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 19:25:00 +0900 [thread overview]
Message-ID: <188e01d10021$41b88eb0$c529ac10$@kernel.org> (raw)
In-Reply-To: <187701d1001f$284b1350$78e139f0$@kernel.org>
Kukjin Kim wrote:
>
> 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...
>
Oops, it should be 5440 not 5410. Could be "you see it looks work well", but it
is not guaranteed...unfortunately...
> - Kukjin
prev parent reply other threads:[~2015-10-06 10:25 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
2015-10-06 10:16 ` Pavel Fedin
2015-10-06 10:25 ` Kukjin Kim [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to='188e01d10021$41b88eb0$c529ac10$@kernel.org' \
--to=kgene@kernel$(echo .)org \
--cc=linux-arm-kernel@lists$(echo .)infradead.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox