linux-kernel - Re: [PATCH 4.19.113 0/3] Fix for long operation cmds busy detection

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Date:   Mon, 20 Apr 2020 09:01:35 +0200
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Greg KH <gregkh@...uxfoundation.org>
Cc:     Sowjanya Komatineni <skomatineni@...dia.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        "(Exiting) Baolin Wang" <baolin.wang@...aro.org>,
        Kate Stewart <kstewart@...uxfoundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Bradley Bolen <bradleybolen@...il.com>,
        Faiz Abbas <faiz_abbas@...com>,
        Thierry Reding <thierry.reding@...il.com>,
        Jon Hunter <jonathanh@...dia.com>,
        Bitan Biswas <bbiswas@...dia.com>,
        Aniruddha Tvs Rao <anrao@...dia.com>,
        linux-tegra <linux-tegra@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>
Subject: Re: [PATCH 4.19.113 0/3] Fix for long operation cmds busy detection

On Sun, 19 Apr 2020 at 18:52, Greg KH <gregkh@...uxfoundation.org> wrote:
>
> On Sun, Apr 19, 2020 at 09:23:39AM -0700, Sowjanya Komatineni wrote:
> >
> > On 4/19/20 12:20 AM, Greg KH wrote:
> > > External email: Use caution opening links or attachments
> > >
> > >
> > > On Fri, Apr 17, 2020 at 12:14:01PM -0700, Sowjanya Komatineni wrote:
> > > > This series includes manually backported changes that implements Tegra
> > > > specific timeout callback to switch between finite and infinite HW busy
> > > > detection wait modes.
> > > >
> > > > sdhci-tegra driver patch implements set_timeout callback based on one of
> > > > the sdhci host driver patch that refactors sdhci_set_timeout and allows
> > > > drivers to call __sdhci_set_timeout with their timeout callback
> > > > implementation.
> > > >
> > > > Both of these patches are manually backported in this series.
> > > Is this a bugfix or a new feature?  I can't tell, but it feels like it's
> > > a new feature.  What's wrong with just using the 5.4.y kernel tree?
> > >
> > > thanks,
> > >
> > > greg k-h
> > Ulf recent patches for increased timeout adds capability
> > MMC_CAP_NEED_RSP_BUSY for sdhci-tegra as well.
> >
> > So, it will always use R1B for R1B type commands so there are no known bugs
> > or failures with mmc devices we use on our platforms.
>
> I have no idea what this means, sorry.
>
> > So, we can treat this patch as an improvement for long operation commands
> > where HW will wait as long as device is busy.
>
> Ok, so this isn't a regression and can't match the stable kernel rules,
> sorry.

Let me help to clarify. This isn't a regression, correct. However, the
patch fixes a long outstanding bug for sdhci-tegra.

For some SD/MMC commands, the mmc core may provide a long busy timeout
trusting the mmc host to cope with it. It has turned out that
sdhci-tegra didn't, thus it may report a cmd-timeout error, while in
fact it shouldn't.

I believe that is what the small series of patches should be addressing.

Kind regards
Uffe