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: 13502523 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 E97A864AAE for ; Thu, 21 Dec 2023 18:25:37 +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="UoTwTWS0" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1703183136; 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=UoTwTWS0lbXAG1PtFStjACVNiIz1QJWR7kWXLqmFXO6+3bYFPVjFJSuOkMyj4VV5MnWXyt gUa/ll/VA7zqgFC3mZP5s09FVts5s+sSv73/NLk+hB7kUT/AwG+1rR1FjlnNKlErYRafhb Vrk6FvZNwDfK72kCMoES3Tdocwy5YOw= Received: from mail-qv1-f72.google.com (mail-qv1-f72.google.com [209.85.219.72]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-187-5300JR5aO_iKBQXT_o3jKA-1; Thu, 21 Dec 2023 13:25:35 -0500 X-MC-Unique: 5300JR5aO_iKBQXT_o3jKA-1 Received: by mail-qv1-f72.google.com with SMTP id 6a1803df08f44-67ef8bbfe89so16626566d6.0 for ; Thu, 21 Dec 2023 10:25:35 -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=SOTEf0ud4aP0tUtCjuJ7ehKRMzC/VaLo+m1d+ZCP5QtU4zo8UTExc4MWcbbc8Iipqv lN5FajHOd1MYJKwe8XX+IEFTh5vLXcsrh78tWpNnXfw8mFPON0BC9mEsIq4rLkRP2KHV 1RE7v/VJmit6iujSpO6LxYii7KZ+b6OlCSzGI/OS2vHYVN3+jGkUlLsbQsQ6Svs2zhBS BJ+tIlNUqahpW63PBjyMwu4Vn5U3HvpxDhLJmr5hd48MT52lz+0+SPFhrrsAsSoCdmip rU0axtd5hf+OMZHoWB40I4AupygnhBbC0ac5cp2FGNIbykGi4BzIX7INvvJSmmqKDKt+ yI9g== X-Gm-Message-State: AOJu0YydLE1t3bz3yPqC+7WaVL/SknhGii25PjjTiBV63l0fExVC24Ss firp7CaNEyT8kAANnWqBguRsyR8M01QGwkkhGJqg8rzq95HYEDmqgbJs5baqwdmBHCtzgiuRrlS 9pC4E63T5+RaHIQMZ5BoWFj3SoWxZ2A== X-Received: by 2002:a05:6214:1948:b0:67c:d2fd:3e3f with SMTP id q8-20020a056214194800b0067cd2fd3e3fmr172135qvk.27.1703183134905; 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-scsi@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;