Messages in this thread | | | Date | Mon, 7 Feb 2011 08:05:24 +0100 | From | Uwe Kleine-König <> | Subject | Re: [RFC,PATCH 1/3] Add a common struct clk |
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On Mon, Feb 07, 2011 at 02:07:57PM +0800, Jeremy Kerr wrote: > We currently have ~21 definitions of struct clk in the ARM architecture, > each defined on a per-platform basis. This makes it difficult to define > platform- (or architecture-) independent clock sources without making > assumptions about struct clk, and impossible to compile two > platforms with different struct clks into a single image. > > This change is an effort to unify struct clk where possible, by defining > a common struct clk, containing a set of clock operations. Different > clock implementations can set their own operations, and have a standard > interface for generic code. The callback interface is exposed to the > kernel proper, while the clock implementations only need to be seen by > the platform internals. > > This allows us to share clock code among platforms, and makes it > possible to dynamically create clock devices in platform-independent > code. > > Platforms can enable the generic struct clock through > CONFIG_USE_COMMON_STRUCT_CLK. In this case, the clock infrastructure > consists of a common struct clk: > > struct clk { > const struct clk_ops *ops; > unsigned int enable_count; > unsigned int prepare_count; > spinlock_t enable_lock; > struct mutex prepare_lock; > }; > > And a set of clock operations (defined per type of clock): > > struct clk_ops { > int (*enable)(struct clk *); > void (*disable)(struct clk *); > unsigned long (*get_rate)(struct clk *); > [...] > }; > > To define a hardware-specific clock, machine code can "subclass" the > struct clock into a new struct (adding any device-specific data), and > provide a set of operations: > > struct clk_foo { > struct clk clk; > void __iomem *some_register; > }; > > struct clk_ops clk_foo_ops = { > .get_rate = clk_foo_get_rate, > }; > > The common clock definitions are based on a development patch from Ben > Herrenschmidt <benh@kernel.crashing.org>. > > Signed-off-by: Jeremy Kerr <jeremy.kerr@canonical.com> > > --- > drivers/clk/Kconfig | 3 > drivers/clk/Makefile | 1 > drivers/clk/clk.c | 134 +++++++++++++++++++++++++++++++ > drivers/clk/clkdev.c | 5 + > include/linux/clk.h | 184 ++++++++++++++++++++++++++++++++++++++++--- > 5 files changed, 318 insertions(+), 9 deletions(-) > > diff --git a/drivers/clk/Kconfig b/drivers/clk/Kconfig > index 4168c88..6e3ae54 100644 > --- a/drivers/clk/Kconfig > +++ b/drivers/clk/Kconfig > @@ -2,3 +2,6 @@ > config CLKDEV_LOOKUP > bool > select HAVE_CLK > + > +config USE_COMMON_STRUCT_CLK > + bool > diff --git a/drivers/clk/Makefile b/drivers/clk/Makefile > index 07613fa..a1a06d3 100644 > --- a/drivers/clk/Makefile > +++ b/drivers/clk/Makefile > @@ -1,2 +1,3 @@ > > obj-$(CONFIG_CLKDEV_LOOKUP) += clkdev.o > +obj-$(CONFIG_USE_COMMON_STRUCT_CLK) += clk.o > diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c > new file mode 100644 > index 0000000..12e0daf > --- /dev/null > +++ b/drivers/clk/clk.c > @@ -0,0 +1,134 @@ > +/* > + * Copyright (C) 2010-2011 Canonical Ltd <jeremy.kerr@canonical.com> > + * > + * This program is free software; you can redistribute it and/or modify > + * it under the terms of the GNU General Public License version 2 as > + * published by the Free Software Foundation. > + * > + * Standard functionality for the common clock API. > + */ > + > +#include <linux/clk.h> > +#include <linux/module.h> > + > +int clk_prepare(struct clk *clk) > +{ > + int ret = 0; > + > + if (!clk->ops->prepare) > + return 0; > + > + mutex_lock(&clk->prepare_lock); > + if (clk->prepare_count == 0) > + ret = clk->ops->prepare(clk); > + > + if (!ret) > + clk->prepare_count++; > + mutex_unlock(&clk->prepare_lock); > + > + return 0; > +} > +EXPORT_SYMBOL_GPL(clk_prepare); > + > +void clk_unprepare(struct clk *clk) > +{ > + if (!clk->ops->unprepare) > + return; > + > + mutex_lock(&clk->prepare_lock); > + if (--clk->prepare_count == 0) > + clk->ops->unprepare(clk); > + > + mutex_unlock(&clk->prepare_lock); > +} > +EXPORT_SYMBOL_GPL(clk_unprepare); > + > +int clk_enable(struct clk *clk) > +{ > + int ret = 0; > + Did we want to check for prepare_count > 0 here? Russell's suggestion was to do that without holding any lock. (To make this a tad safer, you could use ACCESS_ONCE(clk->enable_count)++ below. (Suggested by paulmck on irc.))
Best regards Uwe
-- Pengutronix e.K. | Uwe Kleine-König | Industrial Linux Solutions | http://www.pengutronix.de/ | -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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