Adding upstream version 5.10.209.upstream/5.10.209upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 831 insertions, 0 deletions

diff --git a/drivers/amba/bus.c b/drivers/amba/bus.c
new file mode 100644
index 000000000..52ab58293
--- /dev/null
+++ b/drivers/amba/bus.c
@@ -0,0 +1,831 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ *  linux/arch/arm/common/amba.c
+ *
+ *  Copyright (C) 2003 Deep Blue Solutions Ltd, All Rights Reserved.
+ */
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/device.h>
+#include <linux/string.h>
+#include <linux/slab.h>
+#include <linux/io.h>
+#include <linux/pm.h>
+#include <linux/pm_runtime.h>
+#include <linux/pm_domain.h>
+#include <linux/amba/bus.h>
+#include <linux/sizes.h>
+#include <linux/limits.h>
+#include <linux/clk/clk-conf.h>
+#include <linux/platform_device.h>
+#include <linux/reset.h>
+
+#include <asm/irq.h>
+
+#define to_amba_driver(d)	container_of(d, struct amba_driver, drv)
+
+/* called on periphid match and class 0x9 coresight device. */
+static int
+amba_cs_uci_id_match(const struct amba_id *table, struct amba_device *dev)
+{
+	int ret = 0;
+	struct amba_cs_uci_id *uci;
+
+	uci = table->data;
+
+	/* no table data or zero mask - return match on periphid */
+	if (!uci || (uci->devarch_mask == 0))
+		return 1;
+
+	/* test against read devtype and masked devarch value */
+	ret = (dev->uci.devtype == uci->devtype) &&
+		((dev->uci.devarch & uci->devarch_mask) == uci->devarch);
+	return ret;
+}
+
+static const struct amba_id *
+amba_lookup(const struct amba_id *table, struct amba_device *dev)
+{
+	while (table->mask) {
+		if (((dev->periphid & table->mask) == table->id) &&
+			((dev->cid != CORESIGHT_CID) ||
+			 (amba_cs_uci_id_match(table, dev))))
+			return table;
+		table++;
+	}
+	return NULL;
+}
+
+static int amba_match(struct device *dev, struct device_driver *drv)
+{
+	struct amba_device *pcdev = to_amba_device(dev);
+	struct amba_driver *pcdrv = to_amba_driver(drv);
+
+	/* When driver_override is set, only bind to the matching driver */
+	if (pcdev->driver_override)
+		return !strcmp(pcdev->driver_override, drv->name);
+
+	return amba_lookup(pcdrv->id_table, pcdev) != NULL;
+}
+
+static int amba_uevent(struct device *dev, struct kobj_uevent_env *env)
+{
+	struct amba_device *pcdev = to_amba_device(dev);
+	int retval = 0;
+
+	retval = add_uevent_var(env, "AMBA_ID=%08x", pcdev->periphid);
+	if (retval)
+		return retval;
+
+	retval = add_uevent_var(env, "MODALIAS=amba:d%08X", pcdev->periphid);
+	return retval;
+}
+
+static ssize_t driver_override_show(struct device *_dev,
+				    struct device_attribute *attr, char *buf)
+{
+	struct amba_device *dev = to_amba_device(_dev);
+	ssize_t len;
+
+	device_lock(_dev);
+	len = sprintf(buf, "%s\n", dev->driver_override);
+	device_unlock(_dev);
+	return len;
+}
+
+static ssize_t driver_override_store(struct device *_dev,
+				     struct device_attribute *attr,
+				     const char *buf, size_t count)
+{
+	struct amba_device *dev = to_amba_device(_dev);
+	char *driver_override, *old, *cp;
+
+	/* We need to keep extra room for a newline */
+	if (count >= (PAGE_SIZE - 1))
+		return -EINVAL;
+
+	driver_override = kstrndup(buf, count, GFP_KERNEL);
+	if (!driver_override)
+		return -ENOMEM;
+
+	cp = strchr(driver_override, '\n');
+	if (cp)
+		*cp = '\0';
+
+	device_lock(_dev);
+	old = dev->driver_override;
+	if (strlen(driver_override)) {
+		dev->driver_override = driver_override;
+	} else {
+		kfree(driver_override);
+		dev->driver_override = NULL;
+	}
+	device_unlock(_dev);
+
+	kfree(old);
+
+	return count;
+}
+static DEVICE_ATTR_RW(driver_override);
+
+#define amba_attr_func(name,fmt,arg...)					\
+static ssize_t name##_show(struct device *_dev,				\
+			   struct device_attribute *attr, char *buf)	\
+{									\
+	struct amba_device *dev = to_amba_device(_dev);			\
+	return sprintf(buf, fmt, arg);					\
+}									\
+static DEVICE_ATTR_RO(name)
+
+amba_attr_func(id, "%08x\n", dev->periphid);
+amba_attr_func(irq0, "%u\n", dev->irq[0]);
+amba_attr_func(irq1, "%u\n", dev->irq[1]);
+amba_attr_func(resource, "\t%016llx\t%016llx\t%016lx\n",
+	 (unsigned long long)dev->res.start, (unsigned long long)dev->res.end,
+	 dev->res.flags);
+
+static struct attribute *amba_dev_attrs[] = {
+	&dev_attr_id.attr,
+	&dev_attr_resource.attr,
+	&dev_attr_driver_override.attr,
+	NULL,
+};
+ATTRIBUTE_GROUPS(amba_dev);
+
+#ifdef CONFIG_PM
+/*
+ * Hooks to provide runtime PM of the pclk (bus clock).  It is safe to
+ * enable/disable the bus clock at runtime PM suspend/resume as this
+ * does not result in loss of context.
