Re: [RFC RESEND] sdhci-s3c: support clock enable/disable (clock-gating)

[Chris Ball <cjb@laptop.org>]

Hi,

On Wed, Sep 29, 2010 at 11:42:01PM -0400, Nicolas Pitre wrote:
> As I already said here: 
> 
> 	http://article.gmane.org/gmane.linux.ports.arm.omap/39411
> 
> I find those callbacks rather problematic.  Currently, 
> mmc_host_disable() is called by the host driver (currently OMAP) and 
> that's wrong.  Such decision cannot be made in the controller driver -- 
> it has to be made higher up the stack.

I strongly agree.  I hadn't noticed that aspect of this design until
today.  It looked like Linus W had a nice core-integrated clocking
framework almost ready to go a year ago, but it lost out.  (Something
left to do was to give extra time after a request in case we're on a
broken card which requires the card clock to be present during its
writeback.)

I'm not sure where to go from here -- advice welcome.  It would
perhaps be ideal if Linus W and Adrian could work together to make
the current framework look more like Linus' original intent and then
move omap_hsmmc to it as painlessly as possible.  Of course I wouldn't
expect this to happen quickly.

In the meantime, I would suggest that we should not accept any more
users of this framework, which would be a NACK to Jaehoon's patch
(which appears to my reading not to achieve any power-saving anyway).

Adrian, I'm sorry that I'm suggesting reverting -- or at least strongly
modifying -- a framework after it's already shipped in a release; if
you think this is unreasonable, I'll consider your argument carefully.

Thanks,

-- 
Chris Ball   <cjb@laptop.org>   <http://printf.net/>
One Laptop Per Child