Q: mmc au size

Hello all,

I have a question concerning the "au" size of a SD Card.

I have an old Kingston 64MB SD-Card and lately I have noticed this kernel message when I use the card:

mmc0: SD Status: Invalid Allocation Unit size.

This is due to the following commit:

commit b63b5e819d5b21ae493c17c356018ffa98d3ee1c
Author: Alan Cox <[email protected]>
Date:   Mon Jul 2 18:55:13 2012 +0100

    mmc: core: correct invalid error checking

From the "SD Specifications, Part 1, Physical Layer Specification",

* AU_SIZE
This 4-bit field indicates AU Size and the value can be selected from 16 KB.

  AU_SIZE  Value Definition
  -------  ----------------
    0h     Not Defined
    1h     16 KB
    2h     32 KB
    3h     64 KB
    4h     128 KB
    5h     256 KB
    6h     512 KB
    7h     1 MB
    8h     2 MB
    9h     4 MB
    Ah     8 MB
    Bh     12 MB
    Ch     16 MB
    Dh     24 MB
    Eh     32 MB
    Fh     64 MB

Also in the specification is this note:

Sector: is the unit that is related to the erase commands. Its size is the number of blocks that will be erased in one portion. The size of a sector is fixed for each device. The information about the sector size (in blocks) is stored in the CSD. Note that if the card specifies AU size, sector size should be ignored.

And this:

* SECTOR_SIZE
This field is fixed to 7Fh, which indicates 64 KBytes. This value does not relate to erase operations. High Capacity and Extended Capacity cards indicate memory boundary by AU size and this field should not be used.

So, if an au size of 0 is reported wouldn't the erase size be the sector size? If nothing else I think the test needs to be adjusted to not report the error for an au size of 0.

Regards,
Hartley