linux-kernel - Re: [PATCH V2 0/5] mmc: mmci: add busy detect for stm32 sdmmc variant

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Message-ID: <CAPDyKFo4Y9PF_QL47rO2c_szUHahPMuzHV=j_SL9dxvAzst17w@mail.gmail.com>
Date:   Tue, 21 May 2019 09:56:09 +0200
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Ludovic BARRE <ludovic.barre@...com>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Alexandre Torgue <alexandre.torgue@...com>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        DTML <devicetree@...r.kernel.org>,
        "linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
        linux-stm32@...md-mailman.stormreply.com
Subject: Re: [PATCH V2 0/5] mmc: mmci: add busy detect for stm32 sdmmc variant

On Tue, 21 May 2019 at 09:38, Ludovic BARRE <ludovic.barre@...com> wrote:
>
> hi Ulf
>
> Just a "gentleman ping" about the rest of series.
> "mmc: mmci: add busy detect for stm32 sdmmc variant"

Thanks!

It's been a busy period and I am currently traveling. My plan is to
look at in detail beginning of next week when get back home. I hope
that's okay.

Kind regards
Uffe

>
> Regards
> Ludo
>
> On 5/3/19 3:29 PM, Ulf Hansson wrote:
> > On Tue, 30 Apr 2019 at 14:06, Ludovic BARRE <ludovic.barre@...com> wrote:
> >>
> >>
> >>
> >> On 4/30/19 1:13 PM, Ulf Hansson wrote:
> >>> On Fri, 26 Apr 2019 at 09:46, Ludovic Barre <ludovic.Barre@...com> wrote:
> >>>>
> >>>> From: Ludovic Barre <ludovic.barre@...com>
> >>>>
> >>>> This patch series adds busy detect for stm32 sdmmc variant.
> >>>> Some adaptations are required:
> >>>> -Avoid to check and poll busy status when is not expected.
> >>>> -Clear busy status bit if busy_detect_flag and busy_detect_mask are
> >>>>    different.
> >>>> -Add hardware busy timeout with MMCIDATATIMER register.
> >>>>
> >>>> V2:
> >>>> -mmci_cmd_irq cleanup in separate patch.
> >>>> -simplify the busy_detect_flag exclude
> >>>> -replace sdmmc specific comment in
> >>>> "mmc: mmci: avoid fake busy polling in mmci_irq"
> >>>> to focus on common behavior
> >>>>
> >>>> Ludovic Barre (5):
> >>>>     mmc: mmci: cleanup mmci_cmd_irq for busy detect feature
> >>>>     mmc: mmci: avoid fake busy polling in mmci_irq
> >>>>     mmc: mmci: fix clear of busy detect status
> >>>>     mmc: mmci: add hardware busy timeout feature
> >>>>     mmc: mmci: add busy detect for stm32 sdmmc variant
> >>>>
> >>>>    drivers/mmc/host/mmci.c | 61 ++++++++++++++++++++++++++++++++++++++-----------
> >>>>    drivers/mmc/host/mmci.h |  3 +++
> >>>>    2 files changed, 51 insertions(+), 13 deletions(-)
> >>>>
> >>>> --
> >>>> 2.7.4
> >>>>
> >>>
> >>> Ludovic, just wanted to let you know that I am reviewing and testing
> >>> this series.
> >>>
> >>> However, while running some tests on Ux500 for validating the busy
> >>> detection code, even without your series applied, I encounter some odd
> >>> behaviors. I am looking into the problem to understand better and will
> >>> let you know as soon as I have some more data to share.
> >>
> >> Oops, don't hesitate to share your status, if I could help.
> >
> > Thanks! Good and bad news here, then.
> >
> > I now understand what is going on - and there is certainly room for
> > improvements here, but more importantly the actual mmci busy detection
> > works as expected.
> >
> > When it comes to improvements, the main issue I have found is how we
> > treat DATA WRITES. In many cases we simply don't use the HW busy
> > detection at all, but instead rely on the mmc core to send CMD13 in a
> > loop to poll. Well, then if the polling would have consisted of a
> > couple of CMD13s that wouldn't be an issue, but my observations is
> > rather that the numbers of CMD13 sent to poll is in the range or
> > hundreds/thousands - per each WRITE request!
> >
> > I am going to send a patch (or two) that improves the behavior. It
> > might even involve changing parts in core layer, not sure how the end
> > result will look like yet.
> >
> > In any case, I have applied patch 1 and patch2 for next, as the tests
> > turned out well at my side. I also took the liberty of updating some
> > of the comments/changelogs, please have look and tell if there is
> > something you want to change.
> >
> > I will continue with the rest of series next week.
> >
> > Kind regards
> > Uffe
> >