drivers: hwspinlock: add OMAP implementation

Add hwspinlock support for the OMAP4 Hardware Spinlock device.

The Hardware Spinlock device on OMAP4 provides hardware assistance
for synchronization between the multiple processors in the system
(dual Cortex-A9, dual Cortex-M3 and a C64x+ DSP).

[ohad@wizery.com: adapt to hwspinlock framework, tidy up]
Signed-off-by: Simon Que <sque@ti.com>
Signed-off-by: Hari Kanigeri <h-kanigeri2@ti.com>
Signed-off-by: Krishnamoorthy, Balaji T <balajitk@ti.com>
Signed-off-by: Ohad Ben-Cohen <ohad@wizery.com>
Cc: Benoit Cousson <b-cousson@ti.com>
Cc: Kevin Hilman <khilman@ti.com>
Cc: Grant Likely <grant.likely@secretlab.ca>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Paul Walmsley <paul@pwsan.com>
Cc: Russell King <linux@arm.linux.org.uk>
Signed-off-by: Tony Lindgren <tony@atomide.com>

drivers/hwspinlock/Kconfig

@@ -11,3 +11,12 @@ config HWSPINLOCK
 	  coprocessors).
 
 	  If unsure, say N.
+
+config HWSPINLOCK_OMAP
+	tristate "OMAP Hardware Spinlock device"
+	depends on HWSPINLOCK && ARCH_OMAP4
+	help
+	  Say y here to support the OMAP Hardware Spinlock device (firstly
+	  introduced in OMAP4).
+
+	  If unsure, say N.

drivers/hwspinlock/Makefile

@@ -3,3 +3,4 @@
 #
 
 obj-$(CONFIG_HWSPINLOCK)		+= hwspinlock_core.o
+obj-$(CONFIG_HWSPINLOCK_OMAP)		+= omap_hwspinlock.o

