[U-Boot] [PATCH v2a] AT91: add SD/MMC support

[Schleifer, Alexander]

The clock messages are ..

mmc: bus_hz is 99072000, setting clock 150000 Hz, block size 512
mmc: requested clock 150000 is too low; changed to 193500

But I found out, that the AT91Bootstrap initialization impacts the U-Boot code. If I use the AT91Bootstrap (without mci initialization) from NAND flash, the mmc init command successfully reads the card. It fails if I use the AT91Bootstrap with mci initialization.

The new driver may help me out of this - so I would be happy to test your patch ;)

Best Regards,
Alex

-----Original Message-----
From: Reinhard Meyer [mailto:u-boot at emk-elektronik.de] 
Sent: Friday, August 13, 2010 8:32 PM
To: Schleifer, Alexander
Cc: u-boot at lists.denx.de
Subject: Re: [U-Boot] [PATCH v2a] AT91: add SD/MMC support

Dear Schleifer, Alexander,
> Thanks for your reply...
> 
> The CID part is:
> mmc: response: 1a50514d 53202020 1018301a ec007b8b
> Manufacturer ID:       1A
> OEM/Application ID:    5051
> Product name:          MS
> Product Revision:      1.0
> Product Serial Number: 405805804
> Manufacturing Date:    07/11
> 
> The CSD part is:
> mmc: response: 005e0032 5f5983cf edb6ff87 9640003f raw CSD data: 
> 005e0032 5f5983cf edb6ff87 9640003f Read block length: 512
>   (Supports partial reads)
> Card capacity: 244 Mbytes
> Warning: Using maximum data timeout
> mmc: Using 983040 cycles data timeout (DTOR=0x7f)

I miss the clock messages here. Whats the MCK and which divider is calculated?

> mmc: bread failed, status = 0040c0e5, card status = 00000900
0040c0e5=
DTOE=1(data time out error)
TXBUFE=1
RXBUFF=1(rx buffer full)
and other bits

That seems to me like some timing problem, or a hardware problem, where reading data with slow clock (used to get CID/CSD) works, but reading at several MHz (depending on card) does not work.
Besides the clock calculation in this driver rounds the divider down, so on a typical system a 25MHz card will receive a 48 MHz clock instead of a 24 MHz. I figured this out while testing the new driver...

If you really want to bother with this now old driver use this excerpt from the new driver:

	debug("mci: bus_hz is %u, setting clock %u Hz, block size %u\n",
		bus_hz, hz, blklen);
	if (hz > 0) {
		/* find lowest clkdiv yielding a rate <= than requested */
		for (clkdiv=0; clkdiv<255; clkdiv++) {
			if ((bus_hz / (clkdiv+1) / 2) <= hz)
				break;
		}
	}
	printf("mci: setting clock %u Hz, block size %u\n",
		(bus_hz / (clkdiv+1)) / 2, blklen);

If you have two days patience, wait for the new driver, I will be most happy to have a tester ;)

Best Regards,
Reinhard