linux-kernel - Re: [PATCH v2] mmc: sdhci-of-esdhc: fixup PRESENT

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Message-ID: <2119c4c1fa8a6943a2f8da05f3be2db2@walle.cc>
Date:   Mon, 14 Nov 2016 10:52:31 +0100
From:   Michael Walle <michael@...le.cc>
To:     Adrian Hunter <adrian.hunter@...el.com>
Cc:     "Y.B. Lu" <yangbo.lu@....com>, linux-kernel@...r.kernel.org,
        linux-mmc@...r.kernel.org, Ulf Hansson <ulf.hansson@...aro.org>,
        yangbo lu <yangbo.lu@...escale.com>
Subject: Re: [PATCH v2] mmc: sdhci-of-esdhc: fixup PRESENT_STATE read

Am 2016-11-14 10:37, schrieb Adrian Hunter:
> On 14/11/16 10:50, Michael Walle wrote:
>> Am 2016-11-14 04:00, schrieb Y.B. Lu:
>>>> -----Original Message-----
>>>> From: Michael Walle [mailto:michael@...le.cc]
>>>> Sent: Saturday, November 12, 2016 12:04 AM
>>>> To: linux-kernel@...r.kernel.org
>>>> Cc: linux-mmc@...r.kernel.org; Ulf Hansson; Adrian Hunter; yangbo 
>>>> lu;
>>>> Michael Walle
>>>> Subject: [PATCH v2] mmc: sdhci-of-esdhc: fixup PRESENT_STATE read
>>>> 
>>>> Since commit 87a18a6a5652 ("mmc: mmc: Use ->card_busy() to detect 
>>>> busy
>>>> cards in __mmc_switch()") the ESDHC driver is broken:
>>>>   mmc0: Card stuck in programming state! __mmc_switch
>>>>   mmc0: error -110 whilst initialising MMC card
>>>> 
>>>> Since this commit __mmc_switch() uses ->card_busy(), which is
>>>> sdhci_card_busy() for the esdhc driver. sdhci_card_busy() uses the
>>>> PRESENT_STATE register, specifically the DAT0 signal level bit. But 
>>>> the
>>>> ESDHC uses a non-conformant PRESENT_STATE register, thus a read 
>>>> fixup is
>>>> required to make the driver work again.
>>>> 
>>>> Signed-off-by: Michael Walle <michael@...le.cc>
>>>> Fixes: 87a18a6a5652 ("mmc: mmc: Use ->card_busy() to detect busy 
>>>> cards in
>>>> __mmc_switch()")
>>>> ---
>>>> v2:
>>>>  - use lower bits of the original value (that was actually a typo)
>>>>  - add fixes tag
>>>>  - fix typo
>>>> 
>>>>  drivers/mmc/host/sdhci-of-esdhc.c | 12 ++++++++++++
>>>>  1 file changed, 12 insertions(+)
>>>> 
>>>> diff --git a/drivers/mmc/host/sdhci-of-esdhc.c 
>>>> b/drivers/mmc/host/sdhci-
>>>> of-esdhc.c
>>>> index fb71c86..f9c84bb 100644
>>>> --- a/drivers/mmc/host/sdhci-of-esdhc.c
>>>> +++ b/drivers/mmc/host/sdhci-of-esdhc.c
>>>> @@ -66,6 +66,18 @@ static u32 esdhc_readl_fixup(struct sdhci_host 
>>>> *host,
>>>>              return ret;
>>>>          }
>>>>      }
>>>> +    /*
>>>> +     * The DAT[3:0] line signal levels and the CMD line signal 
>>>> level is
>>>> +     * not compatible with standard SDHC register. Move the
>>>> corresponding
>>>> +     * bits around.
>>>> +     */
>>>> +    if (spec_reg == SDHCI_PRESENT_STATE) {
>>>> +        ret = value & ~0xf8000000;
>>> 
>>> [Lu Yangbo-B47093] I think the bits which should be cleaned before
>>> following '|=' are 0x01f00000 not 0xf8000000, right?
>>> :)
>> 
>> Its neither 0x01f00000 nor 0xf8000000 :( I'll put the bits definition 
>> into
>> the comment the next time, so everyone can review them. bit[31:24] are 
>> the
>> line DAT[7:0] line signal level. bit[23] is command signal level. All 
>> other
>> bits are the same as in the standard SDHC PRESENT_STATE register.
>> 
>> I want to keep all but the upper 9 bits from the original value, 
>> therefore,
>> this should be the correct mask:
>>     ret = value & ~0xff800000;
> 
> Why keep bits 22:20 ?  Isn't it more logical to keep 19:0 (i.e. ret = 
> value
> & 0xfffff)

These are 0 according to the datasheet but of course, it makes more 
sense to mask these, too.

-michael