SD controller now initialized; still need to read SD ID and perform data block transfer. Some questions on TFS and booting an application image

[Jarielle Catbagan]

Hi Ed and all:

Initializing the SD controller on the AM335x took a bit longer than I
expected which was mostly a result of encountering some issues with
the SD controller initialization, specifically the clocks that are
involved.

Now that I was able to resolve the issues I was facing, I was able to
initiate CMD0 (GO_IDLE_STATE), CMD8 (SEND_IF_COND), and CMD55
(APP_CMD) and was able to receive appropriate responses from any
arbitrary SD card that is connected.

Right now I have the interface setup using 4-bit SD mode with the SD
clock frequency set to 6MHz and currently operating on 3.0 V.

Currently, I am looking into reading the ID register and to write and
read to/from the SD card.  I suspect that this would be much easier
now since the SD controller is set up properly already.

As I am approaching in getting ready to integrate the SD code, i.e.
establishing the necessary code to get the "sd" command working, I am
also simultaneously looking into TFS.

It looks like a RAM-based TFS would have to be set up as both the
MMC/SD can not be accessed linearly.

Once TFS is set up, I would say that the next step would be to have
the ability to transfer an application image from the SD card into TFS
for uMon to boot from or, if it's possible, to transfer a raw
application image from SD into DDR3 and then pass control to the entry
point of the application image.

Am I approaching the idea of TFS and booting an application image correctly.

Thanks.