Re: [PATCH] clocksource/drivers/tango-xtal: Replace code by clocksource_mmio_init

[Daniel Lezcano]

On 11/17/2015 01:48 PM, Marc Gonzalez wrote:
> On 17/11/2015 13:22, Daniel Lezcano wrote:
> > On 11/13/2015 01:20 PM, Marc Gonzalez wrote:
> > > On 13/11/2015 11:58, Daniel Lezcano wrote:
> > >
> > > > The current code to initialize, register and read the clocksource is
> > > > already factored out in mmio.c via the clocksource_mmio_init function.
> > > >
> > > > Factor out the code with the clocksource_mmio_init function.
> > >
> > > The reason I didn't like clocksource_mmio_init() is because it exports
> > > 4 generic accessors.
> > >
> > > I guess this function makes more sense when all platforms are using it,
> > > in an ARCH_MULTIPLATFORM kernel. (Also the accessors are probably quite
> > > small, so the waste is probably minimal.)
> >
> > Hi Marc,
> >
> > it is not clear for me if you agree with this patch or not. Can you
> > clarify ?
>
> [ Adding rmk as the original mmio.c author ]

Good idea. Russell, the patch is https://lkml.org/lkml/2015/11/13/261

> Hello Daniel,
>
> It's hard to give a straight answer. From my limited perspective (building
> a kernel for Sigma boards only) I feel that mmio.c brings nothing. (As you
> mentioned, it would be interesting to measure whether having reg_base in
> the ctx, rather than as a global is better or worse for perf, though the
> actual difference may be lost in the noise.)
>
> On the other hand, I can see how a different perspective, such as yours,
> may see benefits in having all drivers use the same APIs; and there may
> be other savings for ARCH_MULTIPLATFORM builds with lots of platforms.

IMO, if all the drivers are using the same code, then optimizing it will 
benefit to all drivers at the same time.

> I guess if you think it is a good patch, I will defer to your experience.

Ok, I will wait for Russell comments then.

Thanks!

  -- Daniel

> I just wish Thomas would take a look at my mmio patch. I will make an
> official submission, so that it can be properly shot down :-)



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