linux-kernel - Re: [RESEND PATCH 1/1] clk: add DT support for clock gating control

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Message-ID: <4FFFED7C.9050406@googlemail.com>
Date:	Fri, 13 Jul 2012 11:42:20 +0200
From:	Sebastian Hesselbarh <sebastian.hesselbarth@...glemail.com>
To:	Rob Herring <robherring2@...il.com>
CC:	Grant Likely <grant.likely@...retlab.ca>,
	Rob Landley <rob@...dley.net>,
	Mike Turquette <mturquette@...com>,
	devicetree-discuss@...ts.ozlabs.org, linux-doc@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [RESEND PATCH 1/1] clk: add DT support for clock gating control

On 07/13/2012 05:19 AM, Rob Herring wrote:
> What's implemented in Linux should not define the binding. The binding
> should describe the hardware.
> [...]
> True, but not your problem to implement. A binding doesn't necessarily
> mean there is a full Linux implementation. We just don't want to create
> something only to find others need something completely different.

Ok, what about a DT describing the following for a simple register-based
clock gating controller and the corresponding gated-clock independent of
the controller. I am sure there are a bunch of SoCs out there that
control their clock gates by writing some bits to a register. If that
DT description matches your expectations, I ll prepare patches with
documentation and implementation for common clock framework.

Sebastian

--
  /* Simple clock gating controller based on bitmasks and register */
cgc: clock-gating-control@...00000 {
   compatible = "clock-gating-control-register";
   reg = <0xf1000000 0x4>;

   /* Clock gating control with one bit at bit position 0
      enable with (1<<0), disable with (0<<0) */
   cgctrl_usb0: cgc_usb0 {
     clock-gating-control,shift = <0>;
     clock-gating-control,mask = <1>;
     clock-gating-control,enable = <1>;
     clock-gating-control,disable = <0>;
   };

   /* Clock gating control with two bits at bit position 1-2
      enable with (2<<1), disable with (0<<1) */
   cgctrl_sata: cgc_sata {
     clock-gating-control,shift = <1>;
     clock-gating-control,mask = <3>;
     clock-gating-control,enable = <2>;
     clock-gating-control,disable = <0>;
   };
};

/* Generic clock gate description that can be used with
    any clock gating controller */
cg_usb0: clockgate@0 {
   compatible = "gated-clock";
   #clock-cells = <0>;
   clocks = <&osc>;
   clock-gate-control = <&cgctrl_usb0>;
};
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