From mboxrd@z Thu Jan  1 00:00:00 1970
From: Hannes Petermaier <hannes@petermaier.org>
Date: Tue, 05 Aug 2014 10:55:22 +0200
Subject: [U-Boot] mmc: question about capacity detection
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On 2014-08-05 09:20, Hannes Petermaier wrote:
> hi folks,
>
> i am actually trying to enable the "enhanced data area" on an 4GB emmc 
> device, this i've done successfully with the linux mmc-utils and the 
> card has after this "partitioning" 2GB user-partition.
>
> Linux kernel deals correctly with the card.
>
> U-Boot doesn't:
>
> "
> MMC: block number 0x301 exceeds max(0x0)
> spl: mmc blk read err - 0
> ### ERROR ### Please RESET the board ###
> "
>
> So i debugged around and found the capacity-calculation, which i don't 
> fully understand.
> "
>     if (mmc->high_capacity) {
>         csize = (mmc->csd[1] & 0x3f) << 16
>             | (mmc->csd[2] & 0xffff0000) >> 16;
>         cmult = 8;
>     } else {
>         csize = (mmc->csd[1] & 0x3ff) << 2
>             | (mmc->csd[2] & 0xc0000000) >> 30;
>         cmult = (mmc->csd[2] & 0x00038000) >> 15;
>     }
> "
> The else path does for my opinion the right calculation according the 
> mmc-specification, the "high_capacity" path i do not understand at 
> all, neither i found some specification for this.
>
> In fact my 4GB card (with 2GB enhanced area) works only with "the 
> else" path.
> my csd Registers:
>
> MMC-card dection:
> ocr    : 0xc0ff8080
> csd[0] : 0xd04f0132
> csd[1] : 0x0f5a13ff
> csd[2] : 0xffffffe7
> csd[3] : 0x8a4000f1
> c_size : 0x00000000003fffff
> c_mult : 0x0000000000000008
>
> U-Boot (BuR V2.0)# mmc info
> Device: OMAP SD/MMC
> Manufacturer ID: fe
> OEM: 14e
> Name: MMC04
> Tran Speed: 52000000
> Rd Block Len: 512
> MMC version 4.41
> High Capacity: Yes
> Capacity: 4 TiB
> Bus Width: 1-bit
>
> any ideas ?
>
> best regards,
> Hannes
>
I've digged a bit deeper and found an (for me, as newbie in this) 
interesting webpage:

http://www.hjreggel.net/cardspeed/special-sd.html

there i've found the key to understand the "high_capacity" path:
"...In CSD Version 2.0, the C_SIZE field was extended to 22 bit. The 
C_SIZE_MULT was dropped, assuming a preset multiplier of 2^10 . The 
READ_BL_LEN was kept, but the only value allowed is 9, indicating a 
block length of 512 bytes."

So the code should be as following:

-       if (mmc->high_capacity) {
+       if (mmc->high_capacity && mmc->read_bl_len == MMC_MAX_BLOCK_LEN) {

i'am correct in my thinking ? please some comment.
if yes - i will format a patch for this

best regards,
Hannes