drivers/hwspinlock/omap_hwspinlock.c

@@ -0,0 +1,231 @@
+/*
+ * OMAP hardware spinlock driver
+ *
+ * Copyright (C) 2010 Texas Instruments Incorporated - http://www.ti.com
+ *
+ * Contact: Simon Que <sque@ti.com>
+ *          Hari Kanigeri <h-kanigeri2@ti.com>
+ *          Ohad Ben-Cohen <ohad@wizery.com>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * version 2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/device.h>
+#include <linux/delay.h>
+#include <linux/io.h>
+#include <linux/bitops.h>
+#include <linux/pm_runtime.h>
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+#include <linux/hwspinlock.h>
+#include <linux/platform_device.h>
+
+#include "hwspinlock_internal.h"
+
+/* Spinlock register offsets */
+#define SYSSTATUS_OFFSET		0x0014
+#define LOCK_BASE_OFFSET		0x0800
+
+#define SPINLOCK_NUMLOCKS_BIT_OFFSET	(24)
+
+/* Possible values of SPINLOCK_LOCK_REG */
+#define SPINLOCK_NOTTAKEN		(0)	/* free */
+#define SPINLOCK_TAKEN			(1)	/* locked */
+
+#define to_omap_hwspinlock(lock)	\
+	container_of(lock, struct omap_hwspinlock, lock)
+
+struct omap_hwspinlock {
+	struct hwspinlock lock;
+	void __iomem *addr;
+};
+
+struct omap_hwspinlock_state {
+	int num_locks;			/* Total number of locks in system */
+	void __iomem *io_base;		/* Mapped base address */
+};
+
+static int omap_hwspinlock_trylock(struct hwspinlock *lock)
+{
+	struct omap_hwspinlock *omap_lock = to_omap_hwspinlock(lock);
+
+	/* attempt to acquire the lock by reading its value */
+	return (SPINLOCK_NOTTAKEN == readl(omap_lock->addr));
+}
+
+static void omap_hwspinlock_unlock(struct hwspinlock *lock)
+{
+	struct omap_hwspinlock *omap_lock = to_omap_hwspinlock(lock);
+
+	/* release the lock by writing 0 to it */
+	writel(SPINLOCK_NOTTAKEN, omap_lock->addr);
+}
+
+/*
+ * relax the OMAP interconnect while spinning on it.
+ *
+ * The specs recommended that the retry delay time will be
+ * just over half of the time that a requester would be
+ * expected to hold the lock.
+ *
+ * The number below is taken from an hardware specs example,
+ * obviously it is somewhat arbitrary.
+ */
+static void omap_hwspinlock_relax(struct hwspinlock *lock)
+{
+	ndelay(50);
+}
+
+static const struct hwspinlock_ops omap_hwspinlock_ops = {
+	.trylock = omap_hwspinlock_trylock,
+	.unlock = omap_hwspinlock_unlock,
+	.relax = omap_hwspinlock_relax,
+};
+
+static int __devinit omap_hwspinlock_probe(struct platform_device *pdev)
+{
+	struct omap_hwspinlock *omap_lock;
+	struct omap_hwspinlock_state *state;
+	struct hwspinlock *lock;
+	struct resource *res;
+	void __iomem *io_base;
+	int i, ret;
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	if (!res)
+		return -ENODEV;
+
+	state = kzalloc(sizeof(*state), GFP_KERNEL);
+	if (!state)
+		return -ENOMEM;
+
+	io_base = ioremap(res->start, resource_size(res));
+	if (!io_base) {
+		ret = -ENOMEM;
+		goto free_state;
+	}
+
+	/* Determine number of locks */
+	i = readl(io_base + SYSSTATUS_OFFSET);
+	i >>= SPINLOCK_NUMLOCKS_BIT_OFFSET;
+
+	/* one of the four lsb's must be set, and nothing else */
+	if (hweight_long(i & 0xf) != 1 || i > 8) {
+		ret = -EINVAL;
+		goto iounmap_base;
+	}
+
+	state->num_locks = i * 32;
+	state->io_base = io_base;
+
+	platform_set_drvdata(pdev, state);
+
+	/*
+	 * runtime PM will make sure the clock of this module is
+	 * enabled iff at least one lock is requested
+	 */
+	pm_runtime_enable(&pdev->dev);
+
+	for (i = 0; i < state->num_locks; i++) {
+		omap_lock = kzalloc(sizeof(*omap_lock), GFP_KERNEL);
+		if (!omap_lock) {
+			ret = -ENOMEM;
+			goto free_locks;
+		}
+
+		omap_lock->lock.dev = &pdev->dev;
+		omap_lock->lock.owner = THIS_MODULE;
+		omap_lock->lock.id = i;
+		omap_lock->lock.ops = &omap_hwspinlock_ops;
+		omap_lock->addr = io_base + LOCK_BASE_OFFSET + sizeof(u32) * i;
+
+		ret = hwspin_lock_register(&omap_lock->lock);
+		if (ret) {
+			kfree(omap_lock);
+			goto free_locks;
+		}
+	}
+
+	return 0;
+
+free_locks:
+	while (--i >= 0) {
+		lock = hwspin_lock_unregister(i);
+		/* this should't happen, but let's give our best effort */
+		if (!lock) {
+			dev_err(&pdev->dev, "%s: cleanups failed\n", __func__);
+			continue;
+		}
+		omap_lock = to_omap_hwspinlock(lock);
+		kfree(omap_lock);
+	}
+	pm_runtime_disable(&pdev->dev);
+iounmap_base:
+	iounmap(io_base);
+free_state:
+	kfree(state);
+	return ret;
+}
+
+static int omap_hwspinlock_remove(struct platform_device *pdev)
+{
+	struct omap_hwspinlock_state *state = platform_get_drvdata(pdev);
+	struct hwspinlock *lock;
+	struct omap_hwspinlock *omap_lock;
+	int i;
+
+	for (i = 0; i < state->num_locks; i++) {
+		lock = hwspin_lock_unregister(i);
+		/* this shouldn't happen at this point. if it does, at least
+		 * don't continue with the remove */
+		if (!lock) {
+			dev_err(&pdev->dev, "%s: failed on %d\n", __func__, i);
+			return -EBUSY;
+		}
+
+		omap_lock = to_omap_hwspinlock(lock);
+		kfree(omap_lock);
+	}
+
+	pm_runtime_disable(&pdev->dev);
+	iounmap(state->io_base);
+	kfree(state);
+
+	return 0;
+}
+
+static struct platform_driver omap_hwspinlock_driver = {
+	.probe		= omap_hwspinlock_probe,
+	.remove		= omap_hwspinlock_remove,
+	.driver		= {
+		.name	= "omap_hwspinlock",
+	},
+};
+
+static int __init omap_hwspinlock_init(void)
+{
+	return platform_driver_register(&omap_hwspinlock_driver);
+}
+/* board init code might need to reserve hwspinlocks for predefined purposes */
+postcore_initcall(omap_hwspinlock_init);
+
+static void __exit omap_hwspinlock_exit(void)
+{
+	platform_driver_unregister(&omap_hwspinlock_driver);
+}
+module_exit(omap_hwspinlock_exit);
+
+MODULE_LICENSE("GPL v2");
+MODULE_DESCRIPTION("Hardware spinlock driver for OMAP");
+MODULE_AUTHOR("Simon Que <sque@ti.com>");
+MODULE_AUTHOR("Hari Kanigeri <h-kanigeri2@ti.com>");
+MODULE_AUTHOR("Ohad Ben-Cohen <ohad@wizery.com>");