Re: [PATCH] sdio: add MMC_CAP_VDD_165_195 host capability

Philip Langdale
2009-10-13T02:41:03Z

On Mon, 12 Oct 2009 14:11:29 +0100
David Vrabel <david.vrabel@csr.com> wrote:

>
> In the 3.00 spec, OCR bit 24 is S18R (Signalling 1.8V request). This
> is outside of the VDD region (bits 0:23). So I think we can support
> non standard DS/HS (Default Speed/High Speed) cards that report 1.8V
> operation (in the VDD region) and new UHS-I (Ultra High Speed phase I)
> cards without any confusion.
>
> On a UHS-I capable controller, the software would send ACMD41 with
> S18R set and see if the card responses with it set. If so, it tells
> the card to switch to 1.8V signalling (CMD11) and tells the
> controller to switch to 1.8V signalling and SDR12 mode. The
> controller still supplies 3.3V to the card even after the switch.
> Later on the host software will query the card to find out what UHS-I
> modes are supported and switch card and controller to a faster mode
> (if possible).

Interesting. But that means that Ohad's patch doesn't make much sense;
his uses the MMC low voltage OCR bit in an SDIO context. So either, the
patch is wrong, or he's dealing with out-of-spec hardware.

Ohad?

--phil