Merge tag 'gpio-updates-for-v6.9-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/brgl/linux

Pull gpio updates from Bartosz Golaszewski:
 "The biggest feature is the locking overhaul. Up until now the
  synchronization in the GPIO subsystem was broken. There was a single
  spinlock "protecting" multiple data structures but doing it wrong (as
  evidenced by several places where it would be released when a sleeping
  function was called and then reacquired without checking the protected
  state).

  We tried to use an RW semaphore before but the main issue with GPIO is
  that we have drivers implementing the interfaces in both sleeping and
  non-sleeping ways as well as user-facing interfaces that can be called
  both from process as well as atomic contexts. Both ends converge in
  the same code paths that can use neither spinlocks nor mutexes. The
  only reasonable way out is to use SRCU and go mostly lockless. To that
  end: we add several SRCU structs in relevant places and use them to
  assure consistency between API calls together with atomic reads and
  writes of GPIO descriptor flags where it makes sense.

  This code has spent several weeks in next and has received several
  fixes in the first week or two after which it stabilized nicely. The
  GPIO subsystem is now resilient to providers being suddenly unbound.
  We managed to also remove the existing character device RW semaphore
  and the obsolete global spinlock.

  Other than the locking rework we have one new driver (for Chromebook
  EC), much appreciated documentation improvements from Kent and the
  regular driver improvements, DT-bindings updates and GPIOLIB core
  tweaks.

  Serialization rework:
   - use SRCU to serialize access to the global GPIO device list, to
     GPIO device structs themselves and to GPIO descriptors
   - make the GPIO subsystem resilient to the GPIO providers being
     unbound while the API calls are in progress
   - don't dereference the SRCU-protected chip pointer if the
     information we need can be obtained from the GPIO device structure
   - move some of the information contained in struct gpio_chip to
     struct gpio_device to further reduce the need to dereference the
     former
   - pass the GPIO device struct instead of the GPIO chip to sysfs
     callback to, again, reduce the need for accessing the latter
   - get GPIO descriptors from the GPIO device, not from the chip for
     the same reason
   - allow for mostly lockless operation of the GPIO driver API: assure
     consistency with SRCU and atomic operations
   - remove the global GPIO spinlock
   - remove the character device RW semaphore

  Core GPIOLIB:
   - constify pointers in GPIO API where applicable
   - unify the GPIO counting APIs for ACPI and OF
   - provide a macro for iterating over all GPIOs, not only the ones
     that are requested
   - remove leftover typedefs
   - pass the consumer device to GPIO core in
     devm_fwnode_gpiod_get_index() for improved logging
   - constify the GPIO bus type
   - don't warn about removing GPIO chips with descriptors still held by
     users as we can now handle this situation gracefully
   - remove unused logging helpers
   - unexport functions that are only used internally in the GPIO
     subsystem
   - set the device type (assign the relevant struct device_type) for
     GPIO devices

  New drivers:
   - add the ChromeOS EC GPIO driver

  Driver improvements:
   - allow building gpio-vf610 with COMPILE_TEST as well as disabling it
     in menuconfig (before it was always built for i.MX cofigs)
   - count the number of EICs using the device properties instead of
     hard-coding it in gpio-eic-sprd
   - improve the device naming, extend the debugfs output and add
     lockdep asserts to gpio-sim

  DT bindings:
   - document the 'label' property for gpio-pca9570
   - convert aspeed,ast2400-gpio bindings to DT schema
   - disallow unevaluated properties for gpio-mvebu
   - document a new model in renesas,rcar-gpio

  Documentation:
   - improve the character device kerneldocs in user-space headers
   - add proper documentation for the character device uAPI (both v1 and v2)
   - move the sysfs and gpio-mockup docs into the "obsolete" section
   - improve naming consistency for GPIO terms
   - clarify the line values description for sysfs
   - minor docs improvements
   - improve the driver API contract for setting GPIO direction
   - mark unsafe APIs as deprecated in kerneldocs and suggest
     replacements

  Other:
   - remove an obsolete test from selftests"

* tag 'gpio-updates-for-v6.9-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/brgl/linux: (79 commits)
  gpio: sysfs: repair export returning -EPERM on 1st attempt
  selftest: gpio: remove obsolete gpio-mockup test
  gpiolib: Deduplicate cleanup for-loop in gpiochip_add_data_with_key()
  dt-bindings: gpio: aspeed,ast2400-gpio: Convert to DT schema
  gpio: acpi: Make acpi_gpio_count() take firmware node as a parameter
  gpio: of: Make of_gpio_get_count() take firmware node as a parameter
  gpiolib: Pass consumer device through to core in devm_fwnode_gpiod_get_index()
  gpio: sim: use for_each_hwgpio()
  gpio: provide for_each_hwgpio()
  gpio: don't warn about removing GPIO chips with active users anymore
  gpio: sim: delimit the fwnode name with a ":" when generating labels
  gpio: sim: add lockdep asserts
  gpio: Add ChromeOS EC GPIO driver
  gpio: constify of_phandle_args in of_find_gpio_device_by_xlate()
  gpio: fix memory leak in gpiod_request_commit()
  gpio: constify opaque pointer "data" in gpio_device_find()
  gpio: cdev: fix a NULL-pointer dereference with DEBUG enabled
  gpio: uapi: clarify default_values being logical
  gpio: sysfs: fix inverted pointer logic
  gpio: don't let lockdep complain about inherently dangerous RCU usage
  ...

1 files changed, 63 insertions, 32 deletions

diff --git a/drivers/gpio/gpiolib.h b/drivers/gpio/gpiolib.h
index a4a2520b5f31..f67d5991ab1c 100644
--- a/drivers/gpio/gpiolib.h
+++ b/drivers/gpio/gpiolib.h
@@ -16,7 +16,7 @@
 #include <linux/gpio/driver.h>
 #include <linux/module.h>
 #include <linux/notifier.h>
-#include <linux/rwsem.h>
+#include <linux/srcu.h>
 
 #define GPIOCHIP_NAME	"gpiochip"
 
@@ -33,6 +33,8 @@
  * @descs: array of ngpio descriptors.
  * @ngpio: the number of GPIO lines on this GPIO device, equal to the size
  * of the @descs array.
+ * @can_sleep: indicate whether the GPIO chip driver's callbacks can sleep
+ * implying that they cannot be used from atomic context
  * @base: GPIO base in the DEPRECATED global Linux GPIO numberspace, assigned
  * at device creation time.
  * @label: a descriptive name for the GPIO device, such as the part number
@@ -43,9 +45,7 @@
  *                       requested, released or reconfigured
  * @device_notifier: used to notify character device wait queues about the GPIO
  *                   device being unregistered
- * @sem: protects the structure from a NULL-pointer dereference of @chip by
- *       user-space operations when the device gets unregistered during
- *       a hot-unplug event
+ * @srcu: protects the pointer to the underlying GPIO chip
  * @pin_ranges: range of pins served by the GPIO driver
  *
  * This state container holds most of the runtime variable data
@@ -59,16 +59,17 @@ struct gpio_device {
 	int			id;
 	struct device		*mockdev;
 	struct module		*owner;
-	struct gpio_chip	*chip;
+	struct gpio_chip __rcu	*chip;
 	struct gpio_desc	*descs;
 	int			base;
 	u16			ngpio;
+	bool			can_sleep;
 	const char		*label;
 	void			*data;
 	struct list_head        list;
 	struct blocking_notifier_head line_state_notifier;
 	struct blocking_notifier_head device_notifier;
-	struct rw_semaphore	sem;
+	struct srcu_struct	srcu;
 
 #ifdef CONFIG_PINCTRL
 	/*
@@ -134,9 +135,6 @@ int gpiod_set_array_value_complex(bool raw, bool can_sleep,
 
 int gpiod_set_transitory(struct gpio_desc *desc, bool transitory);
 
-extern spinlock_t gpio_lock;
-extern struct list_head gpio_devices;
-
 void gpiod_line_state_notify(struct gpio_desc *desc, unsigned long action);
 
 /**
@@ -147,6 +145,7 @@ void gpiod_line_state_notify(struct gpio_desc *desc, unsigned long action);
  * @label:		Name of the consumer
  * @name:		Line name
  * @hog:		Pointer to the device node that hogs this line (if any)
+ * @srcu:		SRCU struct protecting the label pointer.
  *
  * These are obtained using gpiod_get() and are preferable to the old
  * integer-based handles.
@@ -178,16 +177,38 @@ struct gpio_desc {
 #define FLAG_EVENT_CLOCK_HTE		19 /* GPIO CDEV reports hardware timestamps in events */
 
 	/* Connection label */
-	const char		*label;
+	const char __rcu	*label;
 	/* Name of the GPIO */
 	const char		*name;
 #ifdef CONFIG_OF_DYNAMIC
 	struct device_node	*hog;
 #endif
+	struct srcu_struct	srcu;
 };
 
 #define gpiod_not_found(desc)		(IS_ERR(desc) && PTR_ERR(desc) == -ENOENT)
 
