linux-kernel - Re: [RESEND PATCH v3] clocksource: exynos_mct: Add the support for Exynos 64bit SoC

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Date:	Wed, 14 Jan 2015 17:02:03 +0100
From:	Daniel Lezcano <daniel.lezcano@...aro.org>
To:	Kukjin Kim <kgene@...nel.org>, Chanwoo Choi <cw00.choi@...sung.com>
CC:	tglx@...utronix.de, inki.dae@...sung.com,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-samsung-soc@...r.kernel.org,
	Kukjin Kim <kgene.kim@...sung.com>,
	Mark Rutland <mark.rutland@....com>,
	Doug Anderson <dianders@...omium.org>,
	'Olof Johansson' <olof@...om.net>
Subject: Re: [RESEND PATCH v3] clocksource: exynos_mct: Add the support for
 Exynos 64bit SoC

On 01/14/2015 04:51 PM, Kukjin Kim wrote:
> On 01/14/15 14:33, Chanwoo Choi wrote:
>
> Hi,
>
> + Doug, Olof
>
>> This patch adds the support for Exynos 64bit SoC. The delay_timer is only used
>> for Exynos 32bit SoC.
>>
> Yes, the Exynos MCT(Multi-Core Timer) is 64bit timer and it is available
> on 64bit exynos SoC such as exynos7. But basically ARMv8 architecture is
> including ARM ARCH timer (ARM Generic Timer) and exynos7 also has
> implemented it and additionally its access is faster than using memory
> mapped register called SFR for MCT...so Doug submitted patch to use MCT
> on 32bit exynos SoCs before.
>
> I know using MCT on 64bit exynos is usefulness for Power Management and
> I need to talk to relevant guys in office again. If anything, I'll let
> you know.

I will wait for your answer before digging more the patch.

Thanks
   -- Daniel

>> Cc: Daniel Lezcano <daniel.lezcano@...aro.org>
>> Cc: Thomas Gleixner <tglx@...utronix.de>
>> Cc: Kukjin Kim <kgene.kim@...sung.com>
>> Cc: Mark Rutland <mark.rutland@....com>
>> Signed-off-by: Chanwoo Choi <cw00.choi@...sung.com>
>> ---
>> This patch set is tested on 64-bit Exynos SoC. I send only this patch from
>> following patchst[1].
>> [1] https://lkml.org/lkml/2014/12/2/134
>>
>> Changes from v2:
>> - None
>> Changes from v1:
>> - Use CONFIG_ARM instead of CONFIG_ARM64
>>
>>   drivers/clocksource/Kconfig      | 1 -
>>   drivers/clocksource/exynos_mct.c | 4 ++++
>>   2 files changed, 4 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
>> index fc01ec2..be38119 100644
>> --- a/drivers/clocksource/Kconfig
>> +++ b/drivers/clocksource/Kconfig
>> @@ -135,7 +135,6 @@ config CLKSRC_METAG_GENERIC
>>
>>   config CLKSRC_EXYNOS_MCT
>>   	def_bool y if ARCH_EXYNOS
>> -	depends on !ARM64
>>   	help
>>   	  Support for Multi Core Timer controller on Exynos SoCs.
>>
>> diff --git a/drivers/clocksource/exynos_mct.c b/drivers/clocksource/exynos_mct.c
>> index 9403061..b840ea1 100644
>> --- a/drivers/clocksource/exynos_mct.c
>> +++ b/drivers/clocksource/exynos_mct.c
>> @@ -223,6 +223,7 @@ static u64 notrace exynos4_read_sched_clock(void)
>>   	return exynos4_read_count_32();
>>   }
>>
>> +#if defined(CONFIG_ARM)
>>   static struct delay_timer exynos4_delay_timer;
>>
>>   static cycles_t exynos4_read_current_timer(void)
>> @@ -231,14 +232,17 @@ static cycles_t exynos4_read_current_timer(void)
>>   			 "cycles_t needs to move to 32-bit for ARM64 usage");
>>   	return exynos4_read_count_32();
>>   }
>> +#endif
>>
>>   static void __init exynos4_clocksource_init(void)
>>   {
>>   	exynos4_mct_frc_start();
>>
>> +#if defined(CONFIG_ARM)
>>   	exynos4_delay_timer.read_current_timer = &exynos4_read_current_timer;
>>   	exynos4_delay_timer.freq = clk_rate;
>>   	register_current_timer_delay(&exynos4_delay_timer);
>> +#endif
>>
>>   	if (clocksource_register_hz(&mct_frc, clk_rate))
>>   		panic("%s: can't register clocksource\n", mct_frc.name);


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