diff options
author | Linus Walleij <linus.walleij@linaro.org> | 2016-11-24 12:57:25 +0300 |
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committer | Linus Walleij <linus.walleij@linaro.org> | 2016-11-25 17:12:27 +0300 |
commit | d245b3f9bd36f02fd641cba9931d8b4c77126e74 (patch) | |
tree | fa9984376f28c4f6b8883aff8a704178aa68412f /Documentation | |
parent | 07d9a380680d1c0eb51ef87ff2eab5c994949e69 (diff) | |
download | linux-d245b3f9bd36f02fd641cba9931d8b4c77126e74.tar.xz |
gpio: simplify adding threaded interrupts
This tries to simplify the use of CONFIG_GPIOLIB_IRQCHIP when
using threaded interrupts: add a new call
gpiochip_irqchip_add_nested() to indicate that we're dealing
with a nested rather than a chained irqchip, then create a
separate gpiochip_set_nested_irqchip() to mirror
the gpiochip_set_chained_irqchip() call to connect the
parent and child interrupts.
In the nested case gpiochip_set_nested_irqchip() does nothing
more than call irq_set_parent() on each valid child interrupt,
which has little semantic effect in the kernel, but this is
probably still formally correct.
Update all drivers using nested interrupts to use
gpiochip_irqchip_add_nested() so we can now see clearly
which these users are.
The DLN2 driver can drop its specific hack with
.irq_not_threaded as we now recognize whether a chip is
threaded or not from its use of gpiochip_irqchip_add_nested()
signature rather than from inspecting .can_sleep.
We rename the .irq_parent to .irq_chained_parent since this
parent IRQ is only really kept around for the chained
interrupt handlers.
Cc: Lars Poeschel <poeschel@lemonage.de>
Cc: Octavian Purdila <octavian.purdila@intel.com>
Cc: Daniel Baluta <daniel.baluta@intel.com>
Cc: Bin Gao <bin.gao@linux.intel.com>
Cc: Mika Westerberg <mika.westerberg@linux.intel.com>
Cc: Ajay Thomas <ajay.thomas.david.rajamanickam@intel.com>
Cc: Semen Protsenko <semen.protsenko@globallogic.com>
Cc: Alexander Stein <alexander.stein@systec-electronic.com>
Cc: Phil Reid <preid@electromag.com.au>
Cc: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Cc: Patrice Chotard <patrice.chotard@st.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Diffstat (limited to 'Documentation')
-rw-r--r-- | Documentation/gpio/driver.txt | 62 |
1 files changed, 36 insertions, 26 deletions
diff --git a/Documentation/gpio/driver.txt b/Documentation/gpio/driver.txt index 368d5a294d89..747c721776ed 100644 --- a/Documentation/gpio/driver.txt +++ b/Documentation/gpio/driver.txt @@ -175,8 +175,8 @@ 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. -RT_FULL: GPIO driver should not use spinlock_t or any sleepable APIs -(like PM runtime) as part of its irq_chip implementation on -RT. +RT_FULL: a realtime compliant GPIO driver should not use spinlock_t or any +sleepable APIs (like PM runtime) as part of its irq_chip implementation. - spinlock_t should be replaced with raw_spinlock_t [1]. - If sleepable APIs have to be used, these can be done from the .irq_bus_lock() and .irq_bus_unlock() callbacks, as these are the only slowpath callbacks @@ -185,33 +185,32 @@ RT_FULL: GPIO driver should not use spinlock_t or any sleepable APIs 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 + an SoC. This means that there is a fast IRQ flow 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) + system interrupt controller. This means that 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 foo_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. + struct gpio_chip, as everything happens directly in the callbacks: no + slow bus traffic like I2C can be used. RT_FULL: Note, chained IRQ handlers will not be forced threaded on -RT. As result, spinlock_t or any sleepable APIs (like PM runtime) can't be used in chained IRQ handler. - if required (and if it can't be converted to the nested threaded GPIO irqchip) - - chained IRQ handler can be converted to generic irq handler and this way - it will be threaded IRQ handler on -RT and hard IRQ handler on non-RT + If required (and if it can't be converted to the nested threaded GPIO irqchip) + a chained IRQ handler can be converted to generic irq handler and this way + it will be a threaded IRQ handler on -RT and a hard IRQ handler on non-RT (for example, see [3]). Know W/A: The generic_handle_irq() is expected to be called with IRQ disabled, - so IRQ core will complain if it will be called from IRQ handler which is - forced thread. The "fake?" raw lock can be used to W/A this problem: + so the IRQ core will complain if it is called from an IRQ handler which is + forced to a thread. The "fake?" raw lock can be used to W/A this problem: raw_spinlock_t wa_lock; static irqreturn_t omap_gpio_irq_handler(int irq, void *gpiobank) @@ -243,7 +242,7 @@ GPIO irqchips usually fall in one of two categories: 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) + static irqreturn_t foo_gpio_irq(int irq, void *data) ... handle_nested_irq(irq); @@ -256,23 +255,31 @@ 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 +* gpiochip_irqchip_add(): adds a chained 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) - If there is a need to exclude certain GPIOs from the IRQ domain, one can - set .irq_need_valid_mask of the gpiochip before gpiochip_add_data() is - called. This allocates .irq_valid_mask with as many bits set as there are - GPIOs in the chip. Drivers can exclude GPIOs by clearing bits from this - mask. The mask must be filled in before gpiochip_irqchip_add() is called. +* gpiochip_irqchip_add_nested(): adds a nested irqchip to a gpiochip. + Apart from that it works exactly like the chained irqchip. * 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. This is also used - to set up a nested irqchip if NULL is passed as handler. + parent irqchip!). + +* gpiochip_set_nested_irqchip(): sets up a nested 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 GPIOs from the IRQ domain, you can +set .irq_need_valid_mask of the gpiochip before gpiochip_add_data() is +called. This allocates an .irq_valid_mask with as many bits set as there +are GPIOs in the chip. Drivers can exclude GPIOs by clearing bits from this +mask. The mask must be filled in before gpiochip_irqchip_add() or +gpiochip_irqchip_add_nested() is called. To use the helpers please keep the following in mind: @@ -323,6 +330,9 @@ When implementing an irqchip inside a GPIO driver, these two functions should typically be called in the .startup() and .shutdown() callbacks from the irqchip. +When using the gpiolib irqchip helpers, these callback are automatically +assigned. + Real-Time compliance for GPIO IRQ chips --------------------------------------- |