hwspinlock updates for v5.3

This contains support for hardware spinlock TI K3 AM65x and J721E family
 of SoCs, support for using hwspinlocks from atomic context and better
 error reporting when dealing with hardware disabled in DeviceTree.
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Merge tag 'hwlock-v5.3' of git://github.com/andersson/remoteproc

Pull hwspinlock updates from Bjorn Andersson:
 "This contains support for hardware spinlock TI K3 AM65x and J721E
  family of SoCs, support for using hwspinlocks from atomic context and
  better error reporting when dealing with hardware disabled in
  DeviceTree"

* tag 'hwlock-v5.3' of git://github.com/andersson/remoteproc:
  hwspinlock: add the 'in_atomic' API
  hwspinlock: document the hwspinlock 'raw' API
  hwspinlock: stm32: implement the relax() ops
  hwspinlock: ignore disabled device
  hwspinlock/omap: Add a trace during probe
  hwspinlock/omap: Add support for TI K3 SoCs
  dt-bindings: hwlock: Update OMAP binding for TI K3 SoCs

Documentation/devicetree/bindings/hwlock/omap-hwspinlock.txt

@@ -1,12 +1,16 @@
-OMAP4+ HwSpinlock Driver
-========================
+TI HwSpinlock for OMAP and K3 based SoCs
+=========================================
 
 Required properties:
-- compatible:		Should be "ti,omap4-hwspinlock" for
+- compatible:		Should be one of the following,
+			  "ti,omap4-hwspinlock" for
 				OMAP44xx, OMAP54xx, AM33xx, AM43xx, DRA7xx SoCs
+			  "ti,am654-hwspinlock" for
+				K3 AM65x and J721E SoCs
 - reg:			Contains the hwspinlock module register address space
 			(base address and length)
 - ti,hwmods:		Name of the hwmod associated with the hwspinlock device
+			(for OMAP architecture based SoCs only)
 - #hwlock-cells:	Should be 1. The OMAP hwspinlock users will use a
 			0-indexed relative hwlock number as the argument
 			specifier value for requesting a specific hwspinlock
@@ -17,10 +21,21 @@ Please look at the generic hwlock binding for usage information for consumers,
 
 Example:
 
-/* OMAP4 */
+1. OMAP4 SoCs
 hwspinlock: spinlock@4a0f6000 {
 	compatible = "ti,omap4-hwspinlock";
 	reg = <0x4a0f6000 0x1000>;
 	ti,hwmods = "spinlock";
 	#hwlock-cells = <1>;
 };
+
+2. AM65x SoCs and J721E SoCs
+&cbass_main {
+	cbass_main_navss: interconnect0 {
+		hwspinlock: spinlock@30e00000 {
+			compatible = "ti,am654-hwspinlock";
+			reg = <0x00 0x30e00000 0x00 0x1000>;
+			#hwlock-cells = <1>;
+		};
+	};
+};

Documentation/hwspinlock.txt

@@ -134,6 +134,39 @@ notably -ETIMEDOUT if the hwspinlock is still busy after timeout msecs).
 
 The function will never sleep.
 
+::
+
+  int hwspin_lock_timeout_raw(struct hwspinlock *hwlock, unsigned int timeout);
+
+Lock a previously-assigned hwspinlock with a timeout limit (specified in
+msecs). If the hwspinlock is already taken, the function will busy loop
+waiting for it to be released, but give up when the timeout elapses.
+
+Caution: User must protect the routine of getting hardware lock with mutex
+or spinlock to avoid dead-lock, that will let user can do some time-consuming
+or sleepable operations under the hardware lock.
+
+Returns 0 when successful and an appropriate error code otherwise (most
+notably -ETIMEDOUT if the hwspinlock is still busy after timeout msecs).
+
+The function will never sleep.
+
+::
+
+  int hwspin_lock_timeout_in_atomic(struct hwspinlock *hwlock, unsigned int to);
+
+Lock a previously-assigned hwspinlock with a timeout limit (specified in
+msecs). If the hwspinlock is already taken, the function will busy loop
+waiting for it to be released, but give up when the timeout elapses.
+
+This function shall be called only from an atomic context and the timeout
+value shall not exceed a few msecs.
+
+Returns 0 when successful and an appropriate error code otherwise (most
+notably -ETIMEDOUT if the hwspinlock is still busy after timeout msecs).
+
+The function will never sleep.
+
 ::
 
   int hwspin_trylock(struct hwspinlock *hwlock);
@@ -184,6 +217,34 @@ Returns 0 on success and an appropriate error code otherwise (most
 notably -EBUSY if the hwspinlock was already taken).
 The function will never sleep.
 
