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Message-ID: <20111121153716.GA16417@S2100-06.ap.freescale.net>
Date: Mon, 21 Nov 2011 23:37:18 +0800
From: Shawn Guo <shawn.guo@...escale.com>
To: Grant Likely <grant.likely@...retlab.ca>
CC: <devicetree-discuss@...ts.ozlabs.org>,
<linux-arm-kernel@...ts.infradead.org>,
Sascha Hauer <kernel@...gutronix.de>,
Rob Herring <rob.herring@...xeda.com>,
<linux-kernel@...r.kernel.org>
Subject: Re: [RFC 6/8] of: add clock providers
On Tue, Nov 08, 2011 at 06:19:41PM -0700, Grant Likely wrote:
> Based on work by Ben Herrenschmidt and Jeremy Kerr, this patch adds an
> of_clk_get function to allow platforms to retrieve clock data from the
> device tree.
>
> Platform register a provider through of_clk_add_provider, which will be
> called when a device references the provider's OF node for a clock
> reference.
>
> Signed-off-by: Grant Likely <grant.likely@...retlab.ca>
> ---
> .../devicetree/bindings/clock/clock-bindings.txt | 109 +++++++++++++++++
> drivers/of/Kconfig | 6 +
> drivers/of/Makefile | 1 +
> drivers/of/clock.c | 129 ++++++++++++++++++++
> include/linux/of_clk.h | 37 ++++++
> 5 files changed, 282 insertions(+), 0 deletions(-)
> create mode 100644 Documentation/devicetree/bindings/clock/clock-bindings.txt
> create mode 100644 drivers/of/clock.c
> create mode 100644 include/linux/of_clk.h
>
> diff --git a/Documentation/devicetree/bindings/clock/clock-bindings.txt b/Documentation/devicetree/bindings/clock/clock-bindings.txt
> new file mode 100644
> index 0000000..4770c7e
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/clock/clock-bindings.txt
> @@ -0,0 +1,109 @@
> +This binding is a work-in-progress, and are based on some experimental
> +work by benh[1].
> +
> +Sources of clock signal can be represented by any node in the device
> +tree. Those nodes are designated as clock providers. Clock consumer
> +nodes use a phandle and clock specifier pair to connect clock provider
> +outputs to clock inputs. Similar to the gpio specifiers, a clock
> +specifier is an array of one more more cells identifying the clock
> +output on a device. The length of a clock specifier is defined by the
> +value of a #clock-cells property in the clock provider node.
> +
> +[1] http://patchwork.ozlabs.org/patch/31551/
> +
> +==Clock providers==
> +
> +Required properties:
> +#clock-cells: Number of cells in a clock specifier; typically will be
> + set to 1
> +
> +Optional properties:
> +clock-output-name: Recommended to be a list of strings of clock output signal
> + names indexed by the first cell in the clock specifier.
> + However, the meaning of clock-output-names is domain
s/clock-output-names/clock-output-name?
> + specific to the clock provider, and is only provided to
> + encourage using the same meaning for the majority of clock
> + providers. This format may not work for clock providers
> + using a complex clock specifier format. In those cases it
> + is recommended to omit this property and create a binding
> + specific names property.
> +
> + Clock consumer nodes must never directly reference
> + the provider's clock-output-names property.
s/clock-output-names/clock-output-name?
> +
> +For example:
> +
> + oscillator {
> + #clock-cells = <1>;
> + clock-output-name = "ckil", "ckih";
> + };
> +
> +- this node defines a device with two clock outputs, the first named
> + "ckil" and the second named "ckih". Consumer nodes always reference
> + clocks by index. The names should reflect the clock output signal
> + names for the device.
> +
> +==Clock consumers==
> +
> +Required properties:
> +clock-input: List of phandle and clock specifier pairs, one pair
> + for each clock input to the device.
> +clock-input-name: List of clock input name strings sorted in the same
> + order as the clock-input property. Consumers drivers
> + will use clock-input-name to match clock input names
> + with clock-input specifiers.
> +
> +For example:
> +
> + uart {
> + clock-input = <&osc 1> <&ref 0>;
^
Comma is missed?
> + clock-input-name = "baud", "register";
> + };
[...]
> +struct clk *of_clk_get(struct device_node *np, int index)
> +{
> + struct of_phandle_args clkspec;
> + struct clk *clk;
> + int rc;
> +
> + if (index < 0)
> + return NULL;
> +
> + rc = of_parse_phandle_with_args(np, "clock", "#clock-cells", index,
According to binding document above, s/clock/clock-input?
> + &clkspec);
> + if (rc)
> + return NULL;
> +
> + clk = __of_clk_get_from_provider(&clkspec);
> + of_node_put(clkspec.np);
> + return clk;
> +}
> +
> +struct clk *of_clk_get_by_name(struct device_node *np, const char *name)
> +{
> + int index = 0;
> +
> + if (name)
> + index = of_property_match_string(np, "clock-input-names", name);
If it fails to match name, we may want to force 'index' back to 0.
Also according to binding document above,
s/clock-input-names/clock-input-name? Hope you do not want to
change binding document to get them aligned. I have written code
per binding document :)
Regards,
Shawn
> + return of_clk_get(np, index);
> +}
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