From: kgene@kernel•org (Kukjin Kim)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH 0/2] ARM: EXYNOS: Allow to use architected timer
Date: Tue, 06 Oct 2015 19:09:58 +0900 [thread overview]
Message-ID: <187701d1001f$284b1350$78e139f0$@kernel.org> (raw)
In-Reply-To: <00d801d10014$e6d994a0$b48cbde0$@samsung.com>
Pavel Fedin wrote:
>
> Hello!
>
> > IIRC the use of the CP15 timer is not reliable on this platform.
> > I don't have a link ready, but this has come up a few times.
>
> I know that Samsung SoC guys are not very keen on this, therefore i actually made this optional.
No, it's not a good way and it's not an optional problem...I think, I already
commented many times about that...If we can arch timer on exynos stuff, why we
are still using MCT...? hmm...
> If
> you want, you could omit the second patch, and by default Exynos platform will use MCT. But if
> someone wants to use KVM, it would be enough only to modify device tree in order to enable CP15.
> Would this be a good compromise?
>
No, because the MCT should be used by default _always_ and it is depending on hardware scheme...
> > Regarding KVM usage, would it be possible to emulate the architected
> > timer from qemu instead?
>
> Unfortunately no. Accesses to virtual timer registers cannot be trapped. It is possible to trap
> physical timer accesses, and trick the kernel into using it, but it's slow, and it is a different
> story, which you can read here: http://www.spinics.net/lists/kvm/msg121714.html.
> So, i think that having an option to use CP15 would be a good solution. It is known to work, and i
> use this configuration here on SMDK5410 without any problems.
>
Actually Exynos5410 has been designed differently so it is safe only on smdk5410 not others...
- Kukjin
next prev parent reply other threads:[~2015-10-06 10:09 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-10-06 8:23 [PATCH 0/2] ARM: EXYNOS: Allow to use architected timer Pavel Fedin
2015-10-06 8:23 ` [PATCH 1/2] exynos_mct: Allow to use architected timer mode Pavel Fedin
2015-10-06 8:24 ` [PATCH 2/2] ARM: dts: Use architected timer on Exynos 5410 Pavel Fedin
2015-10-06 8:33 ` Chanwoo Choi
2015-10-06 8:49 ` Pavel Fedin
2015-10-06 8:37 ` [PATCH 0/2] ARM: EXYNOS: Allow to use architected timer Arnd Bergmann
2015-10-06 8:51 ` Alexey Klimov
2015-10-06 8:56 ` Pavel Fedin
2015-10-06 9:12 ` Arnd Bergmann
2015-10-06 9:44 ` Pavel Fedin
2015-10-06 10:03 ` Arnd Bergmann
2015-10-06 10:09 ` Kukjin Kim [this message]
2015-10-06 10:16 ` Pavel Fedin
2015-10-06 10:25 ` Kukjin Kim
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