Hello, This series allows core code and driver code to register for notification when a clock's rate or parent changes. This is currently used by driver code that must be notified whenever power management code (e.g., CPUFreq) causes system rate changes that affect the driver's clock. There are three notifier messages: 1. a pre-change notifier, called before the change; 2. a post-change notifier, called after the change; and 3. an abort notifier, called if the change fails for any reason after the pre-change notifier callbacks have run. Since the implementation uses a blocking notifier, notifier code may block waiting for devices to quiesce; but long delays here will reduce the effectiveness of DVFS. Since notifier callbacks are called with clocks_mutex held, callback code must not re-enter the clock framework. Pre-change notifiers are passed the current clock rate and the desired clock rate, so drivers can adjust any internal dividers appropriately. (To minimize performance and memory usage impact, post-change notifiers are passed only the desired clock rate, i.e., the clock rate after the rate change.) The notifiers are called even if the clock rate is the same before and after the change. This is because reprogramming a clock's parent or rate may briefly disrupt the clock. The interface to the notifiers is via: int clk_notifier_register(struct clk *clk, struct notifier_block *nb); int clk_notifier_unregister(struct clk *clk, struct notifier_block *nb); Until prototypes for these functions are made available in include/linux/clk.h, drivers should pass function pointers to clk_notifier_register() and clk_notifier_unregister() via their platform_data struct. This series is a collaboration between Tero Kristo <tero.kristo@xxxxxxxxx> and Paul Walmsley <paul@xxxxxxxxx> and several others. Hiroshi Doyu <Hiroshi.DOYU@xxxxxxxxx> tracked down and fixed a bug where blocking_notifier_chain_*() were called while interrupts were disabled. Nishanth Menon <nm@xxxxxx> found and fixed a bug in the clk_notifier_unregister() path, where a list_del() was missing. And thanks to Jouni Högander <jouni.hogander@xxxxxxxxx> for comments and review during the evolution of these patches. Registration and callbacks on rate change and parent change tested on BeagleBoard (OMAP3530 ES2.1). Comments welcomed. --- text data bss dec hex filename 3439981 175136 111800 3726917 38de45 vmlinux.beagle.orig 3441545 176000 111800 3729345 38e7c1 vmlinux.beagle arch/arm/mach-omap2/clock.c | 30 ++++ arch/arm/mach-omap2/clock.h | 1 arch/arm/mach-omap2/clock24xx.c | 1 arch/arm/mach-omap2/clock34xx.c | 1 arch/arm/plat-omap/clock.c | 256 +++++++++++++++++++++++++++++++ arch/arm/plat-omap/include/mach/clock.h | 68 ++++++++ 6 files changed, 357 insertions(+), 0 deletions(-) -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
