diff options
Diffstat (limited to 'Documentation/driver-api/gpio/driver.rst')
| -rw-r--r-- | Documentation/driver-api/gpio/driver.rst | 272 |
1 files changed, 200 insertions, 72 deletions
diff --git a/Documentation/driver-api/gpio/driver.rst b/Documentation/driver-api/gpio/driver.rst index 2ff743105927..bf6319cc531b 100644 --- a/Documentation/driver-api/gpio/driver.rst +++ b/Documentation/driver-api/gpio/driver.rst @@ -119,7 +119,7 @@ GPIO lines with debounce support Debouncing is a configuration set to a pin indicating that it is connected to a mechanical switch or button, or similar that may bounce. Bouncing means the line is pulled high/low quickly at very short intervals for mechanical -reasons. This can result in the value being unstable or irqs fireing repeatedly +reasons. This can result in the value being unstable or irqs firing repeatedly unless the line is debounced. Debouncing in practice involves setting up a timer when something happens on @@ -218,10 +218,10 @@ not support open drain/open source in hardware, the GPIO library will instead use a trick: when a line is set as output, if the line is flagged as open drain, and the IN output value is low, it will be driven low as usual. But if the IN output value is set to high, it will instead *NOT* be driven high, -instead it will be switched to input, as input mode is high impedance, thus -achieveing an "open drain emulation" of sorts: electrically the behaviour will -be identical, with the exception of possible hardware glitches when switching -the mode of the line. +instead it will be switched to input, as input mode is an equivalent to +high impedance, thus achieving an "open drain emulation" of sorts: electrically +the behaviour will be identical, with the exception of possible hardware glitches +when switching the mode of the line. For open source configuration the same principle is used, just that instead of actively driving the line low, it is set to input. @@ -342,12 +342,12 @@ Cascaded GPIO irqchips usually fall in one of three categories: forced to a thread. The "fake?" raw lock can be used to work around this problem:: - raw_spinlock_t wa_lock; - static irqreturn_t omap_gpio_irq_handler(int irq, void *gpiobank) - unsigned long wa_lock_flags; - raw_spin_lock_irqsave(&bank->wa_lock, wa_lock_flags); - generic_handle_irq(irq_find_mapping(bank->chip.irq.domain, bit)); - raw_spin_unlock_irqrestore(&bank->wa_lock, wa_lock_flags); + raw_spinlock_t wa_lock; + static irqreturn_t omap_gpio_irq_handler(int irq, void *gpiobank) + unsigned long wa_lock_flags; + raw_spin_lock_irqsave(&bank->wa_lock, wa_lock_flags); + generic_handle_irq(irq_find_mapping(bank->chip.irq.domain, bit)); + raw_spin_unlock_irqrestore(&bank->wa_lock, wa_lock_flags); - GENERIC CHAINED GPIO IRQCHIPS: these are the same as "CHAINED GPIO irqchips", but chained IRQ handlers are not used. Instead GPIO IRQs dispatching is @@ -416,30 +416,69 @@ The preferred way to set up the helpers is to fill in the struct gpio_irq_chip inside struct gpio_chip before adding the gpio_chip. If you do this, the additional irq_chip will be set up by gpiolib at the same time as setting up the rest of the GPIO functionality. The following -is a typical example of a cascaded interrupt handler using gpio_irq_chip:: +is a typical example of a chained cascaded interrupt handler using +the gpio_irq_chip. Note how the mask/unmask (or disable/enable) functions +call into the core gpiolib code: .. code-block:: c - /* Typical state container with dynamic irqchip */ + /* Typical state container */ struct my_gpio { struct gpio_chip gc; - struct irq_chip irq; + }; + + static void my_gpio_mask_irq(struct irq_data *d) + { + struct gpio_chip *gc = irq_data_get_irq_chip_data(d); + irq_hw_number_t hwirq = irqd_to_hwirq(d); + + /* + * Perform any necessary action to mask the interrupt, + * and then call into the core code to synchronise the + * state. + */ + + gpiochip_disable_irq(gc, hwirq); + } + + static void my_gpio_unmask_irq(struct irq_data *d) + { + struct gpio_chip *gc = irq_data_get_irq_chip_data(d); + irq_hw_number_t hwirq = irqd_to_hwirq(d); + + gpiochip_enable_irq(gc, hwirq); + + /* + * Perform any necessary action to unmask the interrupt, + * after having called into the core code to synchronise + * the state. + */ + } + + /* + * Statically populate the irqchip. Note that it is made const + * (further indicated by the IRQCHIP_IMMUTABLE flag), and that + * the GPIOCHIP_IRQ_RESOURCE_HELPER macro adds some extra + * callbacks to the structure. + */ + static const struct irq_chip my_gpio_irq_chip = { + .name = "my_gpio_irq", + .irq_ack = my_gpio_ack_irq, + .irq_mask = my_gpio_mask_irq, + .irq_unmask = my_gpio_unmask_irq, + .irq_set_type = my_gpio_set_irq_type, + .flags = IRQCHIP_IMMUTABLE, + /* Provide the gpio resource callbacks */ + GPIOCHIP_IRQ_RESOURCE_HELPERS, }; int irq; /* from platform etc */ struct my_gpio *g; struct gpio_irq_chip *girq; - /* Set up the irqchip dynamically */ - g->irq.name = "my_gpio_irq"; - g->irq.irq_ack = my_gpio_ack_irq; - g->irq.irq_mask = my_gpio_mask_irq; - g->irq.irq_unmask = my_gpio_unmask_irq; - g->irq.irq_set_type = my_gpio_set_irq_type; - /* Get a pointer to the gpio_irq_chip */ girq = &g->gc.irq; - girq->chip = &g->irq; + gpio_irq_chip_set_chip(girq, &my_gpio_irq_chip); girq->parent_handler = ftgpio_gpio_irq_handler; girq->num_parents = 1; girq->parents = devm_kcalloc(dev, 1, sizeof(*girq->parents), @@ -452,32 +491,147 @@ is a typical example of a cascaded interrupt handler using gpio_irq_chip:: return devm_gpiochip_add_data(dev, &g->gc, g); -The helper support using hierarchical interrupt controllers as well. -In this case the typical set-up will look like this:: +The helper supports using threaded interrupts as well. Then you just request +the interrupt separately and go with it: .. code-block:: c - /* Typical state container with dynamic irqchip */ + /* Typical state container */ struct my_gpio { struct gpio_chip gc; - struct irq_chip irq; - struct fwnode_handle *fwnode; + }; + + static void my_gpio_mask_irq(struct irq_data *d) + { + struct gpio_chip *gc = irq_data_get_irq_chip_data(d); + irq_hw_number_t hwirq = irqd_to_hwirq(d); + + /* + * Perform any necessary action to mask the interrupt, + * and then call into the core code to synchronise the + * state. + */ + + gpiochip_disable_irq(gc, hwirq); + } + + static void my_gpio_unmask_irq(struct irq_data *d) + { + struct gpio_chip *gc = irq_data_get_irq_chip_data(d); + irq_hw_number_t hwirq = irqd_to_hwirq(d); + + gpiochip_enable_irq(gc, hwirq); + + /* + * Perform any necessary action to unmask the interrupt, + * after having called into the core code to synchronise + * the state. + */ + } + + /* + * Statically populate the irqchip. Note that it is made const + * (further indicated by the IRQCHIP_IMMUTABLE flag), and that + * the GPIOCHIP_IRQ_RESOURCE_HELPER macro adds some extra + * callbacks to the structure. + */ + static const struct irq_chip my_gpio_irq_chip = { + .name = "my_gpio_irq", + .irq_ack = my_gpio_ack_irq, + .irq_mask = my_gpio_mask_irq, + .irq_unmask = my_gpio_unmask_irq, + .irq_set_type = my_gpio_set_irq_type, + .flags = IRQCHIP_IMMUTABLE, + /* Provide the gpio resource callbacks */ + GPIOCHIP_IRQ_RESOURCE_HELPERS, }; int irq; /* from platform etc */ struct my_gpio *g; struct gpio_irq_chip *girq; - /* Set up the irqchip dynamically */ - g->irq.name = "my_gpio_irq"; - g->irq.irq_ack = my_gpio_ack_irq; - g->irq.irq_mask = my_gpio_mask_irq; - g->irq.irq_unmask = my_gpio_unmask_irq; - g->irq.irq_set_type = my_gpio_set_irq_type; + ret = devm_request_threaded_irq(dev, irq, NULL, + irq_thread_fn, IRQF_ONESHOT, "my-chip", g); + if (ret < 0) + return ret; + + /* Get a pointer to the gpio_irq_chip */ + girq = &g->gc.irq; + gpio_irq_chip_set_chip(girq, &my_gpio_irq_chip); + /* This will let us handle the parent IRQ in the driver */ + girq->parent_handler = NULL; + girq->num_parents = 0; + girq->parents = NULL; + girq->default_type = IRQ_TYPE_NONE; + girq->handler = handle_bad_irq; + + return devm_gpiochip_add_data(dev, &g->gc, g); + +The helper supports using hierarchical interrupt controllers as well. +In this case the typical set-up will look like this: + +.. code-block:: c + + /* Typical state container with dynamic irqchip */ + struct my_gpio { + struct gpio_chip gc; + struct fwnode_handle *fwnode; + }; + + static void my_gpio_mask_irq(struct irq_data *d) + { + struct gpio_chip *gc = irq_data_get_irq_chip_data(d); + irq_hw_number_t hwirq = irqd_to_hwirq(d); + + /* + * Perform any necessary action to mask the interrupt, + * and then call into the core code to synchronise the + * state. + */ + + gpiochip_disable_irq(gc, hwirq); + irq_mask_mask_parent(d); + } + + static void my_gpio_unmask_irq(struct irq_data *d) + { + struct gpio_chip *gc = irq_data_get_irq_chip_data(d); + irq_hw_number_t hwirq = irqd_to_hwirq(d); + + gpiochip_enable_irq(gc, hwirq); + + /* + * Perform any necessary action to unmask the interrupt, + * after having called into the core code to synchronise + * the state. + */ + + irq_mask_unmask_parent(d); + } + + /* + * Statically populate the irqchip. Note that it is made const + * (further indicated by the IRQCHIP_IMMUTABLE flag), and that + * the GPIOCHIP_IRQ_RESOURCE_HELPER macro adds some extra + * callbacks to the structure. + */ + static const struct irq_chip my_gpio_irq_chip = { + .name = "my_gpio_irq", + .irq_ack = my_gpio_ack_irq, + .irq_mask = my_gpio_mask_irq, + .irq_unmask = my_gpio_unmask_irq, + .irq_set_type = my_gpio_set_irq_type, + .flags = IRQCHIP_IMMUTABLE, + /* Provide the gpio resource callbacks */ + GPIOCHIP_IRQ_RESOURCE_HELPERS, + }; + + struct my_gpio *g; + struct gpio_irq_chip *girq; /* Get a pointer to the gpio_irq_chip */ girq = &g->gc.irq; - girq->chip = &g->irq; + gpio_irq_chip_set_chip(girq, &my_gpio_irq_chip); girq->default_type = IRQ_TYPE_NONE; girq->handler = handle_bad_irq; girq->fwnode = g->fwnode; @@ -488,42 +642,18 @@ In this case the typical set-up will look like this:: As you can see pretty similar, but you do not supply a parent handler for the IRQ, instead a parent irqdomain, an fwnode for the hardware and -a funcion .child_to_parent_hwirq() that has the purpose of looking up +a function .child_to_parent_hwirq() that has the purpose of looking up the parent hardware irq from a child (i.e. this gpio chip) hardware irq. As always it is good to look at examples in the kernel tree for advice on how to find the required pieces. -The old way of adding irqchips to gpiochips after registration is also still -available but we try