoshd@codeaurora.org To: Jaegeuk Kim Cc: Can Guo , linux-kernel@vger.kernel.org, linux-@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, kernel-team@android.com, Alim Akhtar , Avri Altman Subject: Re: [PATCH v2 5/5] scsi: ufs: fix clkgating on/off correctly In-Reply-To: <20201022201825.GA3329812@google.com> References: <20201020195258.2005605-1-jaegeuk@kernel.org> <20201020195258.2005605-6-jaegeuk@kernel.org> <2a8ecc4185b3a5411077f4e3fc66000f@codeaurora.org> <20201021045213.GB3004521@google.com> <20201022201825.GA3329812@google.com> Message-ID: X-Sender: asutoshd@codeaurora.org User-Agent: Roundcube Webmail/1.3.9 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2020-10-22 17:53, Jaegeuk Kim wrote: > On 10/21, Can Guo wrote: >> On 2020-10-21 12:52, jaegeuk@kernel.org wrote: >> > 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. >> > >> >> If clocks cannot be gated after the last task is cleared from UFS >> host, then >> clk gating >> is broken, no? Assume UFS has completed the last task in its queue, as >> this >> change says, >> ufshcd_any_tag_in_use() is preventing ufshcd_release() from invoking >> gate_work(). >> Similarly, ufshcd_any_tag_in_use() can prevent gate_work() from doing >> its >> real work - >> disabling the clocks. Do you agree? >> >> if (hba->clk_gating.active_reqs >> || hba->ufshcd_state != UFSHCD_STATE_OPERATIONAL >> || ufshcd_any_tag_in_use(hba) || >> hba->outstanding_tasks >> || hba->active_uic_cmd || hba->uic_async_done) >> goto rel_lock; > > I see the point, but this happens only when clkgate_delay_ms is too > short > to give enough time for releasing tag. If it's correctly set, I think > there'd > be no problem, unless softirq was delayed by other RT threads which is > just > a corner case tho. > >> >> Thanks, >> >> Can Guo. >> >> > > >> > > 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 >> > > > Cc: Avri Altman >> > > > Cc: Can Guo >> > > > Signed-off-by: Jaegeuk Kim >> > > > --- >> > > > 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; How about checking outstanding_reqs as well, say in ufshcd_any_tag_in_use() ? -asd From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 290F9C5517A for ; Mon, 26 Oct 2020 18:49:03 +0000 (UTC) Received: from lists.sourceforge.net (lists.sourceforge.net [216.105.38.7]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id A0DD52085B; Mon, 26 Oct 2020 18:49:02 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=sourceforge.net header.i=@sourceforge.net header.b="dtOupaA8"; 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Mon, 26 Oct 2020 18:47:23 GMT Received: by smtp.codeaurora.org (Postfix, from userid 1001) id B15A8C433FF; Mon, 26 Oct 2020 18:47:22 +0000 (UTC) Received: from mail.codeaurora.org (localhost.localdomain [127.0.0.1]) (using TLSv1 with cipher ECDHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) (Authenticated sender: asutoshd) by smtp.codeaurora.org (Postfix) with ESMTPSA id 3C9E6C433CB; Mon, 26 Oct 2020 18:47:21 +0000 (UTC) MIME-Version: 1.0 Date: Mon, 26 Oct 2020 11:47:21 -0700 From: asutoshd@codeaurora.org To: Jaegeuk Kim In-Reply-To: <20201022201825.GA3329812@google.com> References: <20201020195258.2005605-1-jaegeuk@kernel.org> <20201020195258.2005605-6-jaegeuk@kernel.org> <2a8ecc4185b3a5411077f4e3fc66000f@codeaurora.org> <20201021045213.GB3004521@google.com> <20201022201825.GA3329812@google.com> Message-ID: X-Sender: asutoshd@codeaurora.org User-Agent: Roundcube Webmail/1.3.9 X-Headers-End: 1kX7Y1-00EcEO-7u Subject: Re: [f2fs-dev] [PATCH v2 5/5] scsi: ufs: fix clkgating on/off correctly X-BeenThere: linux-f2fs-devel@lists.sourceforge.net X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-kernel@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, linux-@vger.kernel.org, Avri Altman , Can Guo , Alim Akhtar , kernel-team@android.com Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Errors-To: linux-f2fs-devel-bounces@lists.sourceforge.net On 2020-10-22 17:53, Jaegeuk Kim wrote: > On 10/21, Can Guo wrote: >> On 2020-10-21 12:52, jaegeuk@kernel.org wrote: >> > 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. >> > >> >> If clocks cannot be gated after the last task is cleared from UFS >> host, then >> clk gating >> is broken, no? Assume UFS has completed the last task in its queue, as >> this >> change says, >> ufshcd_any_tag_in_use() is preventing ufshcd_release() from invoking >> gate_work(). >> Similarly, ufshcd_any_tag_in_use() can prevent gate_work() from doing >> its >> real work - >> disabling the clocks. Do you agree? >> >> if (hba->clk_gating.active_reqs >> || hba->ufshcd_state != UFSHCD_STATE_OPERATIONAL >> || ufshcd_any_tag_in_use(hba) || >> hba->outstanding_tasks >> || hba->active_uic_cmd || hba->uic_async_done) >> goto rel_lock; > > I see the point, but this happens only when clkgate_delay_ms is too > short > to give enough time for releasing tag. If it's correctly set, I think > there'd > be no problem, unless softirq was delayed by other RT threads which is > just > a corner case tho. > >> >> Thanks, >> >> Can Guo. >> >> > > >> > > 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 >> > > > Cc: Avri Altman >> > > > Cc: Can Guo >> > > > Signed-off-by: Jaegeuk Kim >> > > > --- >> > > > 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; How about checking outstanding_reqs as well, say in ufshcd_any_tag_in_use() ? -asd _______________________________________________ Linux-f2fs-devel mailing list Linux-f2fs-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel