Re: MMC error on Exynos4210 board

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On Thu, Jun 19, 2014 at 2:40 PM, Tim Kryger <tim.kryger@xxxxxxxxx> wrote:
> On Thu, Jun 19, 2014 at 1:49 AM, Sachin Kamat <spk.linux@xxxxxxxxx> wrote:
>> +cc Some relevant guys from Samsung
>>
>> On Thu, Jun 19, 2014 at 2:12 PM, Tim Kryger <tim.kryger@xxxxxxxxx> wrote:
>>> On Wed, Jun 18, 2014 at 8:54 PM, Sachin Kamat <spk.linux@xxxxxxxxx> wrote:
>>>
>>>>> On Wed, Jun 18, 2014 at 4:33 AM, Sachin Kamat <spk.linux@xxxxxxxxx> wrote:
>>>
>>>>>> I see the below error on Exynos4210 based Origen board with linux-next
>>>>>> (20140618).
>>>>>> Reverting the below commit works fine.
>>>>>>
>>>>>> Commit: 8d02e775a6 "mmc: sdhci: Use mmc core regulator infrastucture"
>>>
>>>>>>
>>>>>> -- [    2.068992] sdhci: Secure Digital Host Controller Interface driver
>>>>>> [    2.075059] sdhci: Copyright(c) Pierre Ossman
>>>>>> [    2.079762] of_get_named_gpiod_flags: can't parse gpios property of
>>>>>> node '/sdhci@12510000[0]'
>>>>>> [    2.088021] s3c-sdhci 12510000.sdhci: clock source 2: mmc_busclk.2
>>>>>> (50000000 Hz)
>>>>>> [    2.095322] of_get_named_gpiod_flags: can't parse gpios property of
>>>>>> node '/sdhci@12510000[0]'
>>>>>> [    2.103794] of_get_named_gpiod_flags: can't parse gpios property of
>>>>>> node '/sdhci@12510000[0]'
>>>>>> [    2.112478] s3c-sdhci 12510000.sdhci: No vqmmc regulator found
>>>>>> [    2.118117] mmc0: Hardware doesn't report any support voltages.
>>>>>> [    2.124004] s3c-sdhci 12510000.sdhci: sdhci_add_host() failed
>>>>>> [    2.130080] of_get_named_gpiod_flags: can't parse gpios property of
>>>>>> node '/sdhci@12530000[0]'
>>>>>> [    2.138352] s3c-sdhci 12530000.sdhci: clock source 2: mmc_busclk.2
>>>>>> (16666667 Hz)
>>>>>> [    2.145661] of_get_named_gpiod_flags: can't parse gpios property of
>>>>>> node '/sdhci@12530000[0]'
>>>>>> [    2.154139] of_get_named_gpiod_flags: can't parse gpios property of
>>>>>> node '/sdhci@12530000[0]'
>>>>>> [    2.162834] s3c-sdhci 12530000.sdhci: No vqmmc regulator found
>>>>>> [    2.168464] mmc0: Hardware doesn't report any support voltages.
>>>>>> [    2.174349] s3c-sdhci 12530000.sdhci: sdhci_add_host() failed
>>>
>>>>>> [    2.336148] Waiting for root device /dev/mmcblk0p1...
>>>
>>>> FYI, the board has a 2.8V fixed regulator supply connected to the MMC.
>>>> You may refer to arch/arm/boot/dts/exynos4210-origen.dts for more details.
>>>
>>> A 2.8v regulator results in mmc->ocr_avail being set to MMC_VDD_27_28
>>> | MMC_VDD_28_29.
>>>
>>> The SDHCI capabilities register only indicates support of three voltage levels
>>>   - 1.8v: SDHCI_CAN_VDD_180 => MMC_VDD_165_195
>>>   - 3.0v: SDHCI_CAN_VDD_300 => MMC_VDD_29_30 | MMC_VDD_30_31
>>>   - 3.3v: SDHCI_CAN_VDD_330 => MMC_VDD_32_33 | MMC_VDD_33_34
>>>
>>> Even if all capability bits of the host controller were set, there
>>> still wouldn't be any overlap.  Thus you see a "Hardware doesn't
>>> report any support voltages" message.
>>>
>>> Previously, this issue was being swept under the rug by cec2e21 mmc:
>>> sdhci: Use regulator min/max voltage range according to spec.  That
>>> change hacked up the voltage range checks such that with your 2.8v
>>> fixed regulator, the driver would believe the host could support
>>> MMC_VDD_29_30 | MMC_VDD_30_31 | MMC_VDD_32_33 | MMC_VDD_33_34.  The
>>> driver would start down the path of commanding 3.3v-3.4v (the highest
>>> voltage range believed to be supported).  At the last second, the
>>> driver would see the regulator was fixed and blindly skip over the set
>>> voltage operation, saving it from failure.
>>>
>>> Since my patch eliminates the bogus voltage range checks, your board
>>> is now getting caught playing too loose with the SDHCI regulator
>>> voltages.
>>>
>>> Furthermore, the fixed regulator special-case logic that helped hide
>>> your issue should also be considered for removal given that fixed
>>> regulators now behave properly thanks to c00dc35 regulator: core:
>>> Allow regulator_set_voltage for fixed regulators.
>>
>> Thanks for the detailed explanation. What do you propose to get this fixed?
>
> I'm not really sure of the best path forward.  I suppose you could
> modify your device tree to lie about the voltage of the fixed
> regulator.  Changing it to 3.0v should allow it to boot up but that is
> definitely a hack.

Or I could simply remove the vmmc-supply property altogether (as it is optional)
and get the board to work.

> It would be nice if the driver could be extended
> to handle the peculiarities of your board in a deliberate manner but
> limiting the common sdhci driver to supporting only the three voltages
> from the spec also seems sensible.

Until such time that the driver gets fixed to handle 2.8V fixed supply your
current patch leaves several of Exynos boards broken for now.

-- 
Regards,
Sachin.
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