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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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