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Date:   Tue, 27 Mar 2018 09:46:31 -0500
From:   Rob Herring <robh@kernel.org>
To:     Paul Cercueil <paul@crapouillou.net>
Cc:     Thomas Gleixner <tglx@linutronix.de>,
        Jason Cooper <jason@lakedaemon.net>,
        Marc Zyngier <marc.zyngier@arm.com>,
        Lee Jones <lee.jones@linaro.org>,
        Daniel Lezcano <daniel.lezcano@linaro.org>,
        Ralf Baechle <ralf@linux-mips.org>,
        Jonathan Corbet <corbet@lwn.net>,
        Mark Rutland <mark.rutland@arm.com>,
        James Hogan <jhogan@kernel.org>,
        Maarten ter Huurne <maarten@treewalker.org>,
        linux-clk@vger.kernel.org, devicetree@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-mips@linux-mips.org,
        linux-doc@vger.kernel.org
Subject: Re: [PATCH v4 4/8] dt-bindings: Add doc for the Ingenic TCU drivers
Message-ID: <20180327144631.j2bugsjxulkv57ws@rob-hp-laptop>
References: <20180110224838.16711-2-paul@crapouillou.net>
 <20180317232901.14129-1-paul@crapouillou.net>
 <20180317232901.14129-5-paul@crapouillou.net>
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On Sun, Mar 18, 2018 at 12:28:57AM +0100, Paul Cercueil wrote:
> Add documentation about how to properly use the Ingenic TCU
> (Timer/Counter Unit) drivers from devicetree.
> 
> Signed-off-by: Paul Cercueil <paul@crapouillou.net>
> ---
>  .../bindings/clock/ingenic,tcu-clocks.txt          | 42 ++++++++++++++++
>  .../bindings/interrupt-controller/ingenic,tcu.txt  | 39 +++++++++++++++
>  .../devicetree/bindings/mfd/ingenic,tcu.txt        | 56 ++++++++++++++++++++++
>  .../devicetree/bindings/timer/ingenic,tcu.txt      | 41 ++++++++++++++++
>  4 files changed, 178 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/clock/ingenic,tcu-clocks.txt
>  create mode 100644 Documentation/devicetree/bindings/interrupt-controller/ingenic,tcu.txt
>  create mode 100644 Documentation/devicetree/bindings/mfd/ingenic,tcu.txt
>  create mode 100644 Documentation/devicetree/bindings/timer/ingenic,tcu.txt
> 
>  v4: New patch in this series. Corresponds to V2 patches 3-4-5 with
>  added content.
> 
> diff --git a/Documentation/devicetree/bindings/clock/ingenic,tcu-clocks.txt b/Documentation/devicetree/bindings/clock/ingenic,tcu-clocks.txt
> new file mode 100644
> index 000000000000..471d27078599
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/clock/ingenic,tcu-clocks.txt
> @@ -0,0 +1,42 @@
> +Ingenic SoC TCU binding
> +
> +The TCU is the Timer/Counter Unit present in all Ingenic SoCs. It features 8
> +channels, each one having its own clock, that can be started and stopped,
> +reparented, and reclocked.
> +
> +Required properties:
> +- compatible : One of:
> +  * ingenic,jz4740-tcu-clocks,
> +  * ingenic,jz4770-tcu-clocks,
> +  * ingenic,jz4780-tcu-clocks.
> +- clocks : List of phandle & clock specifiers for clocks external to the TCU.
> +  The "pclk", "rtc" and "ext" clocks should be provided.
> +- clock-names : List of name strings for the external clocks.
> +- #clock-cells: Should be 1.
> +  Clock consumers specify this argument to identify a clock. The valid values
> +  may be found in <dt-bindings/clock/ingenic,tcu.h>.
> +
> +Example:

Let's just put one complete example in instead of all these duplicated 
and incomplete examples.

> +
> +/ {
> +	tcu: mfd@10002000 {
> +		compatible = "ingenic,tcu", "simple-mfd", "syscon";
> +		reg = <0x10002000 0x1000>;
> +		#address-cells = <1>;
> +		#size-cells = <1>;
> +		ranges = <0x0 0x10002000 0x1000>;
> +
> +		tcu_clk: clocks@10 {
> +			compatible = "ingenic,jz4740-tcu-clocks";
> +			reg = <0x10 0xff0>;
> +
> +			clocks = <&ext>, <&rtc>, <&pclk>;
> +			clock-names = "ext", "rtc", "pclk";
> +
> +			#clock-cells = <1>;
> +		};
> +	};
> +};
> +
> +For information about the top-level "ingenic,tcu" compatible node and other
> +children nodes, see Documentation/devicetree/bindings/mfd/ingenic,tcu.txt.
> diff --git a/Documentation/devicetree/bindings/interrupt-controller/ingenic,tcu.txt b/Documentation/devicetree/bindings/interrupt-controller/ingenic,tcu.txt
> new file mode 100644
> index 000000000000..7f3af2da77cd
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/interrupt-controller/ingenic,tcu.txt
> @@ -0,0 +1,39 @@
> +Ingenic SoCs Timer/Counter Unit Interrupt Controller
> +
> +Required properties:
> +
> +- compatible : should be "ingenic,<socname>-tcu-intc". Valid strings are:
> +  * ingenic,jz4740-tcu-intc
> +  * ingenic,jz4770-tcu-intc
> +  * ingenic,jz4780-tcu-intc
> +- interrupt-controller : Identifies the node as an interrupt controller
> +- #interrupt-cells : Specifies the number of cells needed to encode an
> +  interrupt source. The value shall be 1.
> +- interrupt-parent : phandle of the interrupt controller.
> +- interrupts : Specifies the interrupt the controller is connected to.
> +
> +Example:
> +
> +/ {
> +	tcu: mfd@10002000 {
> +		compatible = "ingenic,tcu", "simple-mfd", "syscon";
> +		reg = <0x10002000 0x1000>;
> +		#address-cells = <1>;
> +		#size-cells = <1>;
> +		ranges = <0x0 0x10002000 0x1000>;
> +
> +		tcu_irq: interrupt-controller@20 {
> +			compatible = "ingenic,jz4740-tcu-intc";
> +			reg = <0x20 0x20>;
> +
> +			interrupt-controller;
> +			#interrupt-cells = <1>;
> +
> +			interrupt-parent = <&intc>;
> +			interrupts = <15>;

The interrupt controller doesn't require any clocks?

