How use a dual MMC configuration on the AM335x-EVM

Ulf,

So you are only using MMC1 to load an SD card during runtime?

Device mounting is handled by 'udev' in linux. When a device is detected, the appropriate device node is created by udev.

If an MMC card is found on boot, udev will automatically create a node for that device to be used by the kernel.

For more information, please see this previous e2e post: http://e2e.ti.com/support/dsp/sitara_arm174_microprocessors/f/791/t/196388.aspx 

Yes, once the card is detected, udev can do wonders, but I want to know :

* what configures the pins to use the MMC1 functionality?

* what registers MMC1 with the MMC/SD/SDIO subsystem?

MMC0 is initialized in board-am335x-evm.c but not MMC1.

The link you provided makes me think that he comment is bogus, and that board-am335x-evm.c

eeds to be modified for MMC1 to work at all.

Ulf,

Ah, I assumed you already modified the board-am335x-evm.c file. I'll do my best to answer your questions:

* The pins are configured via the board-am335x-evm.c file or...(http://processors.wiki.ti.com/index.php/AM335x_PSP_User%27s_Guide#Modifying_Pin_Mux_settings)

* To the best of my knowledge, the card is initialized by having the am335x detect the assertion of the card detect pin while the SD clock is running.

From the linked post:

"Linux uses aggressive Power management method to save Power. When MMC is not in use, clock is switched off to MMC module. Because of this, if CD & WP from MMC Controller is used, Card insertion/removal or Write-protect detection will not work properly.[...]"

Let me know if that clarifies some things. Hopefully someone else can jump in and give their more experienced opinion.

Best,

Keegan

The problem was that I had to enable the correct "profile".

Otherwise, the secondary MMC is not available.

Unfortunately, my SDIO card seems to have lots of problem in the secondary MMC connector.

These problems does not exist if I put it in the primary MMC connector (on the baseboard).

Initially I booted from the SD-Card, and then ran NFS, but now I boot from NAND flash
and use MMC0, which seems to work, albeit slow.

The AM335x seems to have restrictions on scatter/gather for the MMC, making the throughput about
half of an Atmel ARM9 we are using at the moment.

I will bring that up in another post.

Have you made any progress?

We have the same issue of slow throughput out of the SDIO interface (MMC0).

Thanks. 

The problem is that the SDIO driver does not enable the CIRQ interrupt

and does not export an interrupt handler.

This means that the SDIO stack polls the card.

Have asked why, in another thread, but no answer.

Hi,Ulf Samuelsson

      In my kernel, only the mmc0 module can work well when kernel boot,  I want to enable the mmc1 modules when kernel boot, how should I do to implement it？

best regards!