linux-kernel - Re: [PATCHv2 1/4] Documentation: Add memory mapped ARM architected timer binding

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Message-ID: <516C6F12.5020208@gmail.com>
Date:	Mon, 15 Apr 2013 16:20:18 -0500
From:	Rob Herring <robherring2@...il.com>
To:	Stephen Boyd <sboyd@...eaurora.org>
CC:	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	linux-arm-msm <linux-arm-msm@...r.kernel.org>,
	"devicetree-discuss@...ts.ozlabs.org" 
	<devicetree-discuss@...ts.ozlabs.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCHv2 1/4] Documentation: Add memory mapped ARM architected
 timer binding

On Fri, Apr 12, 2013 at 7:27 PM, Stephen Boyd <sboyd@...eaurora.org> wrote:
> Add a binding for the arm architected timer hardware's memory
> mapped interface. The mmio timer hardware is made up of one base
> frame and a collection of up to 8 timer frames, where each of the
> 8 timer frames can have either one or two views. A frame
> typically maps to a privilege level (user/kernel, hypervisor,
> secure). The first view has full access to the registers within a
> frame, while the second view can be restricted to particular
> registers within a frame. Each frame must support a physical
> timer. It's optional for a frame to support a virtual timer.
>
> Cc: devicetree-discuss@...ts.ozlabs.org
> Cc: Mark Rutland <mark.rutland@....com>
> Cc: Marc Zyngier <Marc.Zyngier@....com>
> Signed-off-by: Stephen Boyd <sboyd@...eaurora.org>
> ---
>  .../devicetree/bindings/arm/arch_timer.txt         | 59 ++++++++++++++++++++--
>  1 file changed, 56 insertions(+), 3 deletions(-)
>
> diff --git a/Documentation/devicetree/bindings/arm/arch_timer.txt b/Documentation/devicetree/bindings/arm/arch_timer.txt
> index 20746e5..ac20cde 100644
> --- a/Documentation/devicetree/bindings/arm/arch_timer.txt
> +++ b/Documentation/devicetree/bindings/arm/arch_timer.txt
> @@ -1,10 +1,14 @@
>  * ARM architected timer
>
> -ARM cores may have a per-core architected timer, which provides per-cpu timers.
> +ARM cores may have a per-core architected timer, which provides per-cpu timers,
> +or a memory mapped architected timer, which provides up to 8 frames with a
> +physical and optional virtual timer per frame.
>
> -The timer is attached to a GIC to deliver its per-processor interrupts.
> +The per-core architected timer is attached to a GIC to deliver its
> +per-processor interrupts via PPIs. The memory mapped timer is attached to a GIC
> +to deliver its interrupts via SPIs.
>
> -** Timer node properties:
> +** CP15 Timer node properties:
>
>  - compatible : Should at least contain one of
>         "arm,armv7-timer"
> @@ -26,3 +30,52 @@ Example:
>                              <1 10 0xf08>;
>                 clock-frequency = <100000000>;
>         };
> +
> +** Memory mapped timer node properties
> +
> +- compatible : Should at least contain "arm,armv7-timer-mem".

Everything about this timer is architecturally defined? If not, let's
use a more specific name.

> +
> +- clock-frequency : The frequency of the main counter, in Hz. Optional.
> +
> +- reg : The control frame base address.
> +
> +Note that #address-cells, #size-cells, and ranges shall be present to ensure
> +the CPU can address a frame's registers.
> +
> +Frame:
> +
> +- frame-number: 0 to 7.

I'd really like to get rid of the frame numbers and sub-nodes. Is the
frame number significant to software?

> +- interrupts : Interrupt list for physical and virtual timers in that order.
> +  The virtual timer interrupt is optional.

Is that optional per frame?

Rob

> +
> +- reg : The first and second view base addresses in that order. The second view
> +  base address is optional.
> +
> +- status : "disabled" indicates the frame is not available for use.
> +
> +Example:
> +
> +       timer@...00000 {
> +               compatible = "arm,armv7-timer-mem";
> +               #address-cells = <1>;
> +               #size-cells = <1>;
> +               ranges;
> +               reg = <0xf0000000 0x1000>;
> +               clock-frequency = <50000000>;
> +
> +               frame@...01000 {
> +                       frame-number = <0>
> +                       interrupts = <0 13 0x8>,
> +                                    <0 14 0x8>;
> +                       reg = <0xf0001000 0x1000>,
> +                             <0xf0002000 0x1000>;
> +               };
> +
> +               frame@...03000 {
> +                       frame-number = <1>
> +                       interrupts = <0 15 0x8>;
> +                       reg = <0xf0003000 0x1000>;
> +                       status = "disabled";
> +               };
> +       };
> --
> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
> hosted by The Linux Foundation
>
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