From: Arnd Bergmann <arnd@arndb.de>
To: Srinivas KANDAGATLA <srinivas.kandagatla@st.com>
Subject: Re: [RFC 2/8] ARM:global_timer: Add ARM global timer support.
Date: Wed, 8 May 2013 16:38:22 +0200
User-Agent: KMail/1.12.2 (Linux/3.8.0-18-generic; KDE/4.3.2; x86_64; ; )
Cc: linux@arm.linux.org.uk, will.deacon@arm.com, Rob Landley <rob@landley.net>,
        Grant Likely <grant.likely@secretlab.ca>,
        Rob Herring <rob.herring@calxeda.com>,
        Samuel Ortiz <sameo@linux.intel.com>,
        Linus Walleij <linus.walleij@linaro.org>,
        "Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
        Jiri Slaby <jslaby@suse.cz>, Stuart Menefy <stuart.menefy@st.com>,
        Shawn Guo <shawn.guo@linaro.org>, Olof Johansson <olof@lixom.net>,
        Jason Cooper <jason@lakedaemon.net>,
        Stephen Warren <swarren@nvidia.com>,
        Maxime Ripard <maxime.ripard@free-electrons.com>,
        Nicolas Pitre <nico@linaro.org>, Dave Martin <dave.martin@linaro.org>,
        Marc Zyngier <marc.zyngier@arm.com>,
        Viresh Kumar <viresh.kumar@linaro.org>,
        Mark Brown <broonie@opensource.wolfsonmicro.com>,
        Dong Aisheng <dong.aisheng@linaro.org>, linux-doc@vger.kernel.org,
        linux-kernel@vger.kernel.org, devicetree-discuss@lists.ozlabs.org,
        linux-arm-kernel@lists.infradead.org, linux-serial@vger.kernel.org
References: <1368022187-1633-1-git-send-email-srinivas.kandagatla@st.com> <1368022260-2197-1-git-send-email-srinivas.kandagatla@st.com>
In-Reply-To: <1368022260-2197-1-git-send-email-srinivas.kandagatla@st.com>
MIME-Version: 1.0
Content-Type: Text/Plain;
  charset="iso-8859-15"
Content-Transfer-Encoding: 7bit
Message-Id: <201305081638.23100.arnd@arndb.de>
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 2581
Lines: 56

On Wednesday 08 May 2013, Srinivas KANDAGATLA wrote:
> From: Stuart Menefy <stuart.menefy@st.com>
> 
> This is a simple driver for the global timer module found in the Cortex
> A9-MP cores from revision r1p0 onwards. This should be able to perform
> the functions of the system timer and the local timer in an SMP system.
> 
> The global timer has the following features:
>     The global timer is a 64-bit incrementing counter with an
> auto-incrementing feature. It continues incrementing after sending
> interrupts. The global timer is memory mapped in the private memory
> region.
>     The global timer is accessible to all Cortex-A9 processors in the
> cluster. Each Cortex-A9 processor has a private 64-bit comparator that
> is used to assert a private interrupt when the global timer has reached
> the comparator value. All the Cortex-A9 processors in a design use the
> banked ID, ID27, for this interrupt. ID27 is sent to the Interrupt
> Controller as a Private Peripheral Interrupt. The global timer is
> clocked by PERIPHCLK.
> 
> Signed-off-by: Stuart Menefy <stuart.menefy@st.com>
> Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@st.com>
>

Are you sure we don't already have a driver for this? It sounds unlikely
that you are the first one to do this when the hardware is so common.

>  Documentation/devicetree/bindings/arm/gt.txt |   21 ++
>  arch/arm/Kconfig                             |    6 +
>  arch/arm/include/asm/global_timer.h          |   12 +
>  arch/arm/kernel/Makefile                     |    1 +
>  arch/arm/kernel/global_timer.c               |  325 ++++++++++++++++++++++++++
>  5 files changed, 365 insertions(+), 0 deletions(-)
>  create mode 100644 Documentation/devicetree/bindings/arm/gt.txt
>  create mode 100644 arch/arm/include/asm/global_timer.h
>  create mode 100644 arch/arm/kernel/global_timer.c

Move it into drivers/clocksource?
 
> diff --git a/arch/arm/include/asm/global_timer.h b/arch/arm/include/asm/global_timer.h
> new file mode 100644
> index 0000000..46f9188
> --- /dev/null
> +++ b/arch/arm/include/asm/global_timer.h
> @@ -0,0 +1,12 @@
> +int __init global_timer_init(void __iomem *base, unsigned int timer_irq);

I don't see a need to call this from platform code for non-DT platforms, it
can easily be used with CLOCKSOURCE_OF_DECLARE() all the time I think.

	Arnd
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/