From patchwork Thu Dec 21 18:25:18 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andrew Halaney X-Patchwork-Id: 757838 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 594BF63503 for ; Thu, 21 Dec 2023 18:25:34 +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="F2xMDQ3H" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1703183134; 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=nPTRfp6XgPJwYrXbStNGHlrTw26cplB52DVfER92OzE=; b=F2xMDQ3H46WT9iwBqnIZQOUTVEHrKdLE3cSrkX63p4O/iaC+vjpjptKiiBxVmpWL1yQW2B +5aOR9SFrKf9WL+uo3+XddxpdBTIVF30/DUyLMtCccanzwToJYb+eoptPMB6S6DPfUv7xU 2Tp4QedwRFnE81U2qY0fyn0DZ7kXVys= Received: from mail-qv1-f70.google.com (mail-qv1-f70.google.com [209.85.219.70]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-460-iS_eTF5MNba6JKPrAPXptg-1; Thu, 21 Dec 2023 13:25:32 -0500 X-MC-Unique: iS_eTF5MNba6JKPrAPXptg-1 Received: by mail-qv1-f70.google.com with SMTP id 6a1803df08f44-67ec592bc29so15297526d6.0 for ; Thu, 21 Dec 2023 10:25:32 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1703183130; x=1703787930; 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=nPTRfp6XgPJwYrXbStNGHlrTw26cplB52DVfER92OzE=; b=wBiTw9/MSJatzJ7tMzgwWIjpFrP046O++MOrCgGaYy5xK0NqPjKNwXhZzI2rewJpqC oWTqenx2kfO/srwDw+1OsKea1Jy4pdfKB54mQzKIaNPDzJ9xNKRtuoTrxJd3qR5zfXjU I691gNL/Bv21BJKXQAy0GB8KxqBMsmtNXqLRA4+wktY6GHJM0kt/EZz6P+gDKEnWPxS1 1fa4441XtkZpc2tCxJwVuBkKvP5RevGapHMoHlgmwNCqz1yGKtPrOKm81rouE1mp5L/j NoAFaLDG2fSmKf8P0L3i0iGcwMtzvDAxu56B/bDmISrx5PXse/fHkbRG8T5hydmvSDN0 DWKg== X-Gm-Message-State: AOJu0YxgV/HDAoJR337VTlAQNmwg3PDdEBND1omiVGn9yARm3LTH8zvg kIxdDYnF/GBennPsXAcy1cIoE3yBEkPPZgXlOdLT6dMY6VBiE5wxn5A8SnnrakZIlTxKbg66Ozl P7V/dYVJMyhhnubb3oC6qVCkNcAoyOvhtKl+I94cYng== X-Received: by 2002:a05:6214:c64:b0:67f:6bd0:4943 with SMTP id t4-20020a0562140c6400b0067f6bd04943mr151781qvj.70.1703183130106; Thu, 21 Dec 2023 10:25:30 -0800 (PST) X-Google-Smtp-Source: AGHT+IEwaPbIS2XIOdrdnhMg3BXONESa5HLJNkdw6HTKr2QVRgSJuJ/M2fMoxfftCl/PZa0g5/UEVA== X-Received: by 2002:a05:6214:c64:b0:67f:6bd0:4943 with SMTP id t4-20020a0562140c6400b0067f6bd04943mr151756qvj.70.1703183129835; Thu, 21 Dec 2023 10:25:29 -0800 (PST) Received: from [192.168.1.163] ([2600:1700:1ff0:d0e0::37]) by smtp.gmail.com with ESMTPSA id da7-20020a05621408c700b0067f2c03d4adsm779605qvb.100.2023.12.21.10.25.27 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 21 Dec 2023 10:25:28 -0800 (PST) From: Andrew Halaney Date: Thu, 21 Dec 2023 12:25:18 -0600 Subject: [PATCH RFC v2 01/11] scsi: ufs: qcom: Perform read back after writing reset bit 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-v2-1-75af2a9bae51@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 , Manivannan Sadhasivam X-Mailer: b4 0.12.3 Currently, the reset bit for the UFS provided reset controller (used by its phy) is written to, and then a mb() happens to try and ensure that hit the device. Immediately afterwards a usleep_range() occurs. 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. By doing so and guaranteeing the ordering against the immediately following usleep_range(), the mb() can safely be removed. Fixes: 81c0fc51b7a7 ("ufs-qcom: add support for Qualcomm Technologies Inc platforms") Reviewed-by: Manivannan Sadhasivam Signed-off-by: Andrew Halaney --- drivers/ufs/host/ufs-qcom.h | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) diff --git a/drivers/ufs/host/ufs-qcom.h b/drivers/ufs/host/ufs-qcom.h index 9dd9a391ebb7..b9de170983c9 100644 --- a/drivers/ufs/host/ufs-qcom.h +++ b/drivers/ufs/host/ufs-qcom.h @@ -151,10 +151,10 @@ static inline void ufs_qcom_assert_reset(struct ufs_hba *hba) ufshcd_rmwl(hba, UFS_PHY_SOFT_RESET, UFS_PHY_SOFT_RESET, REG_UFS_CFG1); /* - * Make sure assertion of ufs phy reset is written to - * register before returning + * Dummy read to ensure the write takes effect before doing any sort + * of delay */ - mb(); + ufshcd_readl(hba, REG_UFS_CFG1); } static inline void ufs_qcom_deassert_reset(struct ufs_hba *hba) @@ -162,10 +162,10 @@ static inline void ufs_qcom_deassert_reset(struct ufs_hba *hba) ufshcd_rmwl(hba, UFS_PHY_SOFT_RESET, 0, REG_UFS_CFG1); /* - * Make sure de-assertion of ufs phy reset is written to - * register before returning + * Dummy read to ensure the write takes effect before doing any sort + * of delay */ - mb(); + ufshcd_readl(hba, REG_UFS_CFG1); } /* Host controller hardware version: major.minor.step */