> +		};
> +	};
> +};
> +
> +For information about the top-level "ingenic,tcu" compatible node and other
> +children nodes, see Documentation/devicetree/bindings/mfd/ingenic,tcu.txt.
> diff --git a/Documentation/devicetree/bindings/mfd/ingenic,tcu.txt b/Documentation/devicetree/bindings/mfd/ingenic,tcu.txt
> new file mode 100644
> index 000000000000..5742c3f21550
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/mfd/ingenic,tcu.txt
> @@ -0,0 +1,56 @@
> +Ingenic JZ47xx SoCs Timer/Counter Unit devicetree bindings
> +----------------------------------------------------------
> +
> +For a description of the TCU hardware and drivers, have a look at
> +Documentation/mips/ingenic-tcu.txt.
> +
> +The TCU is implemented as a parent node, whose role is to create the
> +regmap, and child nodes for the various drivers listed in the aforementioned
> +document.
> +
> +Required properties:
> +
> +- compatible: must be "ingenic,tcu", "simple-mfd", "syscon";
> +- reg: Should be the offset/length value corresponding to the TCU registers
> +- #address-cells: Should be <1>;
> +- #size-cells: Should be <1>;
> +- ranges: Should be one range for the full TCU registers area
> +
> +Accepted children nodes:
> +- Documentation/devicetree/bindings/interrupt-controller/ingenic,tcu.txt
> +- Documentation/devicetree/bindings/clock/ingenic,tcu-clocks.txt
> +- Documentation/devicetree/bindings/timer/ingenic,tcu.txt
> +
> +
> +Example:
> +
> +/ {
> +	tcu: mfd@10002000 {
> +		compatible = "ingenic,tcu", "simple-mfd", "syscon";
> +		reg = <0x10002000 0x1000>;
> +		#address-cells = <1>;
> +		#size-cells = <1>;
> +		ranges = <0x0 0x10002000 0x1000>;
> +
> +		tcu_irq: interrupt-controller@20 {
> +			compatible = "ingenic,jz4740-tcu-intc";
> +			reg = <0x20 0x20>;

I think you should drop this node and make the parent node the interrupt 
controller. That is the normal pattern where the parent node handles 
all the common functions. Otherwise, there is no need to have the parent 
node. You should then also drop simple-mfd as then you can control 
initialization order by initializing interrupt controller before 
its clients.

> +			...
> +		};
> +
> +		tcu_clk: clocks@10 {
> +			compatible = "ingenic,jz4740-tcu-clocks";
> +			reg = <0x10 0xff0>;
> +			...
> +		};
> +
> +		tcu_timer: timer@10 {
> +			compatible = "ingenic,jz4740-tcu";
> +			reg = <0x10 0xff0>;

Is this copy-n-paste or you really have 2 nodes at the same address? The 
latter is not valid.

> +			...
> +		};
> +	};
> +};
> +
> +For more information about the children node, refer to the documents listed
> +above in the "Accepted children nodes" section.
> diff --git a/Documentation/devicetree/bindings/timer/ingenic,tcu.txt b/Documentation/devicetree/bindings/timer/ingenic,tcu.txt
> new file mode 100644
> index 000000000000..f910b7e96783
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/timer/ingenic,tcu.txt
> @@ -0,0 +1,41 @@
> +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.
> +
> +Example:
> +
> +/ {
> +	tcu: mfd@10002000 {
> +		compatible = "ingenic,tcu", "simple-mfd", "syscon";
> +		reg = <0x10002000 0x1000>;
> +		#address-cells = <1>;
> +		#size-cells = <1>;
> +		ranges = <0x0 0x10002000 0x1000>;
> +
> +		tcu_timer: timer@10 {
> +			compatible = "ingenic,jz4740-tcu";
> +			reg = <0x10 0xff0>;
> +
> +			clocks = <&tcu_clk 0>, <&tcu_clk 1>, <&tcu_clk 2>, <&tcu_clk 3>,
> +					 <&tcu_clk 4>, <&tcu_clk 5>, <&tcu_clk 6>, <&tcu_clk 7>;
> +			clock-names = "timer0", "timer1", "timer2", "timer3",
> +						  "timer4", "timer5", "timer6", "timer7";
> +
> +			interrupt-parent = <&tcu_irq>;
> +			interrupts = <0 1 2 3 4 5 6 7>;

Thinking about this some more... You simply have 8 timers (and no other 
functions?) with some internal clock and irq controls for each timer. I 
don't think it really makes sense to create separate clock and irq 
drivers in that case. That would be like creating clock drivers for 
every clock divider in timers, pwms, uarts, etc. Unless the clocks get 
exposed to other parts of the system, then there is no point.

> +		};
> +	};
> +};
> +
> +For information about the top-level "ingenic,tcu" compatible node and other
> +children nodes, see Documentation/devicetree/bindings/mfd/ingenic,tcu.txt.
> -- 
> 2.11.0
>