Messages in this thread | | | Date | Wed, 16 Jul 2014 12:48:48 +0200 | From | Tomasz Figa <> | Subject | Re: [RESEND PATCH v2] ARM: exynos4: hotplug: Fix CPU idle clock down after CPU off |
| |
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
| |