Hi Dinh, Linus,
On Fri, 2019-08-23 at 10:42 -0500, Dinh Nguyen wrote:
>
> On 8/23/19 4:19 AM, Linus Walleij wrote:
> > On Tue, Aug 20, 2019 at 4:58 PM Dinh Nguyen <dingu...@kernel.org> wrote:
> >
> > > @@ -401,6 +402,26 @@ static int amba_device_try_add(struct amba_device
> > > *dev, struct resource *parent)
> > > ret = amba_get_enable_pclk(dev);
> > > if (ret == 0) {
> > > u32 pid, cid;
> > > + int count;
> > > + struct reset_control *rstc;
> > > +
> > > + /*
> > > + * Find reset control(s) of the amba bus and de-assert
> > > them.
> > > + */
> > > + count = reset_control_get_count(&dev->dev);
The reset_control_get_count() inline stub returns -ENOENT, so the
compiler can throw away the complete loop.
> > > + while (count > 0) {
> > > + rstc =
> > > of_reset_control_get_shared_by_index(dev->dev.of_node, count - 1);
Since resets are looked up with of_reset_control_get, I'd use
of_reset_control_get_count() above for consistency. But see below:
> > > + if (IS_ERR(rstc)) {
> > > + if (PTR_ERR(rstc) == -EPROBE_DEFER)
> > > + ret = -EPROBE_DEFER;
> > > + else
> > > + dev_err(&dev->dev, "Can't get
> > > amba reset!\n");
> > > + break;
> > > + }
> > > + reset_control_deassert(rstc);
> > > + reset_control_put(rstc);
> > > + count--;
> > > + }
It looks like the order of deassertions is irrelevant. If so,
You can use of_reset_control_array_get() to simplify this:
+ rstc =
of_reset_control_array_get_optional_shared(dev->dev.of_node);
+ if (IS_ERR(rstc)) {
+ if (PTR_ERR(rstc) != -EPROBE_DEFER)
+ dev_err(&dev->dev, "Can't get amba reset!\n");
+ return PTR_ERR(rstc);
+ }
+ reset_control_deassert(rstc);
+ reset_control_put(rstc);
> > I'm not normally a footprint person, but the looks of the stubs in
> > <linux/reset.h> makes me suspicious whether this will have zero impact
> > in size on platforms without reset controllers.
> >
> > Can you just ls -al on the kernel without CONFIG_RESET_CONTROLLER
> > before and after this patch and ascertain that it has zero footprint effect?
>
> Thanks for the review. I checked it, and indeed, it does have a zero
> footprint effect.
>
> >
> > If it doesn't I'd sure like to break this into its own function and
> > stick a if (!IS_ENABLED(CONFIG_RESET_CONTROLLER)) return 0;
> > in there to make sure the compiler drops it.
> >
> > Also it'd be nice to get Philipp's ACK on the semantics, though they
> > look correct to me.
regards
Philipp
