linux-kernel - RE: [PATCH v2 0/4] Add support for Exynos clock output configuration

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Date:	Wed, 25 Jun 2014 19:36:51 +0900
From:	Kukjin Kim <kgene.kim@...sung.com>
To:	'Tomasz Figa' <t.figa@...sung.com>,
	linux-samsung-soc@...r.kernel.org
Cc:	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	'Marek Szyprowski' <m.szyprowski@...sung.com>,
	'Mike Turquette' <mturquette@...aro.org>,
	'Rob Herring' <robh+dt@...nel.org>,
	'Mark Rutland' <mark.rutland@....com>,
	'Pankaj Dubey' <pankaj.dubey@...sung.com>,
	'Rahul Sharma' <rahul.sharma@...sung.com>,
	'Mark Brown' <broonie@...nel.org>,
	'Sylwester Nawrocki' <s.nawrocki@...sung.com>,
	'Daniel Drake' <drake@...lessm.com>,
	'Tomasz Figa' <tomasz.figa@...il.com>
Subject: RE: [PATCH v2 0/4] Add support for Exynos clock output configuration

Tomasz Figa wrote:
> 
Hi Tomasz,

> On all Exynos SoCs there is a dedicated CLKOUT pin that allows many of
> internal SoC clocks to be output from the SoC. The hardware structure

Yeah, because the CLKOUT pin is used for measure of the clock for debug on all
of exynos SoCs commonly.

> of CLKOUT related clocks looks as follows:
> 
> 	CMU	|---> clock0 --------->	|	PMU	|
> 		|			|		|
>     several	|---> clock1 ---------> |	mux	|
>     muxes	|			|	+	|---> CLKOUT
>     dividers	|       ...		|	gate	|
>     and gates	|			|		|
> 		|---> clockN ---------> |		|
> 
> Since the block responsible for handling the pin is PMU, not CMU,
> a separate driver, that binds to PMU node is required and acquires
> all input clocks by standard DT clock look-up. This way we don't need
> any cross-IP block drivers and cross-driver register sharing or
> nodes for fake devices.
> 
BTW, upcoming exynos5 SoCs have two muxs for CLKOUT and each mux is controlled
by CMU and PMU, so

The mux1 for CLKOUT in CMU is used to decide which clock in each sub-domain
will be out and the mux2 in PMU is used to decide which sub-domain will be out
via CLKOUT. So I want you to consider of all of exynos SoCs including upcoming
SoCs.

Thanks,
Kukjin

> To represent the PMU mux/gate clock, generic composite clock is registered.
> 
> Tested on Odroid U3, with HSIC/USB hub using CLKOUT as reference clock,
> with some additional patches.
> 
> Changes since v1:
> (http://www.spinics.net/lists/arm-kernel/msg333276.html)
>  - rebased onto next-20140624,
>  - fixed #clock-cells values in exynos5250.dtsi and exynos5420.dtsi,
>  - temporarily removed ISP CLKOUT clocks on Exynos4x12, until ISP clock
>    domain handling gets fixed in Exynos4 clock driver.
> Changes since RFC v1:
> (https://lkml.org/lkml/2014/5/15/506)
>  - rebased onto v5 of "Enable usbphy and hsotg for exynos4" series and
>    current HEAD of samsung-clk tree,
>  - added handling of suspend/resume in the driver,
>  - added missing CPU clocks on Exynos4,
>  - added CLK_SET_RATE_PARENT to CMU CLKOUT gates on Exynos4,
>  - fixed bit field width on Exynos4,
>  - added CLKOUT CMU registers of Exynos4 to save/restore list,
>  - added CLK_SET_RATE_PARENT and CLK_SET_RATE_NO_REPARENT to clkout clock,
>  - changed the binding to use 1-cell clock specifier to allow extension
>    with further PMU clocks in future, if needed.
> 
> Tomasz Figa (4):
>   clk: samsung: exynos4: Add missing CPU/DMC clock hierarchy
>   clk: samsung: exynos4: Add CLKOUT clock hierarchy
>   clk: samsung: Add driver to control CLKOUT line on Exynos SoCs
>   ARM: dts: exynos: Update PMU node with CLKOUT related data
> 
>  .../devicetree/bindings/arm/samsung/pmu.txt        |  30 ++++
>  arch/arm/boot/dts/exynos4210.dtsi                  |  10 ++
>  arch/arm/boot/dts/exynos4x12.dtsi                  |   7 +
>  arch/arm/boot/dts/exynos5250.dtsi                  |   3 +
>  arch/arm/boot/dts/exynos5420.dtsi                  |   3 +
>  drivers/clk/samsung/Makefile                       |   1 +
>  drivers/clk/samsung/clk-exynos-clkout.c            | 153 +++++++++++++++++++
>  drivers/clk/samsung/clk-exynos4.c                  | 166
++++++++++++++++++++-
>  include/dt-bindings/clock/exynos4.h                |   5 +
>  9 files changed, 374 insertions(+), 4 deletions(-)
>  create mode 100644 drivers/clk/samsung/clk-exynos-clkout.c
> 
> --
> 1.9.3

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