From patchwork Wed May 4 08:42:10 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Manivannan Sadhasivam X-Patchwork-Id: 569543 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2748FC433F5 for ; Wed, 4 May 2022 08:42:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1346558AbiEDIqT (ORCPT ); Wed, 4 May 2022 04:46:19 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44124 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1346544AbiEDIqS (ORCPT ); Wed, 4 May 2022 04:46:18 -0400 Received: from mail-pj1-x102a.google.com (mail-pj1-x102a.google.com [IPv6:2607:f8b0:4864:20::102a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 212DB24979 for ; Wed, 4 May 2022 01:42:34 -0700 (PDT) Received: by mail-pj1-x102a.google.com with SMTP id cx11-20020a17090afd8b00b001d9fe5965b3so4598865pjb.3 for ; Wed, 04 May 2022 01:42:34 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=/QyOJeDyGXwl5Bx88Om0rnmuC010KKBwL9CHoibu90Q=; b=uQmSVCA8Vn70bAlZqlHFGY0zK534lFsRZFsxphiKQokzX6wENHJj/OYL9o0GjLO0Yc sb6+ibl3XZ+3vMa9Gobo4vBDFQ+WtJ+sdSxkXiXPNN5wiS58S3VMU4elDLKxt+640qF4 sNPUtnUgiEx6OCsdPNuUKsFLuyK92WU9t6pATh3CMQjEkd0XNRTCkCDxyHqyEJX0PY/L KydhHkhJ+cAe8FvEiHF/xOAoWFCFLSBZ8S9vEOmN5vVHqvF3utRh/JnbwrA05sVGrlqe J7iizhbcxbXHEV+i+EuPW0Y+PasIeJrosFx5Xegz/rDPVe+Yjes+7IIHvpDk9c8bnDmS uLeA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=/QyOJeDyGXwl5Bx88Om0rnmuC010KKBwL9CHoibu90Q=; b=tG2PA3Txm+++FL8whVWsdteAoIPjfg30aMHHmi+D2tGjlep6cqStOC0e4X5GX7dHJm AisB5047T3GS1KUq3bzZgpHZ9C+lwcW7XqoqkwF0GqdSzwx4mYsaILLA6qOEr9OhOESv 6O8NWDkHmChnmiLFhQmDeq2iXsFdEptfN74vB/ix66NaxQUt8ES/9RbEtEYDGAoX5V8r wJAHyQWkF5V1hFmK4L+flNcXpDubot0pvX2J/gHNKeK+VOuid4VZyVObI9F162uPDl33 CLpcJSrnfTR064+BLhkyEXvlCk8XcP2wGIGGo2TRiJqFM5dtWOGGch8aQ4DhTq8SNRcX 5IDg== X-Gm-Message-State: AOAM532f8RRRdf/Xn+gD7P3mZUlClVA1VWAq7nQUMZo5srRKhC066+0V q3patzYqehiCMmZ4dxR5qPUO X-Google-Smtp-Source: ABdhPJzcwDo09+fKhHOOT4C79s8tTVdWNKJliXnr+1Ym042vc7sn+bwtA5HPMVxbsF79Dio5E3A3PA== X-Received: by 2002:a17:903:244e:b0:15e:b3f7:9509 with SMTP id l14-20020a170903244e00b0015eb3f79509mr8651373pls.42.1651653753809; Wed, 04 May 2022 01:42:33 -0700 (PDT) Received: from localhost.localdomain ([27.111.75.248]) by smtp.gmail.com with ESMTPSA id i10-20020a170902c94a00b0015e8d4eb278sm1386561pla.194.2022.05.04.01.42.29 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 04 May 2022 01:42:33 -0700 (PDT) From: Manivannan Sadhasivam To: martin.petersen@oracle.com, jejb@linux.ibm.com Cc: avri.altman@wdc.com, alim.akhtar@samsung.com, bjorn.andersson@linaro.org, linux-arm-msm@vger.kernel.org, quic_asutoshd@quicinc.com, quic_cang@quicinc.com, linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org, bvanassche@acm.org, ahalaney@redhat.com, Manivannan Sadhasivam , stable@vger.kernel.org Subject: [PATCH v3 3/5] scsi: ufs: qcom: Add a readl() to make sure ref_clk gets enabled Date: Wed, 4 May 2022 14:12:10 +0530 Message-Id: <20220504084212.11605-4-manivannan.sadhasivam@linaro.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20220504084212.11605-1-manivannan.sadhasivam@linaro.org> References: <20220504084212.11605-1-manivannan.sadhasivam@linaro.org> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-scsi@vger.kernel.org In ufs_qcom_dev_ref_clk_ctrl(), it was noted that the ref_clk needs to be stable for at least 1us. Even though there is wmb() to make sure the write gets "completed", there is no guarantee that the write actually reached the UFS device. There is a good chance that the write could be stored in a Write Buffer (WB). In that case, even though the CPU waits for 1us, the ref_clk might not be stable for that period. So lets do a readl() to make sure that the previous write has reached the UFS device before udelay(). Also, the wmb() after writel_relaxed is not really needed. Both writel and readl are ordered on all architectures and the CPU won't speculate instructions after readl() due to the in-built control dependency with read value on weakly ordered architectures. So it can be safely removed. Cc: stable@vger.kernel.org Fixes: f06fcc7155dc ("scsi: ufs-qcom: add QUniPro hardware support and power optimizations") Reviewed-by: Bjorn Andersson Signed-off-by: Manivannan Sadhasivam --- drivers/scsi/ufs/ufs-qcom.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/drivers/scsi/ufs/ufs-qcom.c b/drivers/scsi/ufs/ufs-qcom.c index 6126e50b9af4..b718c38fccc9 100644 --- a/drivers/scsi/ufs/ufs-qcom.c +++ b/drivers/scsi/ufs/ufs-qcom.c @@ -687,8 +687,11 @@ static void ufs_qcom_dev_ref_clk_ctrl(struct ufs_qcom_host *host, bool enable) writel_relaxed(temp, host->dev_ref_clk_ctrl_mmio); - /* ensure that ref_clk is enabled/disabled before we return */ - wmb(); + /* + * Make sure the write to ref_clk reaches the destination and + * not stored in a Write Buffer (WB). + */ + readl(host->dev_ref_clk_ctrl_mmio); /* * If we call hibern8 exit after this, we need to make sure that