Re: [PATCH v2 2/6] of: Add helper for mapping device node to logical CPU number

[Suzuki K Poulose]

On 24/07/17 17:42, Sudeep Holla wrote:
> On 24/07/17 11:29, Suzuki K Poulose wrote:
> > Add a helper to map a device node to a logical CPU number to avoid
> > duplication. Currently this is open coded in different places (e.g
> > gic-v3, coresight). The helper tries to map device node to a "possible"
> > logical CPU id, which may not be online yet. It is the responsibility
> > of the user to make sure that the CPU is online. The helper uses
> > of_get_cpu_node() which uses arch specific backends to match the phyiscal
> > ids.
> >
> > Cc: Rob Herring <robh+dt@xxxxxxxxxx>
> > Cc: Mark Rutland <mark.rutland@xxxxxxx>
> > Signed-off-by: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
> > ---
> >  drivers/of/base.c         | 26 ++++++++++++++++++++++++++
> >  include/linux/of_device.h |  7 +++++++
> >  2 files changed, 33 insertions(+)
> >
> > diff --git a/drivers/of/base.c b/drivers/of/base.c
> > index 686628d..639af23 100644
> > --- a/drivers/of/base.c
> > +++ b/drivers/of/base.c
> > @@ -420,6 +420,32 @@ struct device_node *of_get_cpu_node(int cpu, unsigned int *thread)
> >  EXPORT_SYMBOL(of_get_cpu_node);
> >
> >  /**
> > + * of_device_node_get_cpu: Get the logical CPU number for a given device_node
> > + *
> > + * @cpu_node: Pointer to the device_node for CPU.
> > + *
> > + * Returns the logical CPU number of the given CPU device_node.
> > + * Returns >= nr_cpu_ids if CPU is not found.
> > + */
> > +int of_device_node_get_cpu(struct device_node *cpu_node)
> > +{
> > +	int cpu, thread;
> > +	bool found = false;
> > +	struct device_node *np;
> > +
> > +	for_each_possible_cpu(cpu) {
> > +		np = of_get_cpu_node(cpu, &thread);
>
> Ideally, we should be able to use of_cpu_device_node_get instead of
> of_get_cpu_node which parses the device tree. Not sure if that's the
> case here too.
>
> Sorry for following up on this so late. I had a patch in my tree
> for-a-while to address that. Just posted it[1] now seeing this patch now.
>
> You can move to of_cpu_device_node_get if all users of this function are
> called after CPU's are registered. Otherwise, you can keep it as is for
> now and it can be changed once [1] lands.

As you mentioned offline, since GIC uses this, we need to stick to of_get_cpu_node.
In fact, I started off with the of_cpu_device_node_get() and switched to the former.

It would be really nice to have your patch, which streamlines the interface and we
could switch to that.

Cheers
Suzuki

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