From: t.figa@samsung•com (Tomasz Figa)
To: linux-arm-kernel@lists•infradead.org
Subject: [RESEND PATCH v2] ARM: exynos4: hotplug: Fix CPU idle clock down after CPU off
Date: Wed, 16 Jul 2014 12:48:48 +0200 [thread overview]
Message-ID: <53C65890.8000500@samsung.com> (raw)
In-Reply-To: <1405499003-9975-1-git-send-email-k.kozlowski@samsung.com>
Hi Krzysztof,
Please see my comment below.
On 16.07.2014 10:23, Krzysztof Kozlowski wrote:
> On Exynos4 USE_DELAYED_RESET_ASSERTION must be set in
> ARM_COREx_OPTION register during CPU power down. This is the proper way
> of powering down CPU on Exynos4.
>
> Additionally on Exynos4212 without this the CPU clock down feature won't
> work after powering down some CPU and the online CPUs will work at full
> frequency chosen by CPUfreq governor.
>
> Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung•com>
[snip]
> @@ -36,6 +36,14 @@ static inline void cpu_leave_lowpower(void)
> : "=&r" (v)
> : "Ir" (CR_C), "Ir" (0x40)
> : "cc");
> +
> + if (soc_is_exynos4()) {
> + unsigned int tmp;
> +
> + tmp = __raw_readl(EXYNOS_ARM_CORE_OPTION(core_id));
> + tmp &= ~(S5P_USE_DELAYED_RESET_ASSERTION);
> + __raw_writel(tmp, EXYNOS_ARM_CORE_OPTION(core_id));
> + }
This code is executed only if the CPU doesn't manage to power off before
already receiving a wake-up event. Otherwise the context is lost after
wfi(), as the core power is being cut down.
The normal wake-up path goes through platsmp's exynos_boot_secondary()
and I believe that setting of S5P_USE_DELAYED_RESET_ASSERTION should be
taken care there as well.
Best regards,
Tomasz
next prev parent reply other threads:[~2014-07-16 10:48 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-07-16 8:23 [RESEND PATCH v2] ARM: exynos4: hotplug: Fix CPU idle clock down after CPU off Krzysztof Kozlowski
2014-07-16 10:48 ` Tomasz Figa [this message]
2014-07-16 11:19 ` Krzysztof Kozlowski
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