Re: [PATCH v5 4/5] clk/exynos5260: add macros and documentation for exynos5260

From: Tomasz Figa <t.figa@samsung.com>
To: Rahul Sharma <rahul.sharma@samsung.com>,
	linux-samsung-soc@vger.kernel.org, devicetree@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org
Cc: mturquette@linaro.org, kgene.kim@samsung.com,
	tomasz.figa@gmail.com, joshi@samsung.com, r.sh.open@gmail.com,
	pankaj.dubey@samsung.com
Subject: Re: [PATCH v5 4/5] clk/exynos5260: add macros and documentation for exynos5260
Date: Thu, 13 Mar 2014 13:36:28 +0100	[thread overview]
Message-ID: <5321A64C.3070902@samsung.com> (raw)
In-Reply-To: <1394636208-3125-5-git-send-email-rahul.sharma@samsung.com>

Hi Rahul,

On 12.03.2014 15:56, Rahul Sharma wrote:
> Add macros which are used as Clock IDs in DT and clock file.
> It also adds the documentation for the exynos5260 clocks.
>
> Signed-off-by: Rahul Sharma <Rahul.Sharma@samsung.com>
> ---
>   .../devicetree/bindings/clock/exynos5260-clock.txt |   55 +++++
>   include/dt-bindings/clock/exynos5260-clk.h         |  233 ++++++++++++++++++++
>   2 files changed, 288 insertions(+)
>   create mode 100644 Documentation/devicetree/bindings/clock/exynos5260-clock.txt
>   create mode 100644 include/dt-bindings/clock/exynos5260-clk.h
>
> diff --git a/Documentation/devicetree/bindings/clock/exynos5260-clock.txt b/Documentation/devicetree/bindings/clock/exynos5260-clock.txt
> new file mode 100644
> index 0000000..4128892
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/clock/exynos5260-clock.txt
> @@ -0,0 +1,55 @@
> +* Samsung Exynos5260 Clock Controller
> +
> +The Exynos5260 clock controller encapsulate all CMUs which are

s/encapsulate/encapsulates/

Anyway, I don't think there is any global clock controller entity that 
should be described here. The binding is related to several separate 
entities found on Exynos5260, i.e. particular CMUs.

> +instantiaited independently from the device-tree. As a whole, these

s/instantiaited/instantiated/
s/the device-tree/device tree/

> +CMUs generates and supplies clocks to various controllers within

s/generates/generate/
s/supplies/supply/

> +the Exynos5260 SoC.
> +
> +Required Properties:
> +
> +- compatible: should be one of the following.
> +	"exynos5260-clock-top"
> +	"exynos5260-clock-peri"
> +	"exynos5260-clock-egl"
> +	"exynos5260-clock-kfc"
> +	"exynos5260-clock-g2d"
> +	"exynos5260-clock-mif"
> +	"exynos5260-clock-mfc"
> +	"exynos5260-clock-g3d"
> +	"exynos5260-clock-fsys"
> +	"exynos5260-clock-aud"
> +	"exynos5260-clock-isp"
> +	"exynos5260-clock-gscl"
> +	"exynos5260-clock-disp"

Compatible strings should be prefixed with Samsung's vendor prefix, i.e. 
"samsung,".

> +
> +- reg: physical base address of the controller and length of memory mapped
> +  region.
> +
> +- #clock-cells: should be 1.

As implemented in patch [1] the clock core will be able to sort out 
dependencies between particular clock providers based on clock consumer 
bindings. This means that it would be a good idea to add clock 
properties to this binding and strictly specify which clocks outside 
particular CMU block are fed into the block.

So for example, if CMU TOP uses fin_pll clock, its node would need to 
have "clock-names" property with "fin_pll" entry and "clocks" property 
with respective entry pointing to the fixed rate clock node.

In general, all external, IO and PHY clocks fed into CMU blocks should 
be listed this way to have dependencies between clocks properly defined 
in the system.

[1] http://thread.gmane.org/gmane.linux.kernel/1654635

> +
> +The following is the list of clocks generated by each controller.

There is no list below. IMHO this sentence should be removed.

> Each
> +clock is assigned with a MACRO constant. These constants are defined in
> +"dt-bindings/clk/exynos5260-clk.h". DT client nodes use this MACRO to
> +specify the clock, which they want to consume.

IMHO the whole paragraph above can be rewritten taking 
samsung,s3c64xx-clock.txt as an example:

Each clock is assigned an identifier and client nodes can use this 
identifier to specify the clock which they consume. All available clocks 
are defined as preprocessor macros in dt-bindings/clock/exynos5260-clk.h 
header and can be used in device tree sources.

In addition to the above, a list of external clocks that need or may be 
present should be added. Again, see samsung,s3c64xx-clock.txt for an 
example.

> +
> +Example 1: An example of a clock controller node is listed below.
> +
> +	cmu_disp: clock-controller@0x14550000 {
> +		compatible = "exynos5260-clock-disp";

Incorrect compatible string.

> +		reg = <0x14550000 0x10000>;
> +		#clock-cells = <1>;
> +	};
> +
> +Example 2: UART controller node that consumes the clock generated by the
> +		peri clock controller. Refer to the standard clock bindings for
> +		information about 'clocks' and 'clock-names' property.
> +
> +	serial@12C00000 {
> +		compatible = "samsung,exynos4210-uart";
> +		reg = <0x12C00000 0x100>;
> +		interrupts = <0 146 0>;
> +		clocks = <&clock_peri PERI_PCLK_UART0>, <&clock_peri PERI_SCLK_UART0>;
> +		clock-names = "uart", "clk_uart_baud0";
> +		status = "disabled";
> +	};
> +
> diff --git a/include/dt-bindings/clock/exynos5260-clk.h b/include/dt-bindings/clock/exynos5260-clk.h
> new file mode 100644
> index 0000000..d6f4391
> --- /dev/null
> +++ b/include/dt-bindings/clock/exynos5260-clk.h
> @@ -0,0 +1,233 @@
> +/*
> + * Copyright (c) 2014 Samsung Electronics Co., Ltd.
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + *
> + * Provides Constants for Exynos5260 clocks.
> +*/
> +
> +#ifndef _DT_BINDINGS_CLK_EXYNOS5260_H
> +#define _DT_BINDINGS_CLK_EXYNOS5260_H
> +
> +/*
> + * Clock names:	XXXXX_YYYYYY_ZZZZ
> + *		|---| |----| |--|
> + *		 cmu   type   IP
> + */
> +
> +/* List Of Clocks For CMU_TOP */
> +#define FIN_PLL			1
> +#define TOP_FOUT_DISP_PLL	2
> +#define TOP_FOUT_AUD_PLL	3
> +#define TOP_SCLK_MMC0		4

[snip]

> +#define DISP_CLK_DSIM1		9
> +#define DISP_CLK_DPPHY		10
> +#define DISP_CLK_DP		11
> +#define DISP_SCLK_PIXEL		12
> +#define DISP_MOUT_HDMI_PHY_PIXEL_USER		13
> +#define DISP_MOUT_HDMI_PHY_PIXEL	14

nit: Incorrect alignment. Please indent further all the numbers to match 
the longest indentation level.

Best regards,
Tomasz