From patchwork Thu Dec 21 18:25:19 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andrew Halaney X-Patchwork-Id: 13502515 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (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 9884E651BA for ; Thu, 21 Dec 2023 18:25:41 +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="jLUehBxQ" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1703183140; 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=V5DIcTT5Lroakb0MY1T0EdVJKAtxjaPCe5FVxbyPj6I=; b=jLUehBxQqG1coO39PQfO+uU4Q86oTbOBPk6BlZVm09f86PJXodxKayHNi0s/nPk/Vxwqui T/n/N+AAh9yJpzFcFV7hoaG6PnJlIMiRw6VpuPylQyx/ZpavpUP1fMdAPULFAASMcP5t8M V0wjtiMxRQIpm6XptovLT07/W7O4V0s= Received: from mail-qv1-f71.google.com (mail-qv1-f71.google.com [209.85.219.71]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-503-UTxuSEcRM_mW3KxccKR6Vg-1; Thu, 21 Dec 2023 13:25:39 -0500 X-MC-Unique: UTxuSEcRM_mW3KxccKR6Vg-1 Received: by mail-qv1-f71.google.com with SMTP id 6a1803df08f44-67eee3fbeb1so16441206d6.2 for ; Thu, 21 Dec 2023 10:25:39 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1703183135; x=1703787935; 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=V5DIcTT5Lroakb0MY1T0EdVJKAtxjaPCe5FVxbyPj6I=; b=Y6pV5oHokZSQYnXCk+9pKOycwcr4YhTvwHhC+u7uSTwif7vrKFjrnCPWh3ZMDULAbD 0CO6QEFpUfIzgj/2HEYM4t26vWGuYG+5HsFR0LUluk5SsIcqDMD9ml1SrzNImxPrqHgV x6mMt/hQRww+ZrdXaIGKeBHkPvHHvKZF3I1uV8VMIWfuV3ZLXI5TMGD0cilfJg3qp1uv zgv4W3siWl1gDH8OdFfTnwPYDrW3v8+mLyyiM/laI7USbAp9gj880vx0ty5UangEQC5H 3n8V8lXBLY63QghKVI8UML7nCfvfH5yytaglvqddFw7ixcB6W4h2lb+rrZZtTnvSHARV 1krg== X-Gm-Message-State: AOJu0Ywk2R3B0Ky8MvfPUBapZ161nW47ykChQhsxd6xqgWCy4fGGPDXk S/ybfd621CP6tQA3MiNLZCv8h5S+kCmDsCj6+jCMaDAyWDFDKZZoPAfv9lTSwqlxRinCOF9+Sqf CgkBEg3F8K3vllaDL7Fxck1fEq9ME2Kznug== X-Received: by 2002:a05:6214:1948:b0:67c:d2fd:3e3f with SMTP id q8-20020a056214194800b0067cd2fd3e3fmr172125qvk.27.1703183134899; Thu, 21 Dec 2023 10:25:34 -0800 (PST) X-Google-Smtp-Source: AGHT+IHpc21i8CXWcL7uGVYN0nuNkhKxkO1wr9OVN8ezMhEFu/TuLI+a1iHq3RjIIe+4CssICPiVQw== X-Received: by 2002:a05:6214:1948:b0:67c:d2fd:3e3f with SMTP id q8-20020a056214194800b0067cd2fd3e3fmr172113qvk.27.1703183134657; Thu, 21 Dec 2023 10:25:34 -0800 (PST) Received: from [192.168.1.163] ([2600:1700:1ff0:d0e0::37]) by smtp.gmail.com with ESMTPSA id da7-20020a05621408c700b0067f2c03d4adsm779605qvb.100.2023.12.21.10.25.29 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 21 Dec 2023 10:25:30 -0800 (PST) From: Andrew Halaney Date: Thu, 21 Dec 2023 12:25:19 -0600 Subject: [PATCH RFC v2 02/11] scsi: ufs: qcom: Perform read back after writing REG_UFS_SYS1CLK_1US Precedence: bulk X-Mailing-List: linux-arm-msm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Message-Id: <20231221-ufs-reset-ensure-effect-before-delay-v2-2-75af2a9bae51@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 after writing to REG_UFS_SYS1CLK_1US a mb() is used to ensure that write has gone through to the device. 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: f06fcc7155dc ("scsi: ufs-qcom: add QUniPro hardware support and power optimizations") Signed-off-by: Andrew Halaney --- drivers/ufs/host/ufs-qcom.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/ufs/host/ufs-qcom.c b/drivers/ufs/host/ufs-qcom.c index 480787048e75..4c15c8a1d058 100644 --- a/drivers/ufs/host/ufs-qcom.c +++ b/drivers/ufs/host/ufs-qcom.c @@ -501,7 +501,7 @@ static int ufs_qcom_cfg_timers(struct ufs_hba *hba, u32 gear, * make sure above write gets applied before we return from * this function. */ - mb(); + ufshcd_readl(hba, REG_UFS_SYS1CLK_1US); } return 0;