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

[Ludovic BARRE]

hi Ulf

On 5/3/19 3:29 PM, Ulf Hansson wrote:
> On Tue, 30 Apr 2019 at 14:06, Ludovic BARRE <ludovic.barre@xxxxxx> wrote:
> > On 4/30/19 1:13 PM, Ulf Hansson wrote:
> > > On Fri, 26 Apr 2019 at 09:46, Ludovic Barre <ludovic.Barre@xxxxxx> wrote:
> > > > From: Ludovic Barre <ludovic.barre@xxxxxx>
> > > >
> > > > 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.

yes, these will improve the drivers without hardware busy completion.
great

> 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.

thanks, and good week-end.

> Kind regards
> Uffe