+struct gpio_chip_guard {
+	struct gpio_device *gdev;
+	struct gpio_chip *gc;
+	int idx;
+};
+
+DEFINE_CLASS(gpio_chip_guard,
+	     struct gpio_chip_guard,
+	     srcu_read_unlock(&_T.gdev->srcu, _T.idx),
+	     ({
+		struct gpio_chip_guard _guard;
+
+		_guard.gdev = desc->gdev;
+		_guard.idx = srcu_read_lock(&_guard.gdev->srcu);
+		_guard.gc = srcu_dereference(_guard.gdev->chip,
+					     &_guard.gdev->srcu);
+
+		_guard;
+	     }),
+	     struct gpio_desc *desc)
+
 int gpiod_request(struct gpio_desc *desc, const char *label);
 void gpiod_free(struct gpio_desc *desc);
 
@@ -202,12 +223,21 @@ static inline int gpiod_request_user(struct gpio_desc *desc, const char *label)
 	return ret;
 }
 
+struct gpio_desc *gpiod_find_and_request(struct device *consumer,
+					 struct fwnode_handle *fwnode,
+					 const char *con_id,
+					 unsigned int idx,
+					 enum gpiod_flags flags,
+					 const char *label,
+					 bool platform_lookup_allowed);
+
 int gpiod_configure_flags(struct gpio_desc *desc, const char *con_id,
 		unsigned long lflags, enum gpiod_flags dflags);
 int gpio_set_debounce_timeout(struct gpio_desc *desc, unsigned int debounce);
 int gpiod_hog(struct gpio_desc *desc, const char *name,
 		unsigned long lflags, enum gpiod_flags dflags);
 int gpiochip_get_ngpios(struct gpio_chip *gc, struct device *dev);
+const char *gpiod_get_label(struct gpio_desc *desc);
 
 /*
  * Return the GPIO number of the passed descriptor relative to its chip
@@ -219,31 +249,32 @@ static inline int gpio_chip_hwgpio(const struct gpio_desc *desc)
 
 /* With descriptor prefix */
 
-#define gpiod_emerg(desc, fmt, ...)					       \
-	pr_emerg("gpio-%d (%s): " fmt, desc_to_gpio(desc), desc->label ? : "?",\
-		 ##__VA_ARGS__)
-#define gpiod_crit(desc, fmt, ...)					       \
-	pr_crit("gpio-%d (%s): " fmt, desc_to_gpio(desc), desc->label ? : "?", \
-		 ##__VA_ARGS__)
-#define gpiod_err(desc, fmt, ...)					       \
-	pr_err("gpio-%d (%s): " fmt, desc_to_gpio(desc), desc->label ? : "?",  \
-		 ##__VA_ARGS__)
-#define gpiod_warn(desc, fmt, ...)					       \
-	pr_warn("gpio-%d (%s): " fmt, desc_to_gpio(desc), desc->label ? : "?", \
-		 ##__VA_ARGS__)
-#define gpiod_info(desc, fmt, ...)					       \
-	pr_info("gpio-%d (%s): " fmt, desc_to_gpio(desc), desc->label ? : "?", \
-		 ##__VA_ARGS__)
-#define gpiod_dbg(desc, fmt, ...)					       \
-	pr_debug("gpio-%d (%s): " fmt, desc_to_gpio(desc), desc->label ? : "?",\
-		 ##__VA_ARGS__)
+#define gpiod_err(desc, fmt, ...) \
+do { \
+	scoped_guard(srcu, &desc->srcu) { \
+		pr_err("gpio-%d (%s): " fmt, desc_to_gpio(desc), \
+		       gpiod_get_label(desc) ? : "?", ##__VA_ARGS__); \
+	} \
+} while (0)
+
+#define gpiod_warn(desc, fmt, ...) \
+do { \
+	scoped_guard(srcu, &desc->srcu) { \
+		pr_warn("gpio-%d (%s): " fmt, desc_to_gpio(desc), \
+			gpiod_get_label(desc) ? : "?", ##__VA_ARGS__); \
+	} \
+} while (0)
+
+#define gpiod_dbg(desc, fmt, ...) \
+do { \
+	scoped_guard(srcu, &desc->srcu) { \
+		pr_debug("gpio-%d (%s): " fmt, desc_to_gpio(desc), \
+			 gpiod_get_label(desc) ? : "?", ##__VA_ARGS__); \
+	} \
+} while (0)
 
 /* With chip prefix */
 
-#define chip_emerg(gc, fmt, ...)					\
-	dev_emerg(&gc->gpiodev->dev, "(%s): " fmt, gc->label, ##__VA_ARGS__)
-#define chip_crit(gc, fmt, ...)					\
-	dev_crit(&gc->gpiodev->dev, "(%s): " fmt, gc->label, ##__VA_ARGS__)
 #define chip_err(gc, fmt, ...)					\
 	dev_err(&gc->gpiodev->dev, "(%s): " fmt, gc->label, ##__VA_ARGS__)
 #define chip_warn(gc, fmt, ...)					\