[PATCH RFC v3 0/2] clk: Support for DT assigned clock parents and rates

Sylwester Nawrocki
2014-03-27T12:16:17Z

This patch set adds a DT binding documentation for new 'clock-parents'
and 'clock-rates' DT properties and a helper function to parse them.
The helper is now being called from within the driver core, similarly
as it is done for the pins configuration binding to a device.

Patch 1/2 adds a variant of of_clk_get() function which accepts name of
a DT property containing list of phandle + clock specifier pairs, as
opposed to hard coded "clocks" property name in of_clk_get().
As Mike suggested I've renamed this function to of_clk_get_by_property().

Patch 2/2 actually adds the code searching for related DT properties at
device node and performing re-parenting and/or clock frequency setting
as specified.

I didn't add sorting of clocks depending on parentship relation when
setting the clock rates, it could be added in next iteration if it's
decided it's required.

Changes since v2:
- code reordering to ensure there is no build errors, the clock
configuration code moved to a separate file,
- introduced an 'assigned-clocks' DT node which is supposed to contain
clocks, clock-parents, clock-rates properties and be child node
a clock provider node, and a code parsing it called from of_clk_init();
It's for clocks which are not directly connected to consumer devices.
An alternative would be to list such assigned clocks in 'clocks'
property, along with "proper" parent clocks, but then there would
be phandles in clocks property of a node pointing to itself and it
would require proper handling in of_clock_init().
I actually tried it but it looked a bit ugly and chose this time to
use an extra subnode.

Changes since v1:
- updated DT binding documentation,
- dropped the platform bus notifier, the clock setup routine is now
being called directly from the driver core before a driver probe() call;
this has an advantage such as all bus types are handled and any errors
are propagated, so that, for instance a driver probe() can be deferred
also when resources specified by clock-parents/clock-rates properties
are not yet available; an alternative would be to let drivers call
of_clk_device_setup() directly,
- dropped the patch adding a macro definition for maximum DT property
name length for now.

Open issues:
- handling of errors from of_clk_get_by_property() could be improved,
currently ENOENT is returned by this function not only for a null
entry.

This series has been tested on ARM, on Exynos4412 Trats2 board, with
patch [1] applied. RFC v2 can be found at [2].

[1] https://lkml.org/lkml/2014/3/27/97
[2] https://lkml.org/lkml/2014/3/3/324

Sylwester Nawrocki (2):
clk: Add function parsing arbitrary clock list DT property
clk: Add handling of clk parent and rate assigned from DT

.../devicetree/bindings/clock/clock-bindings.txt | 26 ++++++
drivers/base/dd.c | 7 ++
drivers/clk/Makefile | 1 +
drivers/clk/clk-conf.c | 87 ++++++++++++++++++++
drivers/clk/clk.c | 10 ++-
drivers/clk/clkdev.c | 25 +++++-
include/linux/clk.h | 7 ++
include/linux/clk/clk-conf.h | 19 +++++
8 files changed, 177 insertions(+), 5 deletions(-)
create mode 100644 drivers/clk/clk-conf.c
create mode 100644 include/linux/clk/clk-conf.h

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1.7.9.5