This also fixes a few minor violations of the SD protocol, such as running
the bus at high speed during the card identification sequence.
The sdcard_init() routine now probes for SDHC cards so that later read
requests can make needed adjustments between block and byte offsets based
on card type.
There is a new MCI_readblocks() function that takes block number and block
count parameters instead of byte-offset values. Using this routine, boot
loader code can load a kernel from any location on an SDHC or standard SD.
The old MCI_read() interface remains unchanged so that existing customized
boot loader code will still keep working without changes. Using this
routine, boot loaders can load a kernel from anywhere in the first 4GB of
an SDHC card (or of course any location on a standard SD card).
A new sdcard_use4wire() routine allows boot loaders to request 4-bit
transfers; it should be called after sdcard_init(). The sdcard_init()
routine no longer assumes the hardware is 4-wire capable and by default
sets things up for 1-bit transfers. (4-wire mode is unreliable on
at91rm9200, works on later SoCs.)
PR: 155894
Submitted by: me. years ago.
8926f21ce1