linux-kernel - Re: [PATCH 10/19] ARM64 / ACPI: Get the enable method for SMP initialization in ACPI way

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Date:	Thu, 31 Jul 2014 18:57:20 +0800
From:	Hanjun Guo <hanjun.guo@...aro.org>
To:	Olof Johansson <olof@...om.net>
CC:	Catalin Marinas <catalin.marinas@....com>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Mark Rutland <mark.rutland@....com>,
	Graeme Gregory <graeme.gregory@...aro.org>,
	Arnd Bergmann <arnd@...db.de>,
	Grant Likely <grant.likely@...aro.org>,
	Sudeep Holla <Sudeep.Holla@....com>,
	Will Deacon <will.deacon@....com>,
	Jason Cooper <jason@...edaemon.net>,
	Marc Zyngier <marc.zyngier@....com>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	Mark Brown <broonie@...aro.org>,
	Robert Richter <rric@...nel.org>,
	Lv Zheng <lv.zheng@...el.com>,
	Robert Moore <robert.moore@...el.com>,
	Lorenzo Pieralisi <Lorenzo.Pieralisi@....com>,
	Liviu Dudau <Liviu.Dudau@....com>,
	Randy Dunlap <rdunlap@...radead.org>,
	Charles.Garcia-Tobin@....com, linux-acpi@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	linaro-acpi-private@...aro.org,
	Tomasz Nowicki <tomasz.nowicki@...aro.org>
Subject: Re: [PATCH 10/19] ARM64 / ACPI: Get the enable method for SMP initialization
 in ACPI way

On 2014-7-31 14:54, Olof Johansson wrote:
> Hi,
> 
> On Thu, Jul 24, 2014 at 09:00:16PM +0800, Hanjun Guo wrote:
>> +/*
>> + * In ACPI mode, the cpu possible map was enumerated before SMP
>> + * initialization when MADT table was parsed, so we can get the
>> + * possible map here to initialize CPUs.
>> + */
> 
> The DT smp init will warn if the kernel has been build with too low NR_CPUS.
> Does the ACPI core already warn, or did that go missing with this separate code
> path?

ACPI code will warn, it is in PATCH 07/19,

+	if (enabled_cpus >=  NR_CPUS) {
+		pr_warn("NR_CPUS limit of %d reached, Processor %d/0x%llx ignored.\n",
+			NR_CPUS, total_cpus, mpidr);
+		return -EINVAL;
+	}

> 
>> +static void __init acpi_smp_init_cpus(void)
>> +{
>> +	int cpu;
>> +
>> +	for_each_possible_cpu(cpu) {
>> +		if (cpu_acpi_read_ops(cpu) != 0)
>> +			continue;
>> +
>> +		cpu_ops[cpu]->cpu_init(NULL, cpu);
>> +	}
>> +}
>> +
>> +void __init smp_init_cpus(void)
>> +{
>> +	if (acpi_disabled)
>> +		of_smp_init_cpus();
>> +	else
>> +		acpi_smp_init_cpus();
> 
> I'm liking these deeply split code paths less and less every time I see
> them. :(
> 
> I would prefer to set up shared state in separate functions, but keep the
> control flow the same. Right now you're splitting it completely.
> 
> I.e. split data setup between the two, but do the loop calling cpu_init()
> the same way. (Yes, that will require you to refactor the DT code path
> a bit too...)

OK, I will dive into the code and figure out if I can fix that as you
suggested, thanks for your comments :)

Best Regards
Hanjun
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