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>
diff --git a/Documentation/gpio/driver.txt b/Documentation/gpio/driver.txt
index 368d5a2..747c721 100644
--- a/Documentation/gpio/driver.txt
+++ b/Documentation/gpio/driver.txt
@@ -175,8 +175,8 @@
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 @@
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:
+ 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 tc3589x_gpio_irq(int irq, void *data)
+ 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 @@
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 @@
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 @@
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
---------------------------------------