diff options
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/acpi/enumeration.txt | 2 | ||||
| -rw-r--r-- | Documentation/devicetree/bindings/gpio/renesas,gpio-rcar.txt | 6 | ||||
| -rw-r--r-- | Documentation/driver-model/devres.txt | 7 | ||||
| -rw-r--r-- | Documentation/gpio/driver.txt | 59 |
4 files changed, 73 insertions, 1 deletions
diff --git a/Documentation/acpi/enumeration.txt b/Documentation/acpi/enumeration.txt index 2a1519b87177..fd786ea13a1f 100644 --- a/Documentation/acpi/enumeration.txt +++ b/Documentation/acpi/enumeration.txt @@ -296,7 +296,7 @@ specifies the path to the controller. In order to use these GPIOs in Linux we need to translate them to the corresponding Linux GPIO descriptors. There is a standard GPIO API for that and is documented in -Documentation/gpio.txt. +Documentation/gpio/. In the above example we can get the corresponding two GPIO descriptors with a code like this: diff --git a/Documentation/devicetree/bindings/gpio/renesas,gpio-rcar.txt b/Documentation/devicetree/bindings/gpio/renesas,gpio-rcar.txt index f61cef74a212..941a26aa4322 100644 --- a/Documentation/devicetree/bindings/gpio/renesas,gpio-rcar.txt +++ b/Documentation/devicetree/bindings/gpio/renesas,gpio-rcar.txt @@ -21,6 +21,12 @@ Required Properties: GPIO_ACTIVE_HIGH and GPIO_ACTIVE_LOW flags are supported. - gpio-ranges: Range of pins managed by the GPIO controller. +Optional properties: + + - clocks: Must contain a reference to the functional clock. The property is + mandatory if the hardware implements a controllable functional clock for + the GPIO instance. + Please refer to gpio.txt in this directory for details of gpio-ranges property and the common GPIO bindings used by client devices. diff --git a/Documentation/driver-model/devres.txt b/Documentation/driver-model/devres.txt index 4f7897e99cba..10b8c5d2c797 100644 --- a/Documentation/driver-model/devres.txt +++ b/Documentation/driver-model/devres.txt @@ -308,3 +308,10 @@ SLAVE DMA ENGINE SPI devm_spi_register_master() + +GPIO + devm_gpiod_get() + devm_gpiod_get_index() + devm_gpiod_get_optional() + devm_gpiod_get_index_optional() + devm_gpiod_put() diff --git a/Documentation/gpio/driver.txt b/Documentation/gpio/driver.txt index f73cc7b5dc85..fa9a0a8b3734 100644 --- a/Documentation/gpio/driver.txt +++ b/Documentation/gpio/driver.txt @@ -73,6 +73,65 @@ The IRQ portions of the GPIO block are implemented using an irqchip, using the header <linux/irq.h>. So basically such a driver is utilizing two sub- systems simultaneously: gpio and irq. +GPIO irqchips usually fall in one of two categories: + +* CHAINED GPIO irqchips: these are usually the type that is embedded on + an SoC. This means that there is a fast IRQ handler for the GPIOs that + gets called in a chain from the parent IRQ handler, most typically the + system interrupt controller. This means the GPIO irqchip is registered + using irq_set_chained_handler() or the corresponding + gpiochip_set_chained_irqchip() helper function, and the GPIO irqchip + handler will be called immediately from the parent irqchip, while + holding the IRQs disabled. The GPIO irqchip will then end up calling + something like this sequence in its interrupt handler: + + static irqreturn_t tc3589x_gpio_irq(int irq, void *data) + chained_irq_enter(...); + generic_handle_irq(...); + chained_irq_exit(...); + + Chained GPIO irqchips typically can NOT set the .can_sleep flag on + struct gpio_chip, as everything happens directly in the callbacks. + +* NESTED THREADED GPIO irqchips: these are off-chip GPIO expanders and any + other GPIO irqchip residing on the other side of a sleeping bus. Of course + such drivers that need slow bus traffic to read out IRQ status and similar, + traffic which may in turn incur other IRQs to happen, cannot be handled + in a quick IRQ handler with IRQs disabled. Instead they need to spawn a + thread and then mask the parent IRQ line until the interrupt is handled + by the driver. The hallmark of this driver is to call something like + this in its interrupt handler: + + static irqreturn_t tc3589x_gpio_irq(int irq, void *data) + ... + handle_nested_irq(irq); + + The hallmark of threaded GPIO irqchips is that they set the .can_sleep + flag on struct gpio_chip to true, indicating that this chip may sleep + when accessing the GPIOs. + +To help out in handling the set-up and management of GPIO irqchips and the +associated irqdomain and resource allocation callbacks, the gpiolib has +some helpers that can be enabled by selecting the GPIOLIB_IRQCHIP Kconfig +symbol: + +* gpiochip_irqchip_add(): adds an irqchip to a gpiochip. It will pass + the struct gpio_chip* for the chip to all IRQ callbacks, so the callbacks + need to embed the gpio_chip in its state container and obtain a pointer + to the container using container_of(). + (See Documentation/driver-model/design-patterns.txt) + +* gpiochip_set_chained_irqchip(): sets up a chained irq handler for a + gpio_chip from a parent IRQ and passes the struct gpio_chip* as handler + data. (Notice handler data, since the irqchip data is likely used by the + parent irqchip!) This is for the chained type of chip. + +To use the helpers please keep the following in mind: + +- Make sure to assign all relevant members of the struct gpio_chip so that + the irqchip can initialize. E.g. .dev and .can_sleep shall be set up + properly. + It is legal for any IRQ consumer to request an IRQ from any irqchip no matter if that is a combined GPIO+IRQ driver. The basic premise is that gpio_chip and irq_chip are orthogonal, and offering their services independent of each |