On 14/08/13 12:37, Benjamin Herrenschmidt wrote:

On Wed, 2013-08-14 at 11:01 +0100, Sudeep KarkadaNagesha wrote:

quoted

Yes this doesn't cover the historical "ibm,ppc-interrupt-server#s",
for
which we can have PPC specific wrapper above the generic one i.e. get
the cpu node and then parse for thread id under custom property.

A wrapper is wrong. I don't want to have to have all ppc callers to use
a different function.

Ok.

On the side note the main intention of this patch series[1] is to avoid
calling of_get_cpu_node function once CPU devices are registered. It
initialises the of_node in all the cpu devices using this function when
registering the CPU device. It can be retrieved from cpu_dev->of_node.
So direct users of of_get_cpu_node can be reduced to avoid unnecessary
parsing of DT to find cpu node.

As I said, just make a generic one that returns a thread ID, ie, same
signature as the powerpc one. Make it weak, we can override it in
powerpc-land,

IMO, making generic definition which adhere to the ePAPR specification
as weak is not so clean.

or we can move the ibm,ppc-interrupt-server#s handling
into the generic one, it won't hurt, but leave the thread_id return
there, it doesn't hurt it will come in handy in a few cases without
causing code duplication.

IMO moving of handling ibm,ppc-interrupt-server#s to generic code under
#ifdef CONFIG_PPC seems to be cleaner approach than weak definitation.

As per my understanding each thread is a different logical cpu.
Each logical cpu is mapped to unique physical id(either present in reg
field or legacy ibm,ppc-interrupt-server#s field). So given a logical
cpu id we can get the cpu node corresponding to it.
Looking @ smp_setup_cpu_maps in arch/powerpc/kernel/setup-common.c
and the comment in the same file: "This implementation only supports
power of 2 number of threads.." the thread id id is implicit in the
logical cpu id. Do we need to fetch that from DT ?

Regards,
Sudeep

[1] https://lkml.org/lkml/2013/7/22/219