Re: [BUG/RFC] SDHCI_QUIRK_NO_MULTIBLOCK for i.MX35/25

[Steffen Trumtrar <s.trumtrar@pengutronix.de>]

On Fri, Nov 15, 2013 at 10:15:37AM +0100, Steffen Trumtrar wrote:
> Hi!
> 
> 
> 1 Actual Use-Case
> =================
> 
>   I have a SDIO card with a Marvell 8787, that works fine on an i.MX53
>   with the drivers/net/wireless/mwifiex/sdio.c driver. On an i.MX35
>   however the loading of the firmware errors out on the very first
>   single-block transfer with 1024 bytes payload.
> 
> 
> 2 Reason for failure
> ====================
> 
>   sdhci defines SDHCI_QUIRK_NO_MULTIBLOCK to completely disable
>   multi-block transfers for a host. The max_blk_count is simply set to 1
>   to achieve this. Currently only i.MX35 and i.MX25 seem to be the only
>   users of that quirk.  The quirk is used to fix an errata on these
>   SoCs, that says, that "CMD12 abort operation does not abort data
>   transfer on AHB". (ENGcm07207)
> 
>   So, this is a problem regarding only SD and not SDIO.  On this special
>   SDIO card, it looks like multi-block transfer has to be used for
>   anything >16 bytes. Removing the quirk fixes the firmware loading
>   error. The device is detected successfully after loading and can
>   connect to an AP.
> 
> 
> 3 Question
> ==========
> 
>   And here comes the question: What would be the correct approach to fix
>   that and differentiate those two cases, so that we can use multi-block
>   transfers with CMD53 but not with CMD25(?!) ?
> 
>   1a. As I see no other users of that quirk, it might be okay to rename
>       it, to better reflect the actual problem it fixes (broken CMD12 or
>       something).
> 
>   1b. When the host knows with what it deals with (SDIO or SD) set the
>       max_blk_count according to the quirk. And only in the SD case, that is.
> 
>   or
> 
>   2. Introduce a max_blk_count_sd and max_blk_count_sdio and use them
>      everywhere. Seems rather invasive and over the top.
> 
>   or
> 
>   3. something better.
> 
> 

Ping...

Regards,
Steffen


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