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SubjectRe: [PATCH 06/27] ARM: EXYNOS:: Enter a15 lowpower mode for Exynos3250 based on Cortex-a7
On 04/10/2014 09:07 PM, Marc Zyngier wrote:
> 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.
>

Thanks for your review.

Best Regards,
Chanwoo Choi



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