From patchwork Thu Dec 21 19:09:46 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andrew Halaney X-Patchwork-Id: 13502572 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 7F34665189 for ; Thu, 21 Dec 2023 19:10:23 +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="ggAMIjjD" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1703185822; 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; bh=hZHuvhwToeaoaoZVXmPZHHVtGh/nwSUb0e8gt0f15YM=; b=ggAMIjjDAaxx2XQc9dOfePMgZ0Xk5ovMVc1qCT57I+5mXYkUrcZwlodjxkSa+W7zNBPM41 3XYpBtWemht/FP2i98tVK9P2YXH9r+qCCNveUEPmXccQZERg/cc6KnWHIoPrL1LVo8iLTH xxKSEQD88U+0TKJJHNnifG0Y+4BlqCk= Received: from mail-qt1-f198.google.com (mail-qt1-f198.google.com [209.85.160.198]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-178-V3bXisuSPNGjyqjyR3Ey8w-1; Thu, 21 Dec 2023 14:10:20 -0500 X-MC-Unique: V3bXisuSPNGjyqjyR3Ey8w-1 Received: by mail-qt1-f198.google.com with SMTP id d75a77b69052e-4277cd01468so15811811cf.3 for ; Thu, 21 Dec 2023 11:10:20 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1703185820; x=1703790620; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=hZHuvhwToeaoaoZVXmPZHHVtGh/nwSUb0e8gt0f15YM=; b=XsrpZblJLM89O4NYw8b7ooekjbwqYQMHuAPa2ymGTrToQM/R97/drhW8KXaV8GQ/uv 6l5+kOu/EY0WFCQZJnX9hvJxx6LsG9iYXhhvwZjaIBGy0/dRYp7Quh8k+c8FadzuWHLu UYelQ5tWEklLX/GTa59X40O97RWpHyuxjaGaub9IZtl3zfC9jsatOBwKNeH/T8b/lcW1 F/LmADGLkLRUauKRNxdAzk+LIjBgComEmAyDfAg7rCjo4qFsf9Gd7MAgdMswrsbMyV7x idEeCwxnNwUGxkB5wY2VHWgyou/uhFhTWOMGUXfdf3J10tVyE7aZ+Pe9tc0Jtw8ctnla gjgA== X-Gm-Message-State: AOJu0YxOtcef5XFDLajHJCZVwK64/F2wmsumu28huG3lWn5NsxRQy1mP 29W865wUvAJQswfan8kYKaVdXtiWoEGZQPQIjJAvOC0tE2W4HYPOgVSRIEH9uq+ZLTWXe8qPzwJ 4J7ugInRrfp4co69Sm74oXRaNiUe6HA== X-Received: by 2002:a05:6214:f27:b0:67f:f92:29ff with SMTP id iw7-20020a0562140f2700b0067f0f9229ffmr171527qvb.123.1703185819859; Thu, 21 Dec 2023 11:10:19 -0800 (PST) X-Google-Smtp-Source: AGHT+IGx2O2/q9nQgS6+PqwWNkUib41xKh58crZQWBXyWSQ3d0w0skt4cmacBiYQUg7/dkT6UrakvQ== X-Received: by 2002:a05:6214:f27:b0:67f:f92:29ff with SMTP id iw7-20020a0562140f2700b0067f0f9229ffmr171513qvb.123.1703185819605; Thu, 21 Dec 2023 11:10:19 -0800 (PST) Received: from fedora.redhat.com ([2600:1700:1ff0:d0e0::37]) by smtp.gmail.com with ESMTPSA id 25-20020a05620a04d900b0077f0a4bd3c6sm846370qks.77.2023.12.21.11.10.18 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 21 Dec 2023 11:10:19 -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 00/11] scsi: ufs: Remove overzealous memory barriers Date: Thu, 21 Dec 2023 13:09:46 -0600 Message-ID: <20231221-ufs-reset-ensure-effect-before-delay-v3-0-2195a1b66d2e@redhat.com> X-Mailer: git-send-email 2.43.0 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 This is an RFC because I'm not all the confident in this topic. UFS has a lot of mb() variants used, most with comments saying "ensure this takes effect before continuing". mb()'s aren't really the way to guarantee that, a read back is the best method. Some of these though I think could go a step further and remove the mb() variant without a read back. As far as I can tell there's no real reason to ensure it takes effect in most cases (there's no delay() or anything afterwards, and eventually another readl()/writel() happens which is by definition ordered). In this current series I don't do that as I wasn't totally convinced, but it should be considered when reviewing. Hopefully this series gets enough interest where we can confidently merge the final result after review helps improve it. I'll be travelling a good bit the next 2ish weeks, so expect little response until my return. Thanks in advance for the help, Andrew Signed-off-by: Andrew Halaney --- Changes in v3: - Nothing changed, I just failed to send with b4 (resulting in 2 half sent v2 series on list) - Link to v2: https://lore.kernel.org/r/pnwsdz3i2liivjxvtfwq6tijotgh5adyqipjjb5wdvo4jpu7yv@j6fkshm5ipue Changes in v2: - Added review tags for original patch - Added new patches to address all other memory barriers used - Link to v1: https://lore.kernel.org/r/20231208-ufs-reset-ensure-effect-before-delay-v1-1-8a0f82d7a09e@redhat.com --- Andrew Halaney (11): scsi: ufs: qcom: Perform read back after writing reset bit scsi: ufs: qcom: Perform read back after writing REG_UFS_SYS1CLK_1US scsi: ufs: qcom: Perform read back after writing testbus config scsi: ufs: qcom: Perform read back after writing unipro mode scsi: ufs: qcom: Perform read back after writing CGC enable scsi: ufs: cdns-pltfrm: Perform read back after writing HCLKDIV scsi: ufs: core: Perform read back after writing UTP_TASK_REQ_LIST_BASE_H scsi: ufs: core: Perform read back after disabling interrupts scsi: ufs: core: Perform read back after disabling UIC_COMMAND_COMPL scsi: ufs: core: Perform read back to commit doorbell scsi: ufs: core: Perform read back before writing run/stop regs drivers/ufs/core/ufshcd.c | 10 +++++----- drivers/ufs/host/cdns-pltfrm.c | 2 +- drivers/ufs/host/ufs-qcom.c | 14 ++++++-------- drivers/ufs/host/ufs-qcom.h | 12 ++++++------ 4 files changed, 18 insertions(+), 20 deletions(-) --- base-commit: 20d857259d7d10cd0d5e8b60608455986167cfad change-id: 20231208-ufs-reset-ensure-effect-before-delay-6e06899d5419 Best regards,