From: Christopher Covington <cov-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org>
To: Doug Anderson <dianders-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>
Cc: olof-nZhT3qVonbNeoWH0uzbU5w@public.gmane.org,
mark.rutland-5wv7dgnIgG8@public.gmane.org,
devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
Lorenzo Pieralisi
<lorenzo.pieralisi-5wv7dgnIgG8@public.gmane.org>,
Daniel Lezcano
<daniel.lezcano-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>,
pawel.moll-5wv7dgnIgG8@public.gmane.org,
ijc+devicetree-KcIKpvwj1kUDXYZnReoRVg@public.gmane.org,
Marc Zyngier <marc.zyngier-5wv7dgnIgG8@public.gmane.org>,
Stephen Boyd <sboyd-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org>,
Sudeep Holla <Sudeep.Holla-5wv7dgnIgG8@public.gmane.org>,
Will Deacon <will.deacon-5wv7dgnIgG8@public.gmane.org>,
linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
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robh+dt-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org,
Catalin Marinas <Catalin.Marinas-5wv7dgnIgG8@public.gmane.org>,
Nathan Lynch
<Nathan_Lynch-nmGgyN9QBj3QT0dZR+AlfA@public.gmane.org>,
Thomas Gleixner <tglx-hfZtesqFncYOwBW4kG4KsQ@public.gmane.org>,
Sonny Rao <sonnyrao-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>,
linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org
Subject: Re: [PATCH v3] clocksource: arch_timer: Allow the device tree to specify the physical timer
Date: Mon, 29 Sep 2014 09:12:26 -0400 [thread overview]
Message-ID: <54295ABA.1010806@codeaurora.org> (raw)
In-Reply-To: <1410454801-14231-1-git-send-email-dianders-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>
Hi Doug,
On 09/11/2014 01:00 PM, Doug Anderson wrote:
> Some 32-bit (ARMv7) systems are architected like this:
>
> * The firmware doesn't know and doesn't care about hypervisor mode and
> we don't want to add the complexity of hypervisor there.
>
> * The firmware isn't involved in SMP bringup or resume.
>
> * The ARCH timer come up with an uninitialized offset between the
> virtual and physical counters. Each core gets a different random
> offset.
>
> * The device boots in "Secure SVC" mode.
I believe this can safely be detected by whether a write to CNTFRQ succeeds
(handling the UNDEF on failure). I've tested this approach in what I've
determined to be the 19 valid combinations of the following options.
* AArch64 EL3, AArch32 EL3, no EL3
* AArch64 EL2, AArch32 EL2, no EL2
* Start in SVC_N, SVC_S, HYP_N, MON_S
Christopher
--
Employee of Qualcomm Innovation Center, Inc.
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
hosted by the Linux Foundation.
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prev parent reply other threads:[~2014-09-29 13:12 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-09-11 17:00 [PATCH v3] clocksource: arch_timer: Allow the device tree to specify the physical timer Doug Anderson
2014-09-26 10:00 ` Mark Rutland
2014-09-29 17:30 ` Sonny Rao
[not found] ` <CAPz6YkWZWgm--6EJxoV1s3zqTNpAF6+CBOrRc5qxdm5=hFzj1w-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2014-10-01 15:21 ` Doug Anderson
[not found] ` <1410454801-14231-1-git-send-email-dianders-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>
2014-09-29 13:12 ` Christopher Covington [this message]
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