Re: [PATCH] mmc: renesas_sdhi: use extra flag for CBSY usage

[Wolfram Sang <wsa@the-dreams.de>]

[-- Attachment #1: Type: text/plain, Size: 1236 bytes --]

On Thu, Aug 10, 2017 at 09:58:50AM +0200, Simon Horman wrote:
> On Wed, Aug 09, 2017 at 09:00:41PM +0200, Wolfram Sang wrote:
> > There is one SDHI instance on Gen2 which does not have the CBSY bit.
> > So, turn CBSY usage into an extra flag and set it accordingly. This has
> > the additional advantage that we can also set it for other incarnations
> > later.
> 
> What is the run-time effect, if any, of this change?

The run-time effect is that a few cycles are saved because CBSY signals
ready a bit earlier than SCLKDIVEN. Though, the more important aspect is
that docs explicitly say to wait for CBSY. That's why this change was
requested although I don't think it will matter much in practice.

> > Chris: according to the specs I have, we can enable it for RZ as well. I'll
> > send a patch for that in a minute. If you could test this on top of this one,
> > that would be much appreciated! Thanks.
> 
> I take it from the above you did a pass of the available documentation to
> see which SoCs support this feature. If so, thanks!

I don't have docs for R-Car Gen1 SDHI. But given that even Gen2 has one
SDHI instance without CBSY and Gen1 is older, my educated guess is that
it does not have CBSY.


[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 833 bytes --]