From patchwork Thu Dec 21 19:09:56 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andrew Halaney X-Patchwork-Id: 13502570 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B6E0273185 for ; Thu, 21 Dec 2023 19:11:22 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="O0lZSpfa" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1703185881; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=myeBTw3HbDC/jUy61nVcNVpXoHTTT3lUStj2mtls9rs=; b=O0lZSpfa2k78TauSXiwFp5aTzC/omNqPAABJnCUiy8vYM/U3Iuzb8IHMGGWr2h4QjL1JEt 7pBM75jf5aAOLTkkTVDtN+hTw29TfGXlKAoGCULwZ521qMecoW3Py1MsSg9JOCuFLpo0jI Btb5gHku6+jrIY5sAvBUZvi3ySS7HD4= Received: from mail-qt1-f198.google.com (mail-qt1-f198.google.com [209.85.160.198]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-404-iGuLyvb7P3uSwjOptDOrjw-1; Thu, 21 Dec 2023 14:11:20 -0500 X-MC-Unique: iGuLyvb7P3uSwjOptDOrjw-1 Received: by mail-qt1-f198.google.com with SMTP id d75a77b69052e-425a6272642so16668771cf.3 for ; Thu, 21 Dec 2023 11:11:20 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1703185877; x=1703790677; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=myeBTw3HbDC/jUy61nVcNVpXoHTTT3lUStj2mtls9rs=; b=LWeAUikRUP3xtxzAPx/IF22ccBqNvSsJ6/lw5KvjbV6KtFh3OWKe6DOLnoagPDyN90 lyR4UL1XVQCNKx9oA9k+KCaL2Ui4n8KMSVNE+pW7FDpHfL5wW9116SMwjfl3p1FHbfe2 uW8YT3IIzK2ehDb+4eI6dgkOmGMM0Ey+rIpSwOUj0n4OFTEiaMMrrnglPspE/k1Jpg61 bWbnIzrpfpzArRABNcKY0hf2DR4HZ9IJ4mzsnBl8nkJNAttQnRn5Hwe7jIA6qLK03WlA pp7ifNEKiD5U4hZMej25YvTorHRwYBO5rgiYr3rXlLl+0Ir9yvUX4BJAx0/PBM4On6yi IX+w== X-Gm-Message-State: AOJu0YxUVe4JEzs9h85IO9o7zi0lKo8Ur06YnOQq0uEXGiixKZ6iDSbN xk6ppAMQn1EFnaNIYadvJTYeK6wkAg0MIs74jnIZQqG4qquu2IEfwZaHc/SelG5Xijmp7nfA+fd 8FdlM7bvhAuFN5s5zdHC+SGrSM2Qbv21pZQ== X-Received: by 2002:a05:620a:2101:b0:771:31c:adcb with SMTP id l1-20020a05620a210100b00771031cadcbmr301249qkl.7.1703185876790; Thu, 21 Dec 2023 11:11:16 -0800 (PST) X-Google-Smtp-Source: AGHT+IFIo9rP/exgPUX1MrFBn+AOlJuIaIUzWQyH80yOwSzRQUWXH5SWjG9NIk+MB93joiIr8Pn1SQ== X-Received: by 2002:a05:620a:2101:b0:771:31c:adcb with SMTP id l1-20020a05620a210100b00771031cadcbmr301230qkl.7.1703185876561; Thu, 21 Dec 2023 11:11:16 -0800 (PST) Received: from fedora.redhat.com ([2600:1700:1ff0:d0e0::37]) by smtp.gmail.com with ESMTPSA id 25-20020a05620a04d900b0077f0a4bd3c6sm846370qks.77.2023.12.21.11.11.14 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 21 Dec 2023 11:11:15 -0800 (PST) From: Andrew Halaney To: Andy Gross , Bjorn Andersson , Konrad Dybcio , Manivannan Sadhasivam , "James E.J. Bottomley" , "Martin K. Petersen" , Hannes Reinecke , Janek Kotas , Alim Akhtar , Avri Altman , Bart Van Assche , Can Guo Cc: Andrew Halaney , Will Deacon , linux-arm-msm@vger.kernel.org, linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH RFC v3 10/11] scsi: ufs: core: Perform read back to commit doorbell Date: Thu, 21 Dec 2023 13:09:56 -0600 Message-ID: <20231221-ufs-reset-ensure-effect-before-delay-v3-10-2195a1b66d2e@redhat.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20231221-ufs-reset-ensure-effect-before-delay-v3-0-2195a1b66d2e@redhat.com> References: <20231221-ufs-reset-ensure-effect-before-delay-v3-0-2195a1b66d2e@redhat.com> Precedence: bulk X-Mailing-List: linux-arm-msm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Mailer: b4 0.12.3 Currently, the doorbell is written to and a wmb() is used to commit it immediately. wmb() ensures that the write completes before following writes occur, but completion doesn't mean that it isn't stored in a buffer somewhere. The recommendation for ensuring this bit has taken effect on the device is to perform a read back to force it to make it all the way to the device. This is documented in device-io.rst and a talk by Will Deacon on this can be seen over here: https://youtu.be/i6DayghhA8Q?si=MiyxB5cKJXSaoc01&t=1678 Let's do that to ensure the bit hits the device. Because the wmb()'s purpose wasn't to add extra ordering (on top of the ordering guaranteed by writel()/readl()), it can safely be removed. Fixes: ad1a1b9cd67a ("scsi: ufs: commit descriptors before setting the doorbell") Signed-off-by: Andrew Halaney Reviewed-by: Can Guo Reviewed-by: Manivannan Sadhasivam --- drivers/ufs/core/ufshcd.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/ufs/core/ufshcd.c b/drivers/ufs/core/ufshcd.c index 75a03ee9a1ba..caebd589e08c 100644 --- a/drivers/ufs/core/ufshcd.c +++ b/drivers/ufs/core/ufshcd.c @@ -7050,7 +7050,7 @@ static int __ufshcd_issue_tm_cmd(struct ufs_hba *hba, ufshcd_writel(hba, 1 << task_tag, REG_UTP_TASK_REQ_DOOR_BELL); /* Make sure that doorbell is committed immediately */ - wmb(); + ufshcd_readl(hba, REG_UTP_TASK_REQ_DOOR_BELL); spin_unlock_irqrestore(host->host_lock, flags);