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SubjectRe: [PATCH 06/27] ARM: EXYNOS:: Enter a15 lowpower mode for Exynos3250 based on Cortex-a7
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();

>
>> - 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;
}

>
>> cpu_enter_lowpower_a15();
>> else
>> cpu_enter_lowpower_a9();
>

Best Regards,
Chanwoo Choi




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