linux-kernel - Re: [linux-sunxi] [PATCH v2 6/8] ARM: dts: sun8i: a83t: Move mmc1 pinctrl setting to dtsi file

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Date:   Thu, 19 Oct 2017 16:24:32 +0800
From:   Chen-Yu Tsai <wens@...e.org>
To:     Icenowy Zheng <icenowy@...c.io>
Cc:     Chen-Yu Tsai <wens@...e.org>,
        Joonas Kylmälä <joonas.kylmala@....fi>,
        Lee Jones <lee.jones@...aro.org>,
        Maxime Ripard <maxime.ripard@...e-electrons.com>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        devicetree <devicetree@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        linux-sunxi <linux-sunxi@...glegroups.com>,
        Quentin Schulz <quentin.schulz@...e-electrons.com>
Subject: Re: [linux-sunxi] [PATCH v2 6/8] ARM: dts: sun8i: a83t: Move mmc1
 pinctrl setting to dtsi file

On Thu, Oct 19, 2017 at 4:18 PM,  <icenowy@...c.io> wrote:
> 在 2017-10-19 14:48，Chen-Yu Tsai 写道：
>>
>> On Wed, Oct 18, 2017 at 11:00 PM, Joonas Kylmälä <joonas.kylmala@....fi>
>> wrote:
>>>
>>> Hi,
>>>
>>> Chen-Yu Tsai:
>>>>
>>>> mmc1 only has 1 possible pinmux setting.
>>>
>>>
>>> What if someone is using the MMC with bus width 1 and then using the
>>> remaining 3 pins for something else?
>>
>>
>> I would very much like to see such a design. Currently the devices
>> we see all follow Allwinner's reference design, with only minor
>> modifications. As such, mmc1 is used exclusively for connecting
>> SDIO-based WiFi modules.
>>
>> If such a radical(?) design is done, the vendor can always add
>> a "mmc1-1bit-pins" setting and override the default.
>
>
> I think this kind of thing happened on A13 -- the MMC2 of A13 is
> 8-bit, but Lichee Pi One wires it to a SD card slot (4-bit); then
> the remaining 4 data lines are wired out as GPIO. (Lichee Pi's
> do not like obeying reference design ;-) )

For MMC2 we have mmc2_pins (4-bit) and mmc2_8bit_emmc_pins (8-bit
+ emmc reset pin).

ChenYu

>
> But I think a MMC/SDIO device under 1-bit mode is too slow that
> maybe no one will use such a setup.
>
>>
>> ChenYu
>
>
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