linux-kernel - Re: [PATCH v4 2/4] mmc: starfive: Add sdio/emmc driver support

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Date:   Tue, 11 Apr 2023 10:54:42 +0800
From:   William Qiu <william.qiu@...rfivetech.com>
To:     Shengyu Qu <wiagn233@...look.com>,
        <linux-riscv@...ts.infradead.org>, <devicetree@...r.kernel.org>,
        <linux-mmc@...r.kernel.org>
CC:     Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Jaehoon Chung <jh80.chung@...sung.com>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 2/4] mmc: starfive: Add sdio/emmc driver support



On 2023/4/11 2:04, Shengyu Qu wrote:
> 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

Hi Shengyu,

Thanks for the patch series. I will try it on my branch.

Best regards,
William