[PATCH v4 2/4] drivers: hwspinlock: add OMAP implementation

[Ohad Ben-Cohen]

From: Simon Que <sque@xxxxxx>

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@xxxxxxxxxx: adapt to hwspinlock framework, tidy up]
Signed-off-by: Simon Que <sque@xxxxxx>
Signed-off-by: Hari Kanigeri <h-kanigeri2@xxxxxx>
Signed-off-by: Krishnamoorthy, Balaji T <balajitk@xxxxxx>
Signed-off-by: Ohad Ben-Cohen <ohad@xxxxxxxxxx>
Cc: Benoit Cousson <b-cousson@xxxxxx>
Cc: Kevin Hilman <khilman@xxxxxx>
Cc: Grant Likely <grant.likely@xxxxxxxxxxxx>
Cc: Arnd Bergmann <arnd@xxxxxxxx>
Cc: Paul Walmsley <paul@xxxxxxxxx>
Acked-by: Tony Lindgren <tony@xxxxxxxxxxx>
---
 drivers/hwspinlock/Kconfig           |    9 ++
 drivers/hwspinlock/Makefile          |    1 +
 drivers/hwspinlock/omap_hwspinlock.c |  231 ++++++++++++++++++++++++++++++++++
 3 files changed, 241 insertions(+), 0 deletions(-)
 create mode 100644 drivers/hwspinlock/omap_hwspinlock.c

diff --git a/drivers/hwspinlock/Kconfig b/drivers/hwspinlock/Kconfig
index 9dd8db4..eb4af28 100644
--- a/drivers/hwspinlock/Kconfig
+++ b/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.
diff --git a/drivers/hwspinlock/Makefile b/drivers/hwspinlock/Makefile
index b9d2b9f..5729a3f 100644
--- a/drivers/hwspinlock/Makefile
+++ b/drivers/hwspinlock/Makefile
@@ -3,3 +3,4 @@
 #
 
 obj-$(CONFIG_HWSPINLOCK)		+= hwspinlock_core.o
+obj-$(CONFIG_HWSPINLOCK_OMAP)		+= omap_hwspinlock.o
diff --git a/drivers/hwspinlock/omap_hwspinlock.c b/drivers/hwspinlock/omap_hwspinlock.c
new file mode 100644
index 0000000..03e1d60
--- /dev/null
+++ b/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@xxxxxx>
+ *          Hari Kanigeri <h-kanigeri2@xxxxxx>
+ *          Ohad Ben-Cohen <ohad@xxxxxxxxxx>
+ *
+ * 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.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@xxxxxx>");
+MODULE_AUTHOR("Hari Kanigeri <h-kanigeri2@xxxxxx>");
+MODULE_AUTHOR("Ohad Ben-Cohen <ohad@xxxxxxxxxx>");
-- 
1.7.1

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