Subject: Re: [v3] Fix missing L2 cache size in /sys/devices/system/cpu

From: Dave Olson <[email-masked]>
Date: Thu, 26 Mar 2015 12:49:14 -0700

Michael Ellerman <[email-masked]> wrote:

> On Thu, 2015-26-02 at 00:04:47 UTC, Dave Olson wrote:
> > @@ -324,14 +335,33 @@ static bool cache_node_is_unified(const struct device_node *np)
> >  	return of_get_property(np, "cache-unified", NULL);
> >  }
> >  
> > +/*
> > + * Handle unified caches that have two different types of tags.  Most embedded
> > + * use cache-size, etc. for the unified cache size, but open firmware systems
> > + * use d-cache-size, etc.   Since they all appear to be consistent, check on
> > + * initialization for which type we are, and use the appropriate structure.
> > + */
> >  static struct cache *cache_do_one_devnode_unified(struct device_node *node,
> >  						  int level)
> >  {
> >  	struct cache *cache;
> > +	int ucache;
> >  
> >  	pr_debug("creating L%d ucache for %s\n", level, node->full_name);
> >  
> >  	cache = new_cache(CACHE_TYPE_UNIFIED, level, node);
>         ^^
> 
> > +	if (of_get_property(node,
> > +		cache_type_info[CACHE_TYPE_UNIFIED_D].size_prop, NULL)) {
> > +		ucache = CACHE_TYPE_UNIFIED_D;
> > +	} else {
> > +		ucache = CACHE_TYPE_UNIFIED; /* assume embedded */
> > +		if (of_get_property(node,
> > +			cache_type_info[CACHE_TYPE_UNIFIED].size_prop, NULL) ==
> > +			NULL)
> > +			printk(KERN_WARNING "Unified cache property missing\n");
> > +	}
> > +
> > +	cache = new_cache(ucache, level, node);
>         ^^
> >  
> >  	return cache;
> >  }
> 
> That looks fishy. You create a cache, and then throw it away and create another
> one and return that. I don't think that's what you intended, is it?

It looks like I missed something when I regenerated the patch, yes.
My version of cacheinfo.c doesn't have the first new_cache() call.

> It would also be cleaner I think if you created another helper, eg.
> cache_is_unified_d() to do the property lookup.

OK.

> And also I don't think you need to do the second property lookup, especially if
> all you're going to do is print a warning.

I wanted to make sure that if a similar issue arose in the future, that
a message was printed so it got caught and fixed.  I don't see a way
to do that without the 2nd lookup.

Let me know what you think, and I'll generate another patch.

Dave Olson
[email-masked]