From patchwork Thu Dec 21 19:09:51 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andrew Halaney X-Patchwork-Id: 13502577 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 BFD887691A for ; Thu, 21 Dec 2023 19:10:56 +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="gY4edpsD" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1703185855; 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=oX0CWwSSb/xcfXKSUEFguRgCx8LqXafuU1W5XbBtf6I=; b=gY4edpsDhHnwH+l/JQ3iK08HKdl26Z5WHFyRyiXRmRxnEQ9FD5i6zeQAoGjq4l6xBG8Rd8 Ka2DmaY9g1El1l/YHch05wWSZ8Cdn7tAz0fecDqr4RibUQbT2+xSdOobKtHhcxHB/pRZkO ZRz55o9/c9WKGNTpiuEWQokSNsXOReE= 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-479-pWtqZU1eO1i7JbXMm3QPMg-1; Thu, 21 Dec 2023 14:10:54 -0500 X-MC-Unique: pWtqZU1eO1i7JbXMm3QPMg-1 Received: by mail-qk1-f198.google.com with SMTP id af79cd13be357-7810802421bso135538585a.2 for ; Thu, 21 Dec 2023 11:10:54 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1703185850; x=1703790650; 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=oX0CWwSSb/xcfXKSUEFguRgCx8LqXafuU1W5XbBtf6I=; b=ucFMXcMwjxsbf8t/mgDeBkQcpotRsvpeX2dCFZJb8lPWLtR8omm5+y2BNQ50VYMwYq zxC1K8YMzz2EtKjED16OZoRvoMeGhyIjPJy+mYxwqgRrO2hm6X/DulHXxEJLKSwwCtsY K0l+5A9sugab86OsHBjEd3//sOaxpO4QicpDMul29CUx0vL9U6hydfLtV7C1YNCk+Htd /+FtM89WBA5slm51eLjDGM+ePWjnJa+EPKKWLJ8PJD55otGUVSefdGj2QFxLxNgBvQ43 tfjza7TZuqQsyS8p5S4U8ChqCZ3NxayiTBpv1Q5zbyHXVtlzSwhZ9ZHwXMY/zykiTu3+ STpg== X-Gm-Message-State: AOJu0YyeaHC6fbM7gVPWCekm3X0eHXBKY1XGHS8DWD6ee9Pv+kQfRV9F vEu6FRleDvCIoMQtqou2DXvSbKTsysRiwEKd8oEPtiMSAvnbIwONuOwIyfLHXvx3l2k4/omKask x5xbYNjFEAY25yhainAprF5jab8JccA== X-Received: by 2002:a05:620a:2914:b0:77f:92f:fcc0 with SMTP id m20-20020a05620a291400b0077f092ffcc0mr328952qkp.24.1703185850248; Thu, 21 Dec 2023 11:10:50 -0800 (PST) X-Google-Smtp-Source: AGHT+IGFFmVes4XMCZ3lGbcjd+Jg+rBUmhWnl7+B+n29gnbBYnepEnbM62uIlen/a5SDWSV96Vlghg== X-Received: by 2002:a05:620a:2914:b0:77f:92f:fcc0 with SMTP id m20-20020a05620a291400b0077f092ffcc0mr328927qkp.24.1703185849959; Thu, 21 Dec 2023 11:10:49 -0800 (PST) Received: from fedora.redhat.com ([2600:1700:1ff0:d0e0::37]) by smtp.gmail.com with ESMTPSA id 25-20020a05620a04d900b0077f0a4bd3c6sm846370qks.77.2023.12.21.11.10.47 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 21 Dec 2023 11:10:48 -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 05/11] scsi: ufs: qcom: Perform read back after writing CGC enable Date: Thu, 21 Dec 2023 13:09:51 -0600 Message-ID: <20231221-ufs-reset-ensure-effect-before-delay-v3-5-2195a1b66d2e@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, the CGC enable bit is written and then an mb() is used to ensure that completes before continuing. 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: 81c0fc51b7a7 ("ufs-qcom: add support for Qualcomm Technologies Inc platforms") Signed-off-by: Andrew Halaney Reviewed-by: Can Guo --- 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 ab1ff7432d11..3db19591d008 100644 --- a/drivers/ufs/host/ufs-qcom.c +++ b/drivers/ufs/host/ufs-qcom.c @@ -409,7 +409,7 @@ static void ufs_qcom_enable_hw_clk_gating(struct ufs_hba *hba) REG_UFS_CFG2); /* Ensure that HW clock gating is enabled before next operations */ - mb(); + ufshcd_readl(hba, REG_UFS_CFG2); } static int ufs_qcom_hce_enable_notify(struct ufs_hba *hba,