From patchwork Thu Dec 21 19:09:52 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andrew Halaney X-Patchwork-Id: 757403 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 0628076DDC for ; Thu, 21 Dec 2023 19:11:02 +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="HkhBywOr" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1703185861; 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=HkhBywOrTeQdnchFaeVrUdxorUkUnxr5nX4/6yGhDueM55bl0RMUYNSIasrI6Is39ondUg aVYlIDxML81Jb3xaWbEKPYVKOnq+71AIqMv6Flpiw4E0U0F4L1kW8LB7vabL6tSBmylPI9 +Pf1NU2daFrY0eHt288tbmZa24t5E1s= Received: from mail-qk1-f200.google.com (mail-qk1-f200.google.com [209.85.222.200]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-634-0NmbFfoAO9CH1LkHU_c25A-1; Thu, 21 Dec 2023 14:10:59 -0500 X-MC-Unique: 0NmbFfoAO9CH1LkHU_c25A-1 Received: by mail-qk1-f200.google.com with SMTP id af79cd13be357-7812a544766so14878385a.1 for ; Thu, 21 Dec 2023 11:10:59 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1703185855; x=1703790655; 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=hFXXGAQMvAtKWxVkRcpFMTchD2fzgAOU8dNzT5bz2Wo=; b=DnR59PAxd9v9nz8X0A8vNTV/ctkvrhkb4sR189T8wuM/QfiH8Pi8F57wNbMiwWV6wI DawS8qKpe0B33ql0elGDwQTGIBUBXDymm+ZEYQVELtjLcC1cSiHuITARIrPu4vAQev9P HekAuXYtouM2/PQz2GRQLQgygcdCCxyMGAm2ckS1ISE87FU/RRsdm2i78fRDiUZbtyU/ dK67GNYpbS6v1ULdc0G727bX2vjnvaIeJDwpIYvK8hWMSUHDvjSBRnjikaDClVOuVJGc cmV9xDzSA7aEDhtK/AJSDrzWWqN9mUIEe5XEMhPXHjvm4SW+02EtDnmOzHpRefixu5QH pNww== X-Gm-Message-State: AOJu0Yy/+cykAO3AYQXtkGZIEN1ag0DT8UiQRPx0gLyRlIAIaHJcfkZ5 Rpa3l6jrJCkGknUBwuhRo2+bdAL6bXmJecSn5DKNsv9ibzVn5YMEJAUnVGtuN3gWLyZaSR+lY1g 3ZL+pa6xj9fVsq+6Tj6pU/0sMpS7gqg== X-Received: by 2002:a37:c40c:0:b0:781:1c42:5d90 with SMTP id d12-20020a37c40c000000b007811c425d90mr241285qki.132.1703185854952; Thu, 21 Dec 2023 11:10:54 -0800 (PST) X-Google-Smtp-Source: AGHT+IH41P8+ouBveiK5K1CSO/CoPmnxClgg8ifdygVCzqdRtytdGED2eAZr0tztRiLQw8uOEhQXcA== X-Received: by 2002:a37:c40c:0:b0:781:1c42:5d90 with SMTP id d12-20020a37c40c000000b007811c425d90mr241267qki.132.1703185854718; Thu, 21 Dec 2023 11:10:54 -0800 (PST) Received: from fedora.redhat.com ([2600:1700:1ff0:d0e0::37]) by smtp.gmail.com with ESMTPSA id 25-20020a05620a04d900b0077f0a4bd3c6sm846370qks.77.2023.12.21.11.10.51 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 21 Dec 2023 11:10:52 -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 06/11] scsi: ufs: cdns-pltfrm: Perform read back after writing HCLKDIV Date: Thu, 21 Dec 2023 13:09:52 -0600 Message-ID: <20231221-ufs-reset-ensure-effect-before-delay-v3-6-2195a1b66d2e@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-scsi@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 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 --- 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; }