[U-Boot] MMC interfaces on AM335x

[U-Boot] MMC interfaces on AM335x

[Andy Pont]

Hello,

I am working on a port of U-Boot to a custom hardware platform based on the
TI AM3354.  According to the schematics from the hardware design company,
the AM3354 has a 4bit MMC interface (MMC0) which has been connected to a uSD
card connector.
There is a second interface (8bit) connected to GPMC signals which is
connected to a Micron eMMC device labelled as MMC1.

U-Boot and the Linux kernel will be stored in a separate SPI flash device
and the eMMC card will hold the root file system and the uSD card for
removable storage.  Am I correct in thinking that if U-Boot boots with no
uSD card installed the eMMC device will be accessed as device 0 e.g.

U-Boot> fatload mmc 0 ...

but if it boots with a uSD card fitted then the eMMC device will be device
1, e.g.

U-Boot> fatload mmc 1 ...

Is there any way to force U-Boot always to map the eMMC device as device 0?

Thanks,

Andy.

[U-Boot] MMC interfaces on AM335x

[Tom Rini]

On Tue, Aug 26, 2014 at 01:57:23PM +0100, Andy Pont wrote:
> Hello,
> 
> I am working on a port of U-Boot to a custom hardware platform based on the
> TI AM3354.  According to the schematics from the hardware design company,
> the AM3354 has a 4bit MMC interface (MMC0) which has been connected to a uSD
> card connector.
> There is a second interface (8bit) connected to GPMC signals which is
> connected to a Micron eMMC device labelled as MMC1.
> 
> U-Boot and the Linux kernel will be stored in a separate SPI flash device
> and the eMMC card will hold the root file system and the uSD card for
> removable storage.  Am I correct in thinking that if U-Boot boots with no
> uSD card installed the eMMC device will be accessed as device 0 e.g.

No.  If you build with support for both MMC interfaces (and configure
them in U-Boot) then the first one is 0 and the second is 1, even if
there is no card inserted.

> U-Boot> fatload mmc 0 ...
> 
> but if it boots with a uSD card fitted then the eMMC device will be device
> 1, e.g.
> 
> U-Boot> fatload mmc 1 ...
> 
> Is there any way to force U-Boot always to map the eMMC device as device 0?

Only by removing support for the SD slot.  You're better off in this
case knowing that eMMC will always be 1.

-- 
Tom
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