[PATCH v4 2/4] mmc: starfive: Add sdio/emmc driver support

[Shengyu Qu]

Hello William,

> On 2023/3/29 0:08, Shengyu Qu wrote:
>> Hello William,
>>
>> Sorry for making noise about this, but seems deleted voltage swtich function
>>
>> doesn't help about this. But there's still a problem about eMMC speed. Currently
>>
>> only about 20MB/s maximum reading speed could be reached when using eMMC
>>
>> on VF2, any idea about this?
>>
>> Best regards,
>>
>> Shengyu
>>
>> 在 2023/3/28 0:01, Shengyu Qu 写道:
>>> Hello William,
>>>
>>> I'm digging into downstream mmc driver these days and found a problem
>>>
>>> that current version mainline driver doesn't has a voltage switch function for
>>>
>>> it. Downstream older version has one but was deleted in this commit [1].
>>>
>>> It was deleted since vf2's SD slot doesn't have 1.8V input but commiter forgot
>>>
>>> that vf2's eMMC slot has a proper 1.8V input.
>>>
>>> So could you add voltage switch function for mainline? I've met a eMMC speed
>>>
>>> problem possibly due to it.
>>>
>>> Best regards,
>>>
>>> Shengyu
>>>
> 
> Hi Shengyu,
> 
> Sorry for the late reply.
> 
> First of all, I will consider adding voltage switch function, but the implementation
> method is to configure the pmic register configuration in dts, and the implementation
> interface will use the voltage switch function in dw_mmc.c.
> 
> As for speed, the main reason for the low rate is the clock of JH7110 and the
> associated IO driving strength, in this limit, the maximum reading speed I tested was
> about 50Mb/s.
> 
> I will try to reproduce your problem and try to solve it. Thanks for suggestions.
> 
> Best regards,
> William
I found out the reason and fixed that. dmwci driver needs vqmmc supply
configured in device tree and a successful voltage change to actually
enable 1.8v mode, even 1.8 supply actually already physically exists.
So to solve this problem, I wrote AXP15060 driver and device tree
bindings basing on -upstream branch and gets over 75MB/s read speed. The
driver series is already under review here:

https://lore.kernel.org/all/TY3P286MB26117891DFB2DD615A7C54EF98969@TY3P286MB2611.JPNP286.PROD.OUTLOOK.COM/

Best regards,
Shengyu
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