Re: [PATCH v3 3/8] of/address: Introduce of_dma_get_max_cpu_address()

Nicolas Saenz Julienne
2020-10-15T08:54:20Z

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On Wed, 2020-10-14 at 17:02 -0500, Rob Herring wrote:
> On Wed, Oct 14, 2020 at 2:12 PM Nicolas Saenz Julienne
> <nsaenzjulienne@suse.de> wrote:
> > Introduce of_dma_get_max_cpu_address(), which provides the highest CPU
> > physical address addressable by all DMA masters in the system. It's
> > specially useful for setting memory zones sizes at early boot time.
> >
> > Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
> >
> > ---

[...]

> > + struct of_range_parser parser;
> > + phys_addr_t subtree_max_addr;
> > + struct device_node *child;
> > + phys_addr_t cpu_end = 0;
> > + struct of_range range;
> > + const __be32 *ranges;
> > + int len;
> > +
> > + if (!np)
> > + np = of_root;
> > +
> > + ranges = of_get_property(np, "dma-ranges", &len);
>
> I'm not really following why you changed the algorithm here. You're
> skipping disabled nodes which is good. Was there some other reason?

Yes, it's a little more complex. But I had to change it in order to be able to
start parsing down from an arbitrary device node, which is needed for the unit
tests.

for_each_of_allnodes() and friends will traverse the whole tree, regardless of
the starting point. I couldn't find a similar function that would just iterate
over a subsection of the tree, so I went with this recursive approach.

Regards,
Nicolas

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