From patchwork Fri Mar 29 20:46:52 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andrew Halaney X-Patchwork-Id: 784398 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 899B913AD38 for ; Fri, 29 Mar 2024 20:50:49 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1711745451; cv=none; b=beytFl0kTk6hGkTM9iEbmrrv/wXZg7nAXWyFAGcVlYCPsj3bNFqw8AootArCazkbfztbAE4kD/seUXGO97i4pXKCvHFyNy8Qq8KazCtKYBlHJKz6Cm2e1ArGMZSy8hcsfuQAuGtBTSP9XzUhXb1amO2JADqU4BRg3MU0q00smyY= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1711745451; c=relaxed/simple; bh=Zy+bgvSnjLkgq0s4C6zNdmvBRZh1cOH+2n6Swd6Xvls=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=mLA0cZhG+QXPXO+Y5awDl/h4ezUJxjtxL0Aswbp3mctrhMXITbn4gdP+8Liz0F2xr71xzVR3uDcoji5egAQ8wsXSfqC6fyXz14h5drLixvu84u4JTe5u+vymL4DWMdW9olZbN+39bWauhQalqvaR7yLMGrAvm4dLbkHQDAat0lE= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=ckrvrsME; arc=none smtp.client-ip=170.10.133.124 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="ckrvrsME" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1711745448; 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=XPnsustGT4GoUrGTcO/hGoT1b1FUZsTVit4gdTDovY0=; b=ckrvrsMED1h4VCxfnb0ekQzIHI3IiRBdwKT+f6jfs2L0ilDK2Nudf4xEgo0mWeKenCPTcW 0mUzgoUGZRNuBXqX7s06aE9JeE9zsF1uUya5+mdGVx0LxICsY43ye/eBYtXbvXDMJKGgvb FMO+B9jZlCvHTdSkA2xJLRc9HYT2edk= Received: from mail-qv1-f70.google.com (mail-qv1-f70.google.com [209.85.219.70]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-322-sIFnOJscP22zvaz7q82iWg-1; Fri, 29 Mar 2024 16:50:47 -0400 X-MC-Unique: sIFnOJscP22zvaz7q82iWg-1 Received: by mail-qv1-f70.google.com with SMTP id 6a1803df08f44-69655dbec66so23874016d6.3 for ; Fri, 29 Mar 2024 13:50:47 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1711745443; x=1712350243; 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=XPnsustGT4GoUrGTcO/hGoT1b1FUZsTVit4gdTDovY0=; b=uwnhQErkuOwgPIYI+HprFS1lb9W3Hk9f9ibq9Pme67cV30o93UiQ/1m76MfjoSJGYo 7nnQR3rIhtQjqUikf/mHkGIlzQKcn2oRsSSDpPAErFQmiGlJCwWp8b/W6+xER/cI7HSo anF6klV0JODf+Bf9MGock09nejaYG14NcuXWU3HdsRclofk4I0hlqPU3WTf06XAQ6elV bJm4hAder/Up0IuGsk5r+jQZ8V0Xg1oGnELDR2rO91Byc9LcKVIQvWFk3LK0diXSwbMy 9s/kAhjuBBHKGA1pVb9ry1pAjTYKlpfplDknOVrZO490pD43bsaKlY4KWlvH9yR3NSAL MVwA== X-Forwarded-Encrypted: i=1; AJvYcCXbbDu12lFvE8IXwcN9ew6g+Uq3XdTWFMPo5zo/UGPWYW0PcJey12fCercC6K26V7dgBaXwBDVHMwJuCXABxOAEhk5dDC8OvfR8eQ== X-Gm-Message-State: AOJu0YxItiOFVspqQRt5496PbKvnfIF7ezXiAW7V5i/irmziLXFDhLYq 2k5XVZrvli6JJaqCpFdKWph5Q1BQOZ0zF/BjXZVrnJaLpg8TOfdZntfHZnXlDKvZ2lOrjKEBUTx cvroSmggNlGjLAc8HpluHmTD1mIF66rhz3UpyySziUSshzAk3+1+idORfVsw= X-Received: by 2002:a0c:d646:0:b0:698:f3f0:39dd with SMTP id e6-20020a0cd646000000b00698f3f039ddmr2065508qvj.6.1711745443262; Fri, 29 Mar 2024 13:50:43 -0700 (PDT) X-Google-Smtp-Source: AGHT+IFBLrn+K4mLNtCh2Rz2Xmh067Hv24Kl9mQ40ZdwbQbhkZQb5T0j5S5g1FGjMUP56UzrNARqQA== X-Received: by 2002:a0c:d646:0:b0:698:f3f0:39dd with SMTP id e6-20020a0cd646000000b00698f3f039ddmr2065487qvj.6.1711745442848; Fri, 29 Mar 2024 13:50:42 -0700 (PDT) Received: from x1gen2nano.redhat.com ([2600:1700:1ff0:d0e0::33]) by smtp.gmail.com with ESMTPSA id jz10-20020a0562140e6a00b00698f27c6460sm794271qvb.110.2024.03.29.13.50.38 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 29 Mar 2024 13:50:39 -0700 (PDT) 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 , Anjana Hari Cc: Andrew Halaney , Will Deacon , linux-arm-msm@vger.kernel.org, linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v5 10/11] scsi: ufs: core: Remove unnecessary wmb() after ringing doorbell Date: Fri, 29 Mar 2024 15:46:52 -0500 Message-ID: <20240329-ufs-reset-ensure-effect-before-delay-v5-10-181252004586@redhat.com> X-Mailer: git-send-email 2.44.0 In-Reply-To: <20240329-ufs-reset-ensure-effect-before-delay-v5-0-181252004586@redhat.com> References: <20240329-ufs-reset-ensure-effect-before-delay-v5-0-181252004586@redhat.com> Precedence: bulk X-Mailing-List: linux-scsi@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Mailer: b4 0.13.0 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 But, completion and taking effect aren't necessary to guarantee here. There's already other examples of the doorbell being rung that don't do this. The writel() of the doorbell guarantees prior writes by this thread (to the request being setup for example) complete prior to the ringing of the doorbell, and the following wait_for_completion_io_timeout() doesn't require any special memory barriers either. With that in mind, just remove the wmb() altogether here. Fixes: ad1a1b9cd67a ("scsi: ufs: commit descriptors before setting the doorbell") Signed-off-by: Andrew Halaney Reviewed-by: Manivannan Sadhasivam --- drivers/ufs/core/ufshcd.c | 3 --- 1 file changed, 3 deletions(-) diff --git a/drivers/ufs/core/ufshcd.c b/drivers/ufs/core/ufshcd.c index dfa4f827766a..a2f2941450fd 100644 --- a/drivers/ufs/core/ufshcd.c +++ b/drivers/ufs/core/ufshcd.c @@ -7090,10 +7090,7 @@ static int __ufshcd_issue_tm_cmd(struct ufs_hba *hba, /* send command to the controller */ __set_bit(task_tag, &hba->outstanding_tasks); - ufshcd_writel(hba, 1 << task_tag, REG_UTP_TASK_REQ_DOOR_BELL); - /* Make sure that doorbell is committed immediately */ - wmb(); spin_unlock_irqrestore(host->host_lock, flags);