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From: Jeremy Kerr on 11 Jul 2010 22:40
These patches are an attempt to allow platforms to share clock code. At
present, the definitions of 'struct clk' are local to platform code,
which makes allocating and initialising cross-platform clock sources
difficult, and makes it impossible to compile a single image containing
support for two ARM platforms with different struct clks.
The two patches are for the architecture-independent kernel code,
introducing the common clk infrastructure. The changelog for the first
patch includes details about the new clock definitions.
As requested by rmk, I've put together a small series of patches
illustrating the usage of the common struct clock on the ARM imx51
platform. These are available in my git tree:
in the clk-common-mx51 branch (clk-common..clk-common-mx51). There is
also a port for versatile (clk-common-versatile) in this tree too.
The approach I've taken with the imx51 port is to temporarly duplicate
the platform-common clock code (ie, for all mxc-based boards) to enable
usage of the common struct clk on one machine (imx51), while leaving the
others as-is. For a proper platform-wide usage of the common struct clk,
we'd be better off doing the whole platform at once. However, mx51 is
the only mxc-based HW I have, hence the duplicated example port.
In the example port, the first change simply converts the mxc's struct
clk to a struct clk_mxc, using the new API. The subsequent patches move
certain clocks to more specific data structures (eg clk_fixed and
clk_pll) where possible.
Ben Herrenschmidt is looking at using common struct clk code for powerpc
too, hence the kernel-wide approach.
Many thanks to the following for their input:
* Ben Dooks <ben-linux(a)fluff.org>
* Baruch Siach <baruch(a)tkos.co.il>
* Russell King <linux(a)arm.linux.org.uk>
* Uwe Kleine-König <u.kleine-koenig(a)pengutronix.de>
* Lorenzo Pieralisi <Lorenzo.Pieralisi(a)arm.com>
rmk - now that we've had a few platforms ported to the common clk
infrastructure, I believe it's ready to merge. If so, do you want this
in the patch tracker? Otherwise, let me know what needs changing.
* fixed up references to 'clk_operations' in the changelog
* uninline main API, and share definitions with !USE_COMMON_STRUCT_CLK
* add __clk_get
* delay mutex init
* kerneldoc for struct clk
* use mutex for enable/disable locking
* DEFINE_CLK -> INIT_CLK, and pass the clk name for mutex init
* struct clk_operations -> struct clk_ops
* do clock usage refcounting in common code
* provide sample port
* no longer ARM-specific
* use clk_operations
Jeremy Kerr (2):
Add a common struct clk
clk: Generic support for fixed-rate clocks
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