[PATCH v2] ARM: shmobile: silk: add SDHI1 DT support

[Sergei Shtylyov]

Hello.

On 09/18/2015 05:56 AM, Magnus Damm wrote:

>>>>>>>> Define the SILK board dependent part of the SDHI1 (connected to micro-SD slot)
>>>>>>>> device nodes along with the necessary voltage regulators.
>>>>>>>>
>>>>>>>> Based on the original patch by Vladimir Barinov
>>>>>>>> <vladimir.barinov at cogentembedded.com>.
>>>>>>>>
>>>>>>>> Signed-off-by: Sergei Shtylyov <sergei.shtylyov at cogentembedded.com>
>>>>>>>>
>>>>>>>> ---
>>>>>>>> This patch is against 'renesas-devel-20150810-v4.2-rc6' tag of Simon Horman's
>>>>>>>> 'renesas.git' repo plus the R8A7794/SILK QSPI patches just re-posted. It needs
>>>>>>>> the R8A7794 GPIO patches in order to compile.
>>>>>>>>
>>>>>>>> Changes in version 2:
>>>>>>>> - removed not working SDHI0 stuff, renamed the patch;
>>>>>>>> - replaced SDHI1's "wp-gpios" property with "disable-wp".
>>>>>>>
>>>>>>> I am wondering if you could explain the motivation for the "disable-wp"
>>>>>>> update
>>>>>>
>>>>>>     Please see the comment in mmc_sd_get_ro().
>>>>>>
>>>>>>> and weather it is appropriate for other r8a779* dts files.
>>>>>>
>>>>>>     In case of micro-SD slots, yes.
>>>>>
>>>>>     The MMC binding document says it should only be specified if the
>>>>> controller has WP detection logic. We, so far, seem to have been replying on
>>>>> the GPIOs despite this logic is present (according to the R-Car gen2 SDHI
>>>>> manuals I have). The driver will first call mmc_gpio_get_ro() and when that
>>>>> fails due to "wp-gpios" not being specified, it proceeds to reading the
>>>>> register but that is forbidden by TMIO_MMC_WRPROTECT_DISABLE flag set for
>>>>> the R-Car gen1/2 chips, so 0 is always returned from tmio_mmc_get_ro().
>>>>> There seems to be no point in going that far (and doing the runtime PM
>>>>> dances) --
>>>
>>>     Alternatively, the driver could be fixed to check the flag before the RPM
>>> call unlike what it does now.
>>
>> If the driver can be updated to do the right thing then that seems
>> preferable to me. If so would it be the case that the presence of the
>> "disable-wp" property would not have any run-time effect?
>>>
>>>>> and MMC_CAP2_NO_WRITE_PROTECT (set when "disable-wp" is specified) prohibits
>>>>> doing that...
>>>>
>>>> That sounds reasonable to me.
>>>
>>>     I'm still wondering why TMIO_MMC_WRPROTECT_DISABLE is set for the R-Car
>>> SoCs. Morimoto-san, any comments? Your change logs are too terse. :-)
>>
>> I will follow up on this.

[...]
> Now what is the issue that you guys are having?

    My main issue is that I don't understand why checking the write protect 
bit is always prohibited for the R-Car SoCs (by setting 
TMIO_MMC_WRPROTECT_DISABLE), i.e. it can only be read via GPIO (though that 
GPIO is just an alias of the WP signal).

>>>> Some more questions from my side:
>>>
>>>> * What is the status of this patch
>>>
>>>     Tested, working.
>>>
>>>> * Can you prepare patches for r8a779* dts files for micro-SD slots?
>>>
>>>     Ugh, I probably can but won't promise anything.
>>
>> Likewise, ugh.

> What needs to be updated for R-Car Gen1 again?

    We haven't reached the agreement about the need for update yet.

> Thanks,
> / magnus

MBR, Sergei