[U-Boot] [PATCH v2 1/9] sunxi: initial sun7i clocks and timer support.

[Ian Campbell]

On Thu, 2014-03-27 at 23:36 +0100, Marek Vasut wrote:
> On Thursday, March 27, 2014 at 11:12:38 PM, Ian Campbell wrote:
> > On Thu, 2014-03-27 at 23:00 +0100, Marek Vasut wrote:
> > > On Thursday, March 27, 2014 at 10:29:56 PM, Ian Campbell wrote:
> > > > On Mon, 2014-03-24 at 21:52 +0100, Marek Vasut wrote:
> > > > > > +static struct sunxi_timer *timer_base =
> > > > > > +     &((struct sunxi_timer_reg
> > > > > > *)SUNXI_TIMER_BASE)->timer[TIMER_NUM]; +
> > > > > > +/* macro to read the 32 bit timer: since it decrements, we invert
> > > > > > read value */ +#define READ_TIMER() (~readl(&timer_base->val))
> > > > > 
> > > > > This macro has to go, just use ~readl() in place. But still, why do
> > > > > you use that negation in "~readl()" anyway ?
> > > > 
> > > > The comment right above it explains why: the timer counts backwards and
> > > > inverting it accounts for that.
> > > > 
> > > > This is subtle enough that I don't think using ~readl() in place in the
> > > > 3 callers would be an improvement.
> > > 
> > > Please do it, we don't want any implementers down the line using this
> > > "READ_TIMER()" call and getting hit by "timer_base undefined" . That
> > > macro hides the dependency on this symbol, while if you expanded it
> > > in-place, the dependency would be explicit. I really do want to see that
> > > macro gone, sorry.
> > 
> > How about a static inline instead of the macro? I'm thinking with a
> > body:
> > {
> >       struct sunxi_timer *timers =
> >               (struct sunxi_timer_reg *)SUNXI_TIMER_BASE;
> >       return timers[TIMER_NUM]->val;
> > }
> > With something similar in timer_init then both the macro and the static
> > global timer_base can be dropped.
> 
> That's just wrapping a readl() into another function, which seems unnecessary 
> really.

Sorry, but I think inlining the readl (and along with it the
interesting/subtle) inverting functionality is a terrible idea, it
should be wrapped in some sort of accessor precisely because it is not a
raw readl.

I'm going to make it a function as I suggested.

> > BTW this macro is in arch/arm/cpu/armv7/sunxi/timer.c not a header, so
> > I'm not sure which implementers down the line you were worried about
> > using it in some other context where it breaks.
> 
> People plumbing in the timer.c file who are not aware the macro has a dependency 
> which is not passed as it's parameter.

What people? What plumbing? I've no idea what you are concerned about
here.

Ian.