+::
+
+  int hwspin_trylock_raw(struct hwspinlock *hwlock);
+
+Attempt to lock a previously-assigned hwspinlock, but immediately fail if
+it is already taken.
+
+Caution: User must protect the routine of getting hardware lock with mutex
+or spinlock to avoid dead-lock, that will let user can do some time-consuming
+or sleepable operations under the hardware lock.
+
+Returns 0 on success and an appropriate error code otherwise (most
+notably -EBUSY if the hwspinlock was already taken).
+The function will never sleep.
+
+::
+
+  int hwspin_trylock_in_atomic(struct hwspinlock *hwlock);
+
+Attempt to lock a previously-assigned hwspinlock, but immediately fail if
+it is already taken.
+
+This function shall be called only from an atomic context.
+
+Returns 0 on success and an appropriate error code otherwise (most
+notably -EBUSY if the hwspinlock was already taken).
+The function will never sleep.
+
 ::
 
   void hwspin_unlock(struct hwspinlock *hwlock);
@@ -220,6 +281,26 @@ Upon a successful return from this function, preemption is reenabled,
 and the state of the local interrupts is restored to the state saved at
 the given flags. This function will never sleep.
 
+::
+
+  void hwspin_unlock_raw(struct hwspinlock *hwlock);
+
+Unlock a previously-locked hwspinlock.
+
+The caller should **never** unlock an hwspinlock which is already unlocked.
+Doing so is considered a bug (there is no protection against this).
+This function will never sleep.
+
+::
+
+  void hwspin_unlock_in_atomic(struct hwspinlock *hwlock);
+
+Unlock a previously-locked hwspinlock.
+
+The caller should **never** unlock an hwspinlock which is already unlocked.
+Doing so is considered a bug (there is no protection against this).
+This function will never sleep.
+
 ::
 
   int hwspin_lock_get_id(struct hwspinlock *hwlock);

drivers/hwspinlock/Kconfig

@@ -9,7 +9,7 @@ menuconfig HWSPINLOCK
 config HWSPINLOCK_OMAP
 	tristate "OMAP Hardware Spinlock device"
 	depends on HWSPINLOCK
-	depends on ARCH_OMAP4 || SOC_OMAP5 || SOC_DRA7XX || SOC_AM33XX || SOC_AM43XX
+	depends on ARCH_OMAP4 || SOC_OMAP5 || SOC_DRA7XX || SOC_AM33XX || SOC_AM43XX || ARCH_K3
 	help
 	  Say y here to support the OMAP Hardware Spinlock device (firstly
 	  introduced in OMAP4).

drivers/hwspinlock/hwspinlock_core.c

@@ -9,6 +9,7 @@
 
 #define pr_fmt(fmt)    "%s: " fmt, __func__
 
+#include <linux/delay.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/spinlock.h>
@@ -23,6 +24,9 @@
 
 #include "hwspinlock_internal.h"
 
+/* retry delay used in atomic context */
+#define HWSPINLOCK_RETRY_DELAY_US	100
+
 /* radix tree tags */
 #define HWSPINLOCK_UNUSED	(0) /* tags an hwspinlock as unused */
 
