Re: [PATCH 01/12] mmc: sdhci: add support for auto CMD23

Arnd Bergmann
2011-02-18T13:23:18Z

On Friday 18 February 2011, Nath, Arindam wrote:
> > AFAICT, whether CMD23 can be used or not is primarily a decision based
> > on
> > the card, and the block driver might want issue it for a longer range
> > if it needs to split a block request into multiple MMC requests.
>
> Thanks for the comments. Yes, whether a card supports CMD23 depends on
> the card, but Auto CMD23 is a feature added to the Host Controller v3.00
> just like Auto CMD12. I am already doing a check inside
> sdhci_host_auto_cmd23_supported() whether the card supports CMD23, and
> whether the request is for multiple block transfers. Also I tried to make
> my implementation consistent with Auto CMD12 implementation already
> there in the sdhc code.

Ok, I see.

But, assuming that the block driver was changed to always to CMD23 where
appropriate, what is the advantage auf Auto CMD23?

As far as I can tell, changing the block driver would make all hosts
faster, not just sdhci, and it would be able to cover the split requests
I mentioned.

Arnd