Re: Re: [RFC] mmc: core: Set clock before switching to highspeed mode.

[Hans de Goede <hdegoede-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>]

Hi,

On 08-09-15 17:38, Yousong Zhou wrote:
> I just tried a method from allwinner's u-boot sources: retry the mode switch in
> case of an error [1].  It was accompanied with a comment quoted below:
>
> //retry for Toshiba emmc;for the first time Toshiba emmc change to HS
> //it will return response crc err,so retry
>
> Well, that 1GB card of mine is labeled as "pqi" made in Korea.  This workaround
> really worked and it succeeded on the second try, though I am not sure how
> anti-spec this can be (the spec says a power reset SHOULD be done in the case
> of crc error in the status data).
>
> The above change alone can make the card work.  I also noticed that allwinner's
> uboot will disable the clock first before setting it and re-enable it
> thereafter [2].  I can only guess that this is possibly some bugfix made
> by engineers of allwinner.  So I mimicked this approach and attached a patch
> here.

Thanks for this. So if I understand you correctly then just the:

"mmc: retry in the case of failing to switch to HS mode"

Patch is enough to make things work, right ?

That makes sense because the clock dance you are subscribing is something which
allwinner does in many places and it really is not necessary.

Can you do a similar patch for the kernel and test that too ?

And once you've a working kernel patch submit that to Ulf, with the mmc
list in the Cc?

If Ulf is willing to take this fix on the kernel side (I'm the sunxi-mmc maintainer
in the kernel, and the fix will get my ack), then I'm willing to take the u-boot
version of this fix.

Regards,

Hans