在 2017-10-19 14:48，Chen-Yu Tsai 写道：

On Wed, Oct 18, 2017 at 11:00 PM, Joonas Kylmälä 
[off-list ref] wrote:

quoted

Hi,

Chen-Yu Tsai:

quoted

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

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