ARM: omap: clk: add clk_prepare and clk_unprepare

As part of Common Clk Framework (CCF) the clk_enable() operation
was split into a clk_prepare() which could sleep, and a clk_enable()
which should never sleep. Similarly the clk_disable() was
split into clk_disable() and clk_unprepare(). This was
needed to handle complex cases where in a clk gate/ungate
would require a slow and a fast part to be implemented.
None of the clocks below seem to be in the 'complex' clocks
category and are just simple clocks which are enabled/disabled
through simple register writes.
Most of the instances also seem to be called in non-atomic
context which means its safe to move all of those from
using a clk_enable() to clk_prepare_enable() and clk_disable() to
clk_disable_unprepare().

For some others, mainly the ones handled through the hwmod framework
there is a possibility that they get called in either an atomic
or a non-atomic context.

The way these get handled below work only as long as clk_prepare
is implemented as a no-op (which is the case today) since this gets
called very early at boot while most subsystems are unavailable.
Hence these are marked with a *HACK* comment, which says we need
to re-visit these once we start doing something meaningful with
clk_prepare/clk_unprepare like doing voltage scaling or something
that involves i2c.

This is in preparation of OMAP moving to CCF.

Based on initial changes from Mike Turquette.

Signed-off-by: Rajendra Nayak <rnayak@ti.com>
Signed-off-by: Paul Walmsley <paul@pwsan.com>

1 files changed, 27 insertions, 0 deletions

diff --git a/arch/arm/mach-omap2/omap_hwmod.c b/arch/arm/mach-omap2/omap_hwmod.c
index 6504f0e8d96e..99fd3bb3c432 100644
--- a/arch/arm/mach-omap2/omap_hwmod.c
+++ b/arch/arm/mach-omap2/omap_hwmod.c
@@ -685,6 +685,15 @@ static int _init_main_clk(struct omap_hwmod *oh)
 			   oh->name, oh->main_clk);
 		return -EINVAL;
 	}
+	/*
+	 * HACK: This needs a re-visit once clk_prepare() is implemented
+	 * to do something meaningful. Today its just a no-op.
+	 * If clk_prepare() is used at some point to do things like
+	 * voltage scaling etc, then this would have to be moved to
+	 * some point where subsystems like i2c and pmic become
+	 * available.
+	 */
+	clk_prepare(oh->_clk);
 
 	if (!oh->_clk->clkdm)
 		pr_warning("omap_hwmod: %s: missing clockdomain for %s.\n",
@@ -722,6 +731,15 @@ static int _init_interface_clks(struct omap_hwmod *oh)
 			ret = -EINVAL;
 		}
 		os->_clk = c;
+		/*
+		 * HACK: This needs a re-visit once clk_prepare() is implemented
+		 * to do something meaningful. Today its just a no-op.
+		 * If clk_prepare() is used at some point to do things like
+		 * voltage scaling etc, then this would have to be moved to
+		 * some point where subsystems like i2c and pmic become
+		 * available.
+		 */
+		clk_prepare(os->_clk);
 	}
 
 	return ret;
@@ -749,6 +767,15 @@ static int _init_opt_clks(struct omap_hwmod *oh)
 			ret = -EINVAL;
 		}
 		oc->_clk = c;
+		/*
+		 * HACK: This needs a re-visit once clk_prepare() is implemented
+		 * to do something meaningful. Today its just a no-op.
+		 * If clk_prepare() is used at some point to do things like
+		 * voltage scaling etc, then this would have to be moved to
+		 * some point where subsystems like i2c and pmic become
+		 * available.
+		 */
+		clk_prepare(oc->_clk);
 	}
 
 	return ret;