RE: [RFC PATCH 1/1 v8]mmc: Support-FFU-for-eMMC-v5.0

[Alex Lemberg <Alex.Lemberg@sandisk.com>]

[snip]

> My conclusion from that is (correct me if I am wrong, since it may be vendor
> specific), that only minor modifications should be needed to the mmc ioctl. We
> need to add special treatment for when "cmd.opcode ==
> MMC_FFU_DOWNLOAD_OP". In such scenario the following sequence needs to
> be maintained.
> 
> 1. Claim host etc.
> 2. Set FFU mode.
> 3. Write some sectors to the FFU area, but in the same way as any other mmc
> ioctl WRITE is done.
> 4. Set normal mode.
> 5. Relase host etc.
> 
> That sequence then needs to be repeated to write the complete firmware,
> depending on buffer size. Between each and every piece of FFU data that is
> written, normal READ/WRITE operations can be served.
> Right?

We checked again the current IOCTL implementation, and we see issues
In implementing FFU as suggested above:

1. No support for multiple Write operations.
    For running Multiple I/O, user need to send CMD23 or CMD12.
    So structures "sbc" or "stop" of "mmc_blk_request" should be set accordingly.

2. There is a limit in chunk size in current implementation of IOCTL.
     From some reason we can't write more than 64KB on our platform,
     Although, the MMC_IOC_MAX_BYTES is defined to be 128KB

Based on this, we think that using existing IOCTL implementation is not 
a good solution for FFU.


Thanks,
Alex