linux-kernel - Re: [PATCH v2 5/6] clocksource: Add a new timer-ingenic driver

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Message-ID: <20180103210840.hsh4kghuxz7btu5f@rob-hp-laptop>
Date:   Wed, 3 Jan 2018 15:08:40 -0600
From:   Rob Herring <robh@...nel.org>
To:     Paul Cercueil <paul@...pouillou.net>
Cc:     Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...eaurora.org>,
        Mark Rutland <mark.rutland@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Jason Cooper <jason@...edaemon.net>,
        Marc Zyngier <marc.zyngier@....com>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Lee Jones <lee.jones@...aro.org>, linux-clk@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 5/6] clocksource: Add a new timer-ingenic driver

On Mon, Jan 01, 2018 at 03:33:43PM +0100, Paul Cercueil wrote:
> This driver will use the TCU (Timer Counter Unit) present on the Ingenic
> JZ47xx SoCs to provide the kernel with a clocksource and timers.
> 
> Signed-off-by: Paul Cercueil <paul@...pouillou.net>
> ---
>  .../devicetree/bindings/timer/ingenic,tcu.txt      |  35 +++

Separate patch please.

>  drivers/clocksource/Kconfig                        |   8 +
>  drivers/clocksource/Makefile                       |   1 +
>  drivers/clocksource/timer-ingenic.c                | 256 +++++++++++++++++++++
>  4 files changed, 300 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/timer/ingenic,tcu.txt
>  create mode 100644 drivers/clocksource/timer-ingenic.c
> 
>  v2: Use SPDX identifier for the license
> 
> diff --git a/Documentation/devicetree/bindings/timer/ingenic,tcu.txt b/Documentation/devicetree/bindings/timer/ingenic,tcu.txt
> new file mode 100644
> index 000000000000..e4944972ea53
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/timer/ingenic,tcu.txt
> @@ -0,0 +1,35 @@
> +Ingenic JZ47xx SoCs Timer/Counter Unit driver
> +---------------------------------------------
> +
> +Required properties:
> +
> +- compatible : should be "ingenic,<socname>-tcu". Valid strings are:
> +  * ingenic,jz4740-tcu
> +  * ingenic,jz4770-tcu
> +  * ingenic,jz4780-tcu
> +- interrupt-parent : phandle of the TCU interrupt controller.
> +- interrupts : Specifies the interrupts the controller is connected to.
> +- clocks : List of phandle & clock specifiers for the TCU clocks.
> +- clock-names : List of name strings for the TCU clocks.
> +- ingenic,channels: a list of TCU channels to be used as timers.

Why is this needed? This looks like you are trying to assign certain 
timers to clocksource and clockevent. A common problem, but one that 
should be decided by describing h/w features. There must be some 
property present or missing to make you decide to use a given channel or 
not.

> +
> +Example:
> +
> +/ {
> +	regmap {
> +		compatible = "simple-mfd", "syscon";
> +		reg = <0x10002000 0x1000>;
> +
> +		tcu: timer {
> +			compatible = "ingenic,jz4740-tcu";
> +
> +			clocks = <&tcu 0>, <&tcu 1>;
> +			clock-names = "timer0", "timer1";

It's curious that you have timer0 and timer1 here and then channels 0 
and 1 below. Would your clocks change if you use channel 2 for example? 
The binding should be a list of clock connections in the h/w, not 
just what the driver needs or what the used h/w configuration is. 

Rob