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

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Date:	Fri, 16 Aug 2013 22:32:31 +1000
From:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:	Sudeep KarkadaNagesha <Sudeep.KarkadaNagesha@....com>
Cc:	"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>,
	"microblaze-uclinux@...e.uq.edu.au" 
	<microblaze-uclinux@...e.uq.edu.au>,
	"linux@...nrisc.net" <linux@...nrisc.net>,
	"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 3/4] powerpc: refactor of_get_cpu_node to support
 other architectures

On Fri, 2013-08-16 at 09:48 +0100, Sudeep KarkadaNagesha wrote:

> > Naming is a bit gross. You might want to make it clearer that
> > we are talking about CPU IDs in the device-tree here.
> > 
> Any particular preference to the name or just a note is sufficient.
> Also unlike PPC, in ARM we don't set hard processor id value based
> values read from device tree. DT must contain the values matching to the
> hardware ID registers.

This is exactly the same on ppc. We don't "set" HW values. The
device-tree content matches the HW internals. Some processors have a
"PIR" register as well which contains the HW value, in this case the
device-tree must contain the same value as the PIR on that processor.

> >> +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;
> >> +		}
> > 
> > Missing:          cell += ac;
> Ah, missed it while refactoring, will fix it. Thanks

Ben.

> 
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