linux-kernel - Re: [RFC PATCH v2 3/4] powerpc: refactor of_get_cpu

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Message-ID: <5211EFC7.9090800@arm.com>
Date:	Mon, 19 Aug 2013 11:13:27 +0100
From:	Sudeep KarkadaNagesha <Sudeep.KarkadaNagesha@....com>
To:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
CC:	Sudeep KarkadaNagesha <Sudeep.KarkadaNagesha@....com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
	Jonas Bonn <jonas@...thpole.se>,
	Michal Simek <monstr@...str.eu>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	"grant.likely@...aro.org" <grant.likely@...aro.org>,
	"rob.herring@...xeda.com" <rob.herring@...xeda.com>
Subject: Re: [RFC PATCH v2 3/4] powerpc: refactor of_get_cpu_node to support
 other architectures

On 16/08/13 23:13, Benjamin Herrenschmidt wrote:
> On Fri, 2013-08-16 at 18:39 +0100, Sudeep KarkadaNagesha wrote:
>> +static bool __of_find_n_match_cpu_property(struct device_node *cpun,
>> +                       const char *prop_name, int cpu, unsigned int
>> *thread)
>> +{
>> +       const __be32 *cell;
>> +       int ac, prop_len, tid;
>> +       u64 hwid;
>> +
>> +       ac = of_n_addr_cells(cpun);
>> +       cell = of_get_property(cpun, prop_name, &prop_len);
>> +       if (!cell)
>> +               return false;
>> +       prop_len /= sizeof(*cell);
>> +       for (tid = 0; tid < prop_len; tid++) {
>> +               hwid = of_read_number(cell, ac);
>> +               if (arch_match_cpu_phys_id(cpu, hwid)) {
>> +                       if (thread)
>> +                               *thread = tid;
>> +                       return true;
>> +               }
>> +               cell += ac;
>> +       }
>> +       return false;
>> +}
> 
> The only problem I can see here is if "ac" is not 1, that will not work
> for the ibm,ppc-interrupt-server#s case. IE. The latter is always 1 cell
> per entry, only "reg" depends on #address-cells.
> 
> However that's only a theorical problem since on ppc #address-cells of
> /cpus is always 1...
> 
Ok agreed, but I assume in future if thread ids need 2 ac, it would use
standard 'reg' instead of 'ibm,ppc-interrupt-server#' property.

So I assume the above function is generic and need not be modified to
handle non '1' ac case  with non standard 'ibm,ppc-interrupt-server#'.

Regards,
Sudeep

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