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

Open Source and information security mailing list archives

Message-ID: <CAGTfZH0Ve+icxc6FpMJhfNMRMqQASrcUmnrZw-6sYQz8rabC_A@mail.gmail.com>
Date:	Thu, 15 Jan 2015 21:46:32 +0900
From:	Chanwoo Choi <cwchoi00@...il.com>
To:	Mark Rutland <mark.rutland@....com>
Cc:	"linux-samsung-soc@...r.kernel.org" 
	<linux-samsung-soc@...r.kernel.org>,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	Doug Anderson <dianders@...omium.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"inki.dae@...sung.com" <inki.dae@...sung.com>,
	Kukjin Kim <kgene@...nel.org>, Olof Johansson <olof@...om.net>,
	Kukjin Kim <kgene.kim@...sung.com>,
	"tglx@...utronix.de" <tglx@...utronix.de>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [RESEND PATCH v3] clocksource: exynos_mct: Add the support for
 Exynos 64bit SoC

Hi Mark,

On Thu, Jan 15, 2015 at 8:29 PM, Mark Rutland <mark.rutland@....com> wrote:
> On Wed, Jan 14, 2015 at 11:57:00PM +0000, Chanwoo Choi wrote:
>> Hi Kukjin,
>>
>> On 01/15/2015 01:02 AM, Daniel Lezcano wrote:
>> > 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 arch_timer. As you comment, ARCH timer would be used for system timer for ARMv8.
>> But, Exynos5433/Exynos7 (ARMv8) include MCT (Multi-Core Timer) IP. I checked it on
>> Exynos5433/EXynos7 User-manaual and tested it.
>>
>> I think that exynos_mct.c should support the Exynos 64-bit SoC
>> because Exynos5433/Exynos7 include already MCT (Multi-Core Timer) IP.
>>
>> Also, I have a problem to verify ARCH timer on Exynos SoC. Exynos User-manual never includes
>> the detailed information about for ARCH timer(e.g, clock for ARCH timer). I knew that
>> I can get the document of ARCH timer for ARM official site but I think it is insufficient
>> to implement ARCH timer on Exynos SoC.
>
> What do you mean by "insufficient to implement ARCH timer"?

As I knew, timer must need the source clock. The clock for ARCH timer
has dependency on Exynos SoC, But I cannot find

>
> The architected timer is mandatory in ARMv8, and required by the arm64
> kernel.
>
> Additional timers may be requried if you want to put all CPUs into low
> power states where the timer logic may be disabled and/or lose state,
> but regardless the architected timers are necessary.
>
> Thanks,
> Mark.
>
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel@...ts.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives