Re: MMC error on Exynos4210 board

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+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?

-- 
Regards,
Sachin.
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