Re: [RFC 6/8] of: add clock providers
From: Shawn Guo <hidden>
Date: 2011-11-21 15:25:17
Also in:
linux-arm-kernel, lkml
On Tue, Nov 08, 2011 at 06:19:41PM -0700, Grant Likely wrote:
quoted hunk ↗ jump to hunk
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-s3s/WqlpOiPyB63q8FvJNQ@public.gmane.org> --- .../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.hdiff --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); +}