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

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Message-ID: <7e15c8ec-f851-b0d3-a3ce-dfad2a398e78@st.com>
Date:   Tue, 21 May 2019 11:17:48 +0200
From:   Ludovic BARRE <ludovic.barre@...com>
To:     Ulf Hansson <ulf.hansson@...aro.org>
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 5/21/19 9:56 AM, Ulf Hansson wrote:
> 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.

yes, I understand, it's just to not forget me :-)

> 
> 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
>>>