From patchwork Thu Dec 21 18:25:23 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andrew Halaney X-Patchwork-Id: 757408 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 E1F79768E4 for ; Thu, 21 Dec 2023 18:25:48 +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="aqFylSxv" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1703183148; 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=hFXXGAQMvAtKWxVkRcpFMTchD2fzgAOU8dNzT5bz2Wo=; b=aqFylSxv/dZsyrd41kfWDYyUHWPk5QUZa5ly9QhE/LTIyEazUzKJzoeR3QWsDJwp+C/X/i /iv5Lp6iDWxvgXwrlxpgfthzEoOgE66kuWlxk0IqhdFfjQ7QhCw5cDQGohA38Lc7h9BdLY 6Yvq3AtvZpThsYCdXceGsRv+pwq+EqE= 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-678-40JaUZ3mPz6yEsVK_ZA9CQ-1; Thu, 21 Dec 2023 13:25:46 -0500 X-MC-Unique: 40JaUZ3mPz6yEsVK_ZA9CQ-1 Received: by mail-qv1-f70.google.com with SMTP id 6a1803df08f44-67f7b69433dso16491266d6.1 for ; Thu, 21 Dec 2023 10:25:46 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1703183145; x=1703787945; h=cc:to:in-reply-to:references:message-id:content-transfer-encoding :mime-version:subject:date:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=hFXXGAQMvAtKWxVkRcpFMTchD2fzgAOU8dNzT5bz2Wo=; b=YPuPj0Ryt+Iq6tk1fuhR5fLpgupD+ANAUOf7hsd8CSolXOXqhRcgZWZg9x3hzj2yG1 hqiTMiUmpuS7Ln8rslpIHaAX/YF4ofqF6bOss/Ws9c0V1p2hcvpTLSN9rTyOKI0Cm7VP Y6XIEEPsq+mdEMpKif5QEixJNeJ+o7XPYow0cBxVmnyWkkXxb0ee+I783CUK5fWcxl0j xSD1HtDsJM3qBU/wSlAky8kA5JqG1j5r/yioUsbpg3DNRtMO4k2kJrJGDYIf8G+uB7Nk z006YZzOb3aG0ItswjDRLsciiclBd/ym1iLzvOzbQ/vNpXVdLcNVzsDLUBVCLEqiH4zM SJEw== X-Gm-Message-State: AOJu0YxlxXe0kOcL8A+DMtdJtaU9Pkg+dt3pKGGYAaGumktr24mv06Lr ZF/m/D35xF7FlcGVFElXlooL9xlrgMXbX8sgq4Ih/5/Ee1CkfuCRsq+5K+gvJcGLrcfL3rLfK7l aQqV3j1xJAdvrdlLFZn83RLSmo/ih6A== X-Received: by 2002:a05:6214:20e6:b0:67a:a721:caf4 with SMTP id 6-20020a05621420e600b0067aa721caf4mr121000qvk.85.1703183144903; Thu, 21 Dec 2023 10:25:44 -0800 (PST) X-Google-Smtp-Source: AGHT+IEIzHIP8IP+Btntq31oA+NJrP8wQlY6ZrjfmYei4CjrYTO1lr59Bq4x9PrGSfUb4jsXlwQcHw== X-Received: by 2002:a05:6214:20e6:b0:67a:a721:caf4 with SMTP id 6-20020a05621420e600b0067aa721caf4mr120983qvk.85.1703183144634; Thu, 21 Dec 2023 10:25:44 -0800 (PST) Received: from [192.168.1.163] ([2600:1700:1ff0:d0e0::37]) by smtp.gmail.com with ESMTPSA id da7-20020a05621408c700b0067f2c03d4adsm779605qvb.100.2023.12.21.10.25.41 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 21 Dec 2023 10:25:44 -0800 (PST) From: Andrew Halaney Date: Thu, 21 Dec 2023 12:25:23 -0600 Subject: [PATCH RFC v2 06/11] scsi: ufs: cdns-pltfrm: Perform read back after writing HCLKDIV Precedence: bulk X-Mailing-List: linux-scsi@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Message-Id: <20231221-ufs-reset-ensure-effect-before-delay-v2-6-75af2a9bae51@redhat.com> References: <20231221-ufs-reset-ensure-effect-before-delay-v2-0-75af2a9bae51@redhat.com> In-Reply-To: <20231221-ufs-reset-ensure-effect-before-delay-v2-0-75af2a9bae51@redhat.com> To: Andy Gross , Bjorn Andersson , Konrad Dybcio , Manivannan Sadhasivam , "James E.J. Bottomley" , "Martin K. Petersen" , Yaniv Gardi , Dov Levenglick , Hannes Reinecke , Subhash Jadavani , Gilad Broner , Venkat Gopalakrishnan , Janek Kotas , Alim Akhtar , Avri Altman , Bart Van Assche , Anjana Hari , Dolev Raviv , Can Guo Cc: Will Deacon , linux-arm-msm@vger.kernel.org, linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org, Andrew Halaney X-Mailer: b4 0.12.3 Currently, HCLKDIV is written to and then completed with an mb(). mb() ensure that the write completes, 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 mb()'s purpose wasn't to add extra ordering (on top of the ordering guaranteed by writel()/readl()), it can safely be removed. Fixes: d90996dae8e4 ("scsi: ufs: Add UFS platform driver for Cadence UFS") Signed-off-by: Andrew Halaney Reviewed-by: Manivannan Sadhasivam --- drivers/ufs/host/cdns-pltfrm.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/ufs/host/cdns-pltfrm.c b/drivers/ufs/host/cdns-pltfrm.c index bb30267da471..66811d8d1929 100644 --- a/drivers/ufs/host/cdns-pltfrm.c +++ b/drivers/ufs/host/cdns-pltfrm.c @@ -136,7 +136,7 @@ static int cdns_ufs_set_hclkdiv(struct ufs_hba *hba) * Make sure the register was updated, * UniPro layer will not work with an incorrect value. */ - mb(); + ufshcd_readl(hba, CDNS_UFS_REG_HCLKDIV); return 0; }