linux-kernel - Re: [PATCH v2 0/3] iommu: Enable non-strict DMA on QCom SD/MMC

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Date:   Thu, 8 Jul 2021 10:08:56 +0200
From:   Joerg Roedel <joro@...tes.org>
To:     Doug Anderson <dianders@...omium.org>
Cc:     Will Deacon <will@...nel.org>, Robin Murphy <robin.murphy@....com>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        John Garry <john.garry@...wei.com>,
        Rob Clark <robdclark@...omium.org>, quic_c_gdjako@...cinc.com,
        Saravana Kannan <saravanak@...gle.com>,
        Rajat Jain <rajatja@...gle.com>,
        Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>,
        Veerabhadrarao Badiganti <vbadigan@...eaurora.org>,
        Linux MMC List <linux-mmc@...r.kernel.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        linux-pci@...r.kernel.org,
        "list@....net:IOMMU DRIVERS <iommu@...ts.linux-foundation.org>, Joerg
        Roedel <joro@...tes.org>," <iommu@...ts.linux-foundation.org>,
        Sonny Rao <sonnyrao@...omium.org>,
        Joel Fernandes <joel@...lfernandes.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Jonathan Corbet <corbet@....net>,
        Jordan Crouse <jordan@...micpenguin.net>,
        Konrad Dybcio <konrad.dybcio@...ainline.org>,
        Krishna Reddy <vdumpa@...dia.com>,
        "Maciej W. Rozycki" <macro@...am.me.uk>,
        Nicolin Chen <nicoleotsuka@...il.com>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Randy Dunlap <rdunlap@...radead.org>,
        Thierry Reding <thierry.reding@...il.com>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Linux Doc Mailing List <linux-doc@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 0/3] iommu: Enable non-strict DMA on QCom SD/MMC

On Wed, Jul 07, 2021 at 01:00:13PM -0700, Doug Anderson wrote:
> a) Nothing is inherently broken with my current approach.
> 
> b) My current approach doesn't make anybody terribly upset even if
> nobody is totally in love with it.

Well, no, sorry :)

I don't think it is a good idea to allow drivers to opt-out of the
strict-setting. This is a platform or user decision, and the driver
should accept whatever it gets.

So the real question is still why strict is the default setting and how
to change that. Or document for the users that want performance how to
change the setting, so that they can decide.

Regards,

	Joerg