@@ -68,11 +72,11 @@ static DEFINE_MUTEX(hwspinlock_tree_lock);
  * user need some time-consuming or sleepable operations under the hardware
  * lock, they need one sleepable lock (like mutex) to protect the operations.
  *
- * If the mode is not HWLOCK_RAW, upon a successful return from this function,
- * preemption (and possibly interrupts) is disabled, so the caller must not
- * sleep, and is advised to release the hwspinlock as soon as possible. This is
- * required in order to minimize remote cores polling on the hardware
- * interconnect.
+ * If the mode is neither HWLOCK_IN_ATOMIC nor HWLOCK_RAW, upon a successful
+ * return from this function, preemption (and possibly interrupts) is disabled,
+ * so the caller must not sleep, and is advised to release the hwspinlock as
+ * soon as possible. This is required in order to minimize remote cores polling
+ * on the hardware interconnect.
  *
  * The user decides whether local interrupts are disabled or not, and if yes,
  * whether he wants their previous state to be saved. It is up to the user
@@ -112,6 +116,7 @@ int __hwspin_trylock(struct hwspinlock *hwlock, int mode, unsigned long *flags)
 		ret = spin_trylock_irq(&hwlock->lock);
 		break;
 	case HWLOCK_RAW:
+	case HWLOCK_IN_ATOMIC:
 		ret = 1;
 		break;
 	default:
@@ -136,6 +141,7 @@ int __hwspin_trylock(struct hwspinlock *hwlock, int mode, unsigned long *flags)
 			spin_unlock_irq(&hwlock->lock);
 			break;
 		case HWLOCK_RAW:
+		case HWLOCK_IN_ATOMIC:
 			/* Nothing to do */
 			break;
 		default:
@@ -179,11 +185,14 @@ EXPORT_SYMBOL_GPL(__hwspin_trylock);
  * user need some time-consuming or sleepable operations under the hardware
  * lock, they need one sleepable lock (like mutex) to protect the operations.
  *
- * If the mode is not HWLOCK_RAW, upon a successful return from this function,
- * preemption is disabled (and possibly local interrupts, too), so the caller
- * must not sleep, and is advised to release the hwspinlock as soon as possible.
- * This is required in order to minimize remote cores polling on the
- * hardware interconnect.
+ * If the mode is HWLOCK_IN_ATOMIC (called from an atomic context) the timeout
+ * is handled with busy-waiting delays, hence shall not exceed few msecs.
+ *
+ * If the mode is neither HWLOCK_IN_ATOMIC nor HWLOCK_RAW, upon a successful
+ * return from this function, preemption (and possibly interrupts) is disabled,
+ * so the caller must not sleep, and is advised to release the hwspinlock as
+ * soon as possible. This is required in order to minimize remote cores polling
+ * on the hardware interconnect.
  *
  * The user decides whether local interrupts are disabled or not, and if yes,
  * whether he wants their previous state to be saved. It is up to the user
@@ -198,7 +207,7 @@ int __hwspin_lock_timeout(struct hwspinlock *hwlock, unsigned int to,
 					int mode, unsigned long *flags)
 {
 	int ret;
-	unsigned long expire;
+	unsigned long expire, atomic_delay = 0;
 
 	expire = msecs_to_jiffies(to) + jiffies;
 
@@ -212,8 +221,15 @@ int __hwspin_lock_timeout(struct hwspinlock *hwlock, unsigned int to,
 		 * The lock is already taken, let's check if the user wants
 		 * us to try again
 		 */
+		if (mode == HWLOCK_IN_ATOMIC) {
+			udelay(HWSPINLOCK_RETRY_DELAY_US);
+			atomic_delay += HWSPINLOCK_RETRY_DELAY_US;
+			if (atomic_delay > to * 1000)
+				return -ETIMEDOUT;
+		} else {
 			if (time_is_before_eq_jiffies(expire))
 				return -ETIMEDOUT;
+		}
 
 		/*
 		 * Allow platform-specific relax handlers to prevent
@@ -276,6 +292,7 @@ void __hwspin_unlock(struct hwspinlock *hwlock, int mode, unsigned long *flags)
 		spin_unlock_irq(&hwlock->lock);
 		break;
 	case HWLOCK_RAW:
+	case HWLOCK_IN_ATOMIC:
 		/* Nothing to do */
 		break;
 	default:
@@ -333,6 +350,11 @@ int of_hwspin_lock_get_id(struct device_node *np, int index)
 	if (ret)
 		return ret;
 
+	if (!of_device_is_available(args.np)) {
+		ret = -ENOENT;
+		goto out;
+	}
+
 	/* Find the hwspinlock device: we need its base_id */
 	ret = -EPROBE_DEFER;
 	rcu_read_lock();

drivers/hwspinlock/omap_hwspinlock.c

@@ -140,6 +140,9 @@ static int omap_hwspinlock_probe(struct platform_device *pdev)
 	if (ret)
 		goto reg_fail;
 
+	dev_dbg(&pdev->dev, "Registered %d locks with HwSpinlock core\n",
+		num_locks);
+
 	return 0;
 
 reg_fail:
@@ -171,6 +174,7 @@ static int omap_hwspinlock_remove(struct platform_device *pdev)
 
 static const struct of_device_id omap_hwspinlock_of_match[] = {
 	{ .compatible = "ti,omap4-hwspinlock", },
+	{ .compatible = "ti,am654-hwspinlock", },
 	{ /* end */ },
 };
 MODULE_DEVICE_TABLE(of, omap_hwspinlock_of_match);

drivers/hwspinlock/stm32_hwspinlock.c

@@ -5,6 +5,7 @@
  */
 
 #include <linux/clk.h>
+#include <linux/delay.h>
 #include <linux/hwspinlock.h>
 #include <linux/io.h>
 #include <linux/kernel.h>
@@ -42,9 +43,15 @@ static void stm32_hwspinlock_unlock(struct hwspinlock *lock)
 	writel(STM32_MUTEX_COREID, lock_addr);
 }
 
