Re: [PATCH 3/4] arm: add basic support for Mediatek MT6589 boards

From: Maxime Ripard <maxime.ripard@free-electrons.com>
To: Marc Zyngier <marc.zyngier@arm.com>
Cc: Mark Rutland <Mark.Rutland@arm.com>, Andrew Lunn <andrew@lunn.ch>,
	"linux-doc@vger.kernel.org" <linux-doc@vger.kernel.org>,
	Thierry Reding <thierry.reding@gmail.com>,
	"heiko.stuebner@bq.com" <heiko.stuebner@bq.com>,
	Russell King - ARM Linux <linux@arm.linux.org.uk>,
	Daniel Lezcano <daniel.lezcano@linaro.org>,
	Florian Vaussard <florian.vaussard@epfl.ch>,
	Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>,
	"devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
	Jason Cooper <jason@lakedaemon.net>,
	Pawel Moll <Pawel.Moll@arm.com>,
	Ian Campbell <ijc+devicetree@hellion.org.uk>,
	Rob Herring <robh+dt@kernel.org>,
	Matthias Brugger <matthias.bgg@gmail.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	"linux-arm-kernel@lists.infradead.org"
	<linux-arm-kernel@lists.infradead.org>,
	Randy Dunlap <rdunlap@infradead.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 3/4] arm: add basic support for Mediatek MT6589 boards
Date: Fri, 11 Apr 2014 11:53:03 +0200	[thread overview]
Message-ID: <20140411095303.GV28585@lukather> (raw)
In-Reply-To: <5347B942.2040703@arm.com>

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On Fri, Apr 11, 2014 at 10:43:30AM +0100, Marc Zyngier wrote:
> On 11/04/14 10:11, Matthias Brugger wrote:
> > 2014-04-10 11:01 GMT+02:00 Marc Zyngier <marc.zyngier@arm.com>:
> >> A couple of things on top of Rob's comments:
> >>
> >> On Wed, Apr 09 2014 at 10:50:33 pm BST, Rob Herring <robherring2@gmail.com> wrote:
> >>> On Wed, Apr 9, 2014 at 2:45 PM, Matthias Brugger <matthias.bgg@gmail.com> wrote:
> >>>> This adds a generic devicetree board file and a dtsi for boards
> >>>> based on the MT6589 SoCs from Mediatek.
> >>>>
> >>>> Apart from the generic parts (gic, clocks) the only component
> >>>> currently supported are the timers.
> >>>>
> >>>> Signed-off-by: Matthias Brugger <matthias.bgg@gmail.com>
> >>
> >> [...]
> >>
> >>>> diff --git a/arch/arm/mach-mediatek/Kconfig b/arch/arm/mach-mediatek/Kconfig
> >>>> new file mode 100644
> >>>> index 0000000..c0139ca
> >>>> --- /dev/null
> >>>> +++ b/arch/arm/mach-mediatek/Kconfig
> >>>> @@ -0,0 +1,14 @@
> >>>> +config ARCH_MEDIATEK
> >>>> +       bool "Mediatek MT6589 SoC" if ARCH_MULTI_V7
> >>>> +       select ARCH_REQUIRE_GPIOLIB
> >>>
> >>> Then where is your GPIO driver?
> >>>
> >>>> +       select ARM_GIC
> >>>> +       select CACHE_L2X0
> >>>> +       select HAVE_ARM_TWD if LOCAL_TIMERS
> >>
> >> Hell no! ;-) ARM_ARCH_TIMER is the way (please also add the missing
> >> node).
> > 
> > I considered this, but the timer wasn't able to get it's clock frequency:
> > "Architected timer frequency not available
> > Division by zero in kernel."
> 
> This is because your bootloader/firmware is utterly broken, and doesn't
> set CNTFRQ (it must be set on all CPUs, from secure mode). As a
> *workaround*, you can set the timer frequency in the timer node, but
> that's just a hack, and will prevent virtual machines from running on
> such hardware.

Is it?

From what I understood from ARM's ARM, CNTFRQ must be set during the
system boot, but even though the arch timer driver can fetch the
frequency from clock-frequency, I don't see anywhere that it actually
writes to CNTFRQ whatever it retrieved.

But I'm probably missing something here...

Maxime

-- 
Maxime Ripard, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com

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