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SubjectRe: [PATCH 2/5] ARM: add SMP support for Broadcom mobile SoCs
On 04/04/2014 01:56 PM, Alex Elder wrote:
> On 04/04/2014 10:30 AM, Tim Kryger wrote:
>> On Thu, Apr 3, 2014 at 7:18 PM, Alex Elder <elder@linaro.org> wrote:
>>
>>> diff --git a/arch/arm/mach-bcm/platsmp.c b/arch/arm/mach-bcm/platsmp.c
>>> new file mode 100644
>>> index 0000000..46a64f2
>>> --- /dev/null
>>> +++ b/arch/arm/mach-bcm/platsmp.c
>>
>>> +/* Size of mapped Cortex A9 SCU address space */
>>> +#define SCU_SIZE 0x58
>>
>>> +/*
>>> + * Enable the Cortex A9 Snoop Control Unit
>>> + *
>>> + * By the time this is called we already know there are multiple
>>> + * cores present. We assume we're running on a Cortex A9 processor,
>>> + * so any trouble getting the base address register or getting the
>>> + * SCU base is a problem.
>>> + *
>>> + * Return 0 if successful or an error code otherwise.
>>> + */
>>> +static int __init scu_a9_enable(void)
>>> +{
>>> + unsigned long config_base;
>>> + void __iomem *scu_base;
>>> +
>>> + if (!scu_a9_has_base()) {
>>> + pr_err("no configuration base address register!\n");
>>> + return -ENXIO;
>>> + }
>>> +
>>> + /* Config base address register value is zero for uniprocessor */
>>> + config_base = scu_a9_get_base();
>>> + if (!config_base) {
>>> + pr_err("hardware reports only one core; disabling SMP\n");
>>> + return -ENOENT;
>>> + }
>>> +
>>> + scu_base = ioremap((phys_addr_t)config_base, SCU_SIZE);
>>> + if (!scu_base) {
>>> + pr_err("failed to remap config base (%lu/%u) for SCU\n",
>>> + config_base, SCU_SIZE);
>>> + return -ENOMEM;
>>> + }
>>> +
>>> + scu_enable(scu_base);
>>> +
>>> + iounmap(scu_base); /* That's the last we'll need of this */
>>> +
>>> + return 0;
>>> +}
>>
>> This function seems useful for Cortex A9 MPCore in general.
>>
>> While you gave it a generic name, you put it in a Broadcom file.
>>
>> Is there a better location for this code?
>
> I think it belongs in arch/arm/kernel/smp_scu.c. I was thinking
> it might be generally useful when I wrote it (hence the more
> complete header comment, for example). And I'll gladly move
> it there, I just didn't want anybody to get hung up on that.

I'm going to re-submit this series this morning. I looked at
where this function might be used, and it looks like only one
other platform could use it (in hi3xxx_smp_prepare_cpus()).
Man of the others define get their scu base address some
other way (using a fixed constant or using device tree).

For now I'm going to keep it where it is. If you or someone else
reiterate the suggestion I'll move it to arch/arm/kernel/smp_scu.c.

-Alex



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