On Thu, 30 Sep 2010, Chris Ball wrote:
> Hi Jaehoon/Adrian,
>
> On Thu, Sep 16, 2010 at 03:46:50PM +0900, Jaehoon Chung wrote:
> > Hi all,
> > This is a RFC patch that support clock-gating for saving power consumption.
> > I found mmc_host_enable/mmc_host_disable function in core.c
> > (using MMC_CAP_DSIABLE. i think that use when host enable/disable)
> > So, i used that functions and implemented some functions in sdhci-s3c.c & sdhci.c
> >
> > i want any feedback. how do you think about this patch?
> > Plz let me know...
>
> A few points:
> * Have you tested this patch? Did you see a decrease in power
> consumption? How large was the decrease?
> * I don't understand exactly how/when you're expecting to save power
> with this approach of defining .{enable,disable}() without then
> calling them from your driver code. Under which circumstances do
> you think this will power down the clock?
> * CC'ing Adrian for help with review, since he wrote these callbacks.
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.
Nicolas
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