+static void stm32_hwspinlock_relax(struct hwspinlock *lock)
+{
+	ndelay(50);
+}
+
 static const struct hwspinlock_ops stm32_hwspinlock_ops = {
 	.trylock	= stm32_hwspinlock_trylock,
 	.unlock		= stm32_hwspinlock_unlock,
+	.relax		= stm32_hwspinlock_relax,
 };
 
 static int stm32_hwspinlock_probe(struct platform_device *pdev)

include/linux/hwspinlock.h

@@ -17,6 +17,7 @@
 #define HWLOCK_IRQSTATE		0x01 /* Disable interrupts, save state */
 #define HWLOCK_IRQ		0x02 /* Disable interrupts, don't save state */
 #define HWLOCK_RAW		0x03
+#define HWLOCK_IN_ATOMIC	0x04 /* Called while in atomic context */
 
 struct device;
 struct device_node;
@@ -222,6 +223,23 @@ static inline int hwspin_trylock_raw(struct hwspinlock *hwlock)
 	return __hwspin_trylock(hwlock, HWLOCK_RAW, NULL);
 }
 
+/**
+ * hwspin_trylock_in_atomic() - attempt to lock a specific hwspinlock
+ * @hwlock: an hwspinlock which we want to trylock
+ *
+ * This function attempts to lock an hwspinlock, and will immediately fail
+ * if the hwspinlock is already taken.
+ *
+ * This function shall be called only from an atomic context.
+ *
+ * Returns 0 if we successfully locked the hwspinlock, -EBUSY if
+ * the hwspinlock was already taken, and -EINVAL if @hwlock is invalid.
+ */
+static inline int hwspin_trylock_in_atomic(struct hwspinlock *hwlock)
+{
+	return __hwspin_trylock(hwlock, HWLOCK_IN_ATOMIC, NULL);
+}
+
 /**
  * hwspin_trylock() - attempt to lock a specific hwspinlock
  * @hwlock: an hwspinlock which we want to trylock
@@ -312,6 +330,28 @@ int hwspin_lock_timeout_raw(struct hwspinlock *hwlock, unsigned int to)
 	return __hwspin_lock_timeout(hwlock, to, HWLOCK_RAW, NULL);
 }
 
+/**
+ * hwspin_lock_timeout_in_atomic() - lock an hwspinlock with timeout limit
+ * @hwlock: the hwspinlock to be locked
+ * @to: timeout value in msecs
+ *
+ * This function locks the underlying @hwlock. If the @hwlock
+ * is already taken, the function will busy loop waiting for it to
+ * be released, but give up when @timeout msecs have elapsed.
+ *
+ * This function shall be called only from an atomic context and the timeout
+ * value shall not exceed a few msecs.
+ *
+ * Returns 0 when the @hwlock was successfully taken, and an appropriate
+ * error code otherwise (most notably an -ETIMEDOUT if the @hwlock is still
+ * busy after @timeout msecs). The function will never sleep.
+ */
+static inline
+int hwspin_lock_timeout_in_atomic(struct hwspinlock *hwlock, unsigned int to)
+{
+	return __hwspin_lock_timeout(hwlock, to, HWLOCK_IN_ATOMIC, NULL);
+}
+
 /**
  * hwspin_lock_timeout() - lock an hwspinlock with timeout limit
  * @hwlock: the hwspinlock to be locked
@@ -386,6 +426,21 @@ static inline void hwspin_unlock_raw(struct hwspinlock *hwlock)
 	__hwspin_unlock(hwlock, HWLOCK_RAW, NULL);
 }
 
+/**
+ * hwspin_unlock_in_atomic() - unlock hwspinlock
+ * @hwlock: a previously-acquired hwspinlock which we want to unlock
+ *
+ * This function will unlock a specific hwspinlock.
+ *
+ * @hwlock must be already locked (e.g. by hwspin_trylock()) before calling
+ * this function: it is a bug to call unlock on a @hwlock that is already
+ * unlocked.
+ */
+static inline void hwspin_unlock_in_atomic(struct hwspinlock *hwlock)
+{
+	__hwspin_unlock(hwlock, HWLOCK_IN_ATOMIC, NULL);
+}
+
 /**
  * hwspin_unlock() - unlock hwspinlock
  * @hwlock: a previously-acquired hwspinlock which we want to unlock