From patchwork Thu Dec 21 19:09:48 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andrew Halaney X-Patchwork-Id: 757405 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 4656A73182 for ; Thu, 21 Dec 2023 19:10:40 +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="hGuIszF5" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1703185840; 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=hGuIszF5ZZgnsW3OOMT0vrZFJ609xnQR5GHxXhpDpDImsgh6AJz7KOniVG8EY0omWToPc2 3f6Y6JeoBnD/te85R3mTupqzT6L8SKLtfjAvu/C71c0080ET/zi6uTOrnjz+DzpVIsgyf9 ZQHurXYzkZ2iT4RcOMI0BbUEI3ZXNBY= Received: from mail-qk1-f198.google.com (mail-qk1-f198.google.com [209.85.222.198]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-510-ALx3xI1_O7u7RkwHLYoyNQ-1; Thu, 21 Dec 2023 14:10:38 -0500 X-MC-Unique: ALx3xI1_O7u7RkwHLYoyNQ-1 Received: by mail-qk1-f198.google.com with SMTP id af79cd13be357-7811e34e9d4so89945785a.3 for ; Thu, 21 Dec 2023 11:10:38 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1703185835; x=1703790635; 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=V5DIcTT5Lroakb0MY1T0EdVJKAtxjaPCe5FVxbyPj6I=; b=YiCiTVdj9x2SYZevjdwPeTU2odtesp2w79aIrgU3vA6UCNNXHoGaoqPec7wuyF8RpO FyBBg2APFuLGKVjb3dkPgrAStVqkMm9Pw1TIhcLBUsPeYfprnI/CwdFQOO/edoLN8Y0B n+4bu26hGCv+58ZHJPw60JRh7GpnwteD4tTEeEI/I4vCCMQfLfrnqKqrPGHSZg/5Y4ky aDJM/kGQNVT8dNYK0qVFQbTPuyGBJ32fTbb+lpHhufpQKvXKImtWpBCKU5lMWCv0LQfK StD9/G4W+AplX5auQNdJpN7l2zkvFGr9tDet4vtVmRsDvwQBKPxhcjIcnaAgPvxbfSBY wnlw== X-Gm-Message-State: AOJu0Yxo3mIFSBCoJ2tBdrX97jOQuqzUYHPGxECewMozydJTtAyEgw8M KKLUEhVHutoppiK04GGdpBGuN7BGk6hfvXKd+CQlByjFjog4lSGfl7qsAf82kf1M29eg4rZiiZy J+JHV4lHBxd50upJ+zE13fNjyKxgI7Q== X-Received: by 2002:a05:620a:ed0:b0:77e:fba3:a799 with SMTP id x16-20020a05620a0ed000b0077efba3a799mr242440qkm.119.1703185835163; Thu, 21 Dec 2023 11:10:35 -0800 (PST) X-Google-Smtp-Source: AGHT+IFS+oPxyve51zvVte/ZBKV14CQT1Ccn6OrbcUqVZrbK82UWo0e9oMDiIDekfpn18HkqUsfhdA== X-Received: by 2002:a05:620a:ed0:b0:77e:fba3:a799 with SMTP id x16-20020a05620a0ed000b0077efba3a799mr242430qkm.119.1703185834841; Thu, 21 Dec 2023 11:10:34 -0800 (PST) Received: from fedora.redhat.com ([2600:1700:1ff0:d0e0::37]) by smtp.gmail.com with ESMTPSA id 25-20020a05620a04d900b0077f0a4bd3c6sm846370qks.77.2023.12.21.11.10.33 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 21 Dec 2023 11:10:34 -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 02/11] scsi: ufs: qcom: Perform read back after writing REG_UFS_SYS1CLK_1US Date: Thu, 21 Dec 2023 13:09:48 -0600 Message-ID: <20231221-ufs-reset-ensure-effect-before-delay-v3-2-2195a1b66d2e@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 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;