On Mon 23 Nov 12:17 CST 2020, Wilken Gottwalt wrote:
> On Sat, 21 Nov 2020 23:19:00 -0600
> Bjorn Andersson <bjorn.anders...@linaro.org> wrote:
> > > +static int hwlocks_inuse_show(struct seq_file *seqf, void *unused)
> > > +{
> > > + struct sunxi_hwspinlock_data *priv = seqf->private;
> > > + int inuse;
> > > +
> > > + /* getting the status of only the main 32 spinlocks is supported */
> > > + inuse = hweight32(readl(priv->io_base + SPINLOCK_STATUS_REG));
> >
> > So this returns how many of the locks are taken? How is that useful?
>
> It is a way to see if locks were taken from linux or the arisc core without
> touching the actual hwspinlock abi or the locks. So it is a nice way to debug
> hwspinlocks, hence it is part of debugfs.
>
So in a scenario where two remote processors ping-pong the lock between
them, this will always read 1 and you won't know why?
> > > + seq_printf(seqf, "%d\n", inuse);
[..]
> > > +
> > > + return 0;
> > > +}
> > > +
> > > +static const struct of_device_id sunxi_hwspinlock_ids[] = {
> > > + { .compatible = "allwinner,sun8i-hwspinlock", },
> > > + { .compatible = "allwinner,sun50i-hwspinlock", },
> > > + {},
> > > +};
> > > +MODULE_DEVICE_TABLE(of, sunxi_hwspinlock_ids);
> > > +
> > > +static struct platform_driver sunxi_hwspinlock_driver = {
> > > + .probe = sunxi_hwspinlock_probe,
> > > + .remove = sunxi_hwspinlock_remove,
> > > + .driver = {
> > > + .name = DRIVER_NAME,
> > > + .of_match_table = of_match_ptr(sunxi_hwspinlock_ids),
> >
> > Please avoid of_match_ptr, as this will cause warnings about unused
> > variables when COMPILE_TEST without OF.
>
> So did you mean to leave it out completely?
>
Yes, "worst case" is that you include the reference to
sunxi_hwspinlock_ids on a build without CONFIG_OF and wasting a little
bit of memory.
Using of_match_ptr() with CONFIG_OF=n will result in NULL and as such
we'll get a compile warning that nothing references sunxi_hwspinlock_ids
- so then that will have to be marked __maybe_unused, or wrapped in an
#if...
So better just leave it as:
.of_match_table = sunxi_hwspinlock_ids,
Regards,
Bjorn