to move away from this: - -- DEPRECATED: gpiochip_irqchip_add(): adds a chained cascaded 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-api/driver-model/design-patterns.rst) - -- gpiochip_irqchip_add_nested(): adds a nested cascaded irqchip to a gpiochip, - as discussed above regarding different types of cascaded irqchips. The - cascaded irq has to be handled by a threaded interrupt handler. - Apart from that it works exactly like the chained irqchip. - -- DEPRECATED: gpiochip_set_chained_irqchip(): sets up a chained cascaded irq - handler for a gpio_chip from a parent IRQ and passes the struct gpio_chip* - as handler data. Notice that we pass is as the handler data, since the - irqchip data is likely used by the parent irqchip. - -- gpiochip_set_nested_irqchip(): sets up a nested cascaded irq handler for a - gpio_chip from a parent IRQ. As the parent IRQ has usually been - explicitly requested by the driver, this does very little more than - mark all the child IRQs as having the other IRQ as parent. - If there is a need to exclude certain GPIO lines from the IRQ domain handled by these helpers, we can set .irq.need_valid_mask of the gpiochip before devm_gpiochip_add_data() or gpiochip_add_data() is called. This allocates an .irq.valid_mask with as many bits set as there are GPIO lines in the chip, each bit representing line 0..n-1. Drivers can exclude GPIO lines by clearing bits -from this mask. The mask must be filled in before gpiochip_irqchip_add() or -gpiochip_irqchip_add_nested() is called. +from this mask. The mask can be filled in the init_valid_mask() callback +that is part of the struct gpio_irq_chip. To use the helpers please keep the following in mind: @@ -531,13 +661,10 @@ To use the helpers please keep the following in mind: the irqchip can initialize. E.g. .dev and .can_sleep shall be set up properly. -- Nominally set all handlers to handle_bad_irq() in the setup call and pass - handle_bad_irq() as flow handler parameter in gpiochip_irqchip_add() if it is - expected for GPIO driver that irqchip .set_type() callback will be called - before using/enabling each GPIO IRQ. Then set the handler to - handle_level_irq() and/or handle_edge_irq() in the irqchip .set_type() - callback depending on what your controller supports and what is requested - by the consumer. +- Nominally set gpio_irq_chip.handler to handle_bad_irq. Then, if your irqchip + is cascaded, set the handler to handle_level_irq() and/or handle_edge_irq() + in the irqchip .set_type() callback depending on what your controller + supports and what is requested by the consumer. Locking IRQ usage @@ -592,8 +719,9 @@ When implementing an irqchip inside a GPIO driver, these two functions should typically be called in the .irq_disable() and .irq_enable() callbacks from the irqchip. -When using the gpiolib irqchip helpers, these callbacks are automatically -assigned. +When IRQCHIP_IMMUTABLE is not advertised by the irqchip, these callbacks +are automatically assigned. This behaviour is deprecated and on its way +to be removed from the kernel. Real-Time compliance for GPIO IRQ chips @@ -624,8 +752,8 @@ compliance: level and edge IRQs * [1] http://www.spinics.net/lists/linux-omap/msg120425.html -* [2] https://lkml.org/lkml/2015/9/25/494 -* [3] https://lkml.org/lkml/2015/9/25/495 +* [2] https://lore.kernel.org/r/1443209283-20781-2-git-send-email-grygorii.strashko@ti.com +* [3] https://lore.kernel.org/r/1443209283-20781-3-git-send-email-grygorii.strashko@ti.com Requesting self-owned GPIO pins |