From 70aedd24d20e75198f5a0b11750faabbb56924e2 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Thu, 13 Aug 2009 12:17:48 +0200 Subject: genirq: Add buslock support Some interrupt chips are connected to a "slow" bus (i2c, spi ...). The bus access needs to sleep and therefor cannot be called in atomic contexts. Some of the generic interrupt management functions like disable_irq(), enable_irq() ... call interrupt chip functions with the irq_desc->lock held and interrupts disabled. This does not work for such devices. Provide a separate synchronization mechanism for such interrupt chips. The irq_chip structure is extended by two optional functions (bus_lock and bus_sync_and_unlock). The idea is to serialize the bus access for those operations in the core code so that drivers which are behind that bus operated interrupt controller do not have to worry about it and just can use the normal interfaces. To achieve this we add two function pointers to the irq_chip: bus_lock and bus_sync_unlock. bus_lock() is called to serialize access to the interrupt controller bus. Now the core code can issue chip->mask/unmask ... commands without changing the fast path code at all. The chip implementation merily stores that information in a chip private data structure and returns. No bus interaction as these functions are called from atomic context. After that bus_sync_unlock() is called outside the atomic context. Now the chip implementation issues the bus commands, waits for completion and unlocks the interrupt controller bus. The irq_chip implementation as pseudo code: struct irq_chip_data { struct mutex mutex; unsigned int irq_offset; unsigned long mask; unsigned long mask_status; } static void bus_lock(unsigned int irq) { struct irq_chip_data *data = get_irq_desc_chip_data(irq); mutex_lock(&data->mutex); } static void mask(unsigned int irq) { struct irq_chip_data *data = get_irq_desc_chip_data(irq); irq -= data->irq_offset; data->mask |= (1 << irq); } static void unmask(unsigned int irq) { struct irq_chip_data *data = get_irq_desc_chip_data(irq); irq -= data->irq_offset; data->mask &= ~(1 << irq); } static void bus_sync_unlock(unsigned int irq) { struct irq_chip_data *data = get_irq_desc_chip_data(irq); if (data->mask != data->mask_status) { do_bus_magic_to_set_mask(data->mask); data->mask_status = data->mask; } mutex_unlock(&data->mutex); } The device drivers can use request_threaded_irq, free_irq, disable_irq and enable_irq as usual with the only restriction that the calls need to come from non atomic context. Signed-off-by: Thomas Gleixner Cc: Mark Brown Cc: Dmitry Torokhov Cc: Trilok Soni Cc: Pavel Machek Cc: Brian Swetland Cc: Joonyoung Shim Cc: m.szyprowski@samsung.com Cc: t.fujak@samsung.com Cc: kyungmin.park@samsung.com, Cc: David Brownell Cc: Daniel Ribeiro Cc: arve@android.com Cc: Barry Song <21cnbao@gmail.com> --- include/linux/irq.h | 6 ++++++ 1 file changed, 6 insertions(+) (limited to 'include/linux') diff --git a/include/linux/irq.h b/include/linux/irq.h index 5e7c6ee8c35c..ce8171bc6fac 100644 --- a/include/linux/irq.h +++ b/include/linux/irq.h @@ -101,6 +101,9 @@ struct msi_desc; * @set_type: set the flow type (IRQ_TYPE_LEVEL/etc.) of an IRQ * @set_wake: enable/disable power-management wake-on of an IRQ * + * @bus_lock: function to lock access to slow bus (i2c) chips + * @bus_sync_unlock: function to sync and unlock slow bus (i2c) chips + * * @release: release function solely used by UML * @typename: obsoleted by name, kept as migration helper */ @@ -124,6 +127,9 @@ struct irq_chip { int (*set_type)(unsigned int irq, unsigned int flow_type); int (*set_wake)(unsigned int irq, unsigned int on); + void (*bus_lock)(unsigned int irq); + void (*bus_sync_unlock)(unsigned int irq); + /* Currently used only by UML, might disappear one day.*/ #ifdef CONFIG_IRQ_RELEASE_METHOD void (*release)(unsigned int irq, void *dev_id); -- cgit v1.2.3-59-g8ed1b