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SubjectRe: [PATCH 06/27] ARM: EXYNOS:: Enter a15 lowpower mode for Exynos3250 based on Cortex-a7
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On Thu, Apr 10 2014 at 11:56:33 am BST, Chanwoo Choi <cw00.choi@samsung.com> wrote:
> On 04/10/2014 06:51 PM, Marc Zyngier wrote:
>> On Thu, Apr 10 2014 at 10:28:23 am BST, Chanwoo Choi <cw00.choi@samsung.com> wrote:
>>> This patch decide proper lowpower mode of either a15 or a9 according to own ID
>>> from Main ID register.
>>>
>>> Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>
>>> Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
>>> ---
>>> arch/arm/mach-exynos/hotplug.c | 13 ++++++++++---
>>> 1 file changed, 10 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/arch/arm/mach-exynos/hotplug.c b/arch/arm/mach-exynos/hotplug.c
>>> index 5eead53..36d3db6 100644
>>> --- a/arch/arm/mach-exynos/hotplug.c
>>> +++ b/arch/arm/mach-exynos/hotplug.c
>>> @@ -135,13 +135,20 @@ void __ref exynos_cpu_die(unsigned int cpu)
>>> int primary_part = 0;
>>>
>>> /*
>>> - * we're ready for shutdown now, so do it.
>>> - * Exynos4 is A9 based while Exynos5 is A15; check the CPU part
>>> + * we're ready for shutdown now, so do it. Exynos4 is A9 based
>>> + * while Exynos5 is A15/Exynos7 is A7; check the CPU part
>>> * number by reading the Main ID register and then perform the
>>> * appropriate sequence for entering low power.
>>> */
>>> asm("mrc p15, 0, %0, c0, c0, 0" : "=r"(primary_part) : : "cc");
>>
>> While you're touching that code, how about using:
>>
>> primary_part = read_cpuid(CPUID_ID);
>
> Or,
> I suggest read_cpuid_part_number() instead of assembler directly.
>
> primary_part = read_cpuid_part_number();

Yup, even better.

>>
>>> - if ((primary_part & 0xfff0) == 0xc0f0)
>>> +
>>> + /*
>>> + * Main ID register of Cortex series
>>> + * - Cortex-a7 : 0x410F_C07x
>>> + * - Cortex-a15 : 0x410F_C0Fx
>>> + */
>>> + primary_part = primary_part & 0xfff0;
>>> + if (primary_part == 0xc0f0 || primary_part == 0xc070)
>>
>> ARM_CPU_PART_CORTEX_A15, ARM_CPU_PART_CORTEX_A7
>
> OK I'll use this defined constant as following:
>
> switch (primary_part)
> case ARM_CPU_PART_CORTEX_A7:
> case ARM_CPU_PART_CORTEX_A15:
> cpu_enter_lowpower_a15();
> break;
> default:
> cpu_enter_lowpower_a9();
> break;
> }

Looks good.

M.
--
Jazz is not dead. It just smells funny.


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