Re: [PATCH 04/15] MIPS: dts: img: pistachio_marduk: Switch mmc to 1 bit mode

From: Andreas FÃrber
Date: Tue Jul 24 2018 - 18:15:50 EST

Am 22.07.2018 um 23:19 schrieb Andreas FÃrber:
> From: Ian Pozella <Ian.Pozella@xxxxxxxxxx>
> The mmc block in Pistachio allows 1 to 8 data bits to be used.
> Marduk uses 4 bits allowing the upper 4 bits to be allocated
> to the Mikrobus ports. However these bits are still connected
> internally meaning the mmc block recieves signals on all data lines


I had fixed a number of typos from the downstream patches already, but
this one slipped through.


> and seems the internal HW CRC checks get corrupted by this erroneous
> data.
> We cannot control what data is sent on these lines because they go
> to external ports. 1 bit mode does not exhibit the issue hence the
> safe default is to use this. If a user knows that in their use case
> they will not use the upper bits then they can set to 4 bit mode in
> order to improve performance.
> Also make sure that the upper 4 bits don't get allocated to the mmc
> driver (the default is to assign all 8 pins) so they can be allocated
> to other drivers. Allocating all 4 despite setting 1 bit mode as this
> matches what is there in hardware.
> Signed-off-by: Ian Pozella <Ian.Pozella@xxxxxxxxxx>
> Signed-off-by: Andreas FÃrber <afaerber@xxxxxxx>

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