clock updates for the QUP driver from Linux 3.4 and CAF msm-3.4
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msm: clock: Support clk_prepare/unprepare()

Fill in the boiler plate prepare()/unprepare() code. Add a
prepare count and a prepare lock to protect the prepare/unprepare
paths. Also handle the parent/child relationship similarly to how
enable/disable is done.

In particular, WARN() whenever a driver calls clk_enable() before
calling clk_prepare() and whenever a driver calls clk_unprepare()
before calling clk_disable(). This should catch a few bugs even
though it's technically not SMP safe if an enable call is racing
with an unprepare call for example.

We also mark PLLs and XOs as already warned since those are
mostly internal clocks that driver authors aren't aware of. The
markings will be removed when the local clock driver is updated
to handle prepare/unprepare in another patch.

Change-Id: I41dd39d27a279f3477c6e1cef292ac5308d65243
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
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msm: clock: Migrate to prepare()/unprepare() APIs

Replace calls to clk_enable()/clk_disable() with calls to
clk_prepare_enable()/clk_unprepare_disable(). This is safe to do
because all these calls are made from non-atomic context.

Change-Id: I8bbb2c5df9a23796b808d4f882ffdb04319477ea
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
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clk: add config option HAVE_CLK_PREPARE into Kconfig
The commit 40d3e0f (clk: provide prepare/unprepare functions) provides
the config option HAVE_CLK_PREPARE for platforms that have
prepare/unprepare implementation to select.  This patch adds the option
into drivers/clk/Kconfig, so that it can be actually selected.

Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
Cc: Russell King <rmk+kernel@arm.linux.org.uk>
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clk: add helper functions clk_prepare_enable and clk_disable_unprepare
It's for migrating to generic clk framework API.

The helper functions  help cases clk_enable/clk_disable is used
in non-atomic context.
For example, Call clk_enable in probe and clk_disable in remove.

Signed-off-by: Richard Zhao <richard.zhao@linaro.org>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
Cc: Russell King <linux@arm.linux.org.uk>
Acked-by: Marek Vasut <marek.vasut@gmail.com>