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 16:18:04 +0800
From:   icenowy@...c.io
To:     wens@...e.org
Cc:     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

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 ;-) )

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

> 
> ChenYu