+ */
+static int amba_pm_runtime_suspend(struct device *dev)
+{
+	struct amba_device *pcdev = to_amba_device(dev);
+	int ret = pm_generic_runtime_suspend(dev);
+
+	if (ret == 0 && dev->driver) {
+		if (pm_runtime_is_irq_safe(dev))
+			clk_disable(pcdev->pclk);
+		else
+			clk_disable_unprepare(pcdev->pclk);
+	}
+
+	return ret;
+}
+
+static int amba_pm_runtime_resume(struct device *dev)
+{
+	struct amba_device *pcdev = to_amba_device(dev);
+	int ret;
+
+	if (dev->driver) {
+		if (pm_runtime_is_irq_safe(dev))
+			ret = clk_enable(pcdev->pclk);
+		else
+			ret = clk_prepare_enable(pcdev->pclk);
+		/* Failure is probably fatal to the system, but... */
+		if (ret)
+			return ret;
+	}
+
+	return pm_generic_runtime_resume(dev);
+}
+#endif /* CONFIG_PM */
+
+static const struct dev_pm_ops amba_pm = {
+	.suspend	= pm_generic_suspend,
+	.resume		= pm_generic_resume,
+	.freeze		= pm_generic_freeze,
+	.thaw		= pm_generic_thaw,
+	.poweroff	= pm_generic_poweroff,
+	.restore	= pm_generic_restore,
+	SET_RUNTIME_PM_OPS(
+		amba_pm_runtime_suspend,
+		amba_pm_runtime_resume,
+		NULL
+	)
+};
+
+/*
+ * Primecells are part of the Advanced Microcontroller Bus Architecture,
+ * so we call the bus "amba".
+ * DMA configuration for platform and AMBA bus is same. So here we reuse
+ * platform's DMA config routine.
+ */
+struct bus_type amba_bustype = {
+	.name		= "amba",
+	.dev_groups	= amba_dev_groups,
+	.match		= amba_match,
+	.uevent		= amba_uevent,
+	.dma_configure	= platform_dma_configure,
+	.pm		= &amba_pm,
+};
+EXPORT_SYMBOL_GPL(amba_bustype);
+
+static int __init amba_init(void)
+{
+	return bus_register(&amba_bustype);
+}
+
+postcore_initcall(amba_init);
+
+static int amba_get_enable_pclk(struct amba_device *pcdev)
+{
+	int ret;
+
+	pcdev->pclk = clk_get(&pcdev->dev, "apb_pclk");
+	if (IS_ERR(pcdev->pclk))
+		return PTR_ERR(pcdev->pclk);
+
+	ret = clk_prepare_enable(pcdev->pclk);
+	if (ret)
+		clk_put(pcdev->pclk);
+
+	return ret;
+}
+
+static void amba_put_disable_pclk(struct amba_device *pcdev)
+{
+	clk_disable_unprepare(pcdev->pclk);
+	clk_put(pcdev->pclk);
+}
+
+/*
+ * These are the device model conversion veneers; they convert the
+ * device model structures to our more specific structures.
+ */
+static int amba_probe(struct device *dev)
+{
+	struct amba_device *pcdev = to_amba_device(dev);
+	struct amba_driver *pcdrv = to_amba_driver(dev->driver);
+	const struct amba_id *id = amba_lookup(pcdrv->id_table, pcdev);
+	int ret;
+
+	do {
+		ret = of_clk_set_defaults(dev->of_node, false);
+		if (ret < 0)
+			break;
+
+		ret = dev_pm_domain_attach(dev, true);
+		if (ret)
+			break;
+
+		ret = amba_get_enable_pclk(pcdev);
+		if (ret) {
+			dev_pm_domain_detach(dev, true);
+			break;
+		}
+
+		pm_runtime_get_noresume(dev);
+		pm_runtime_set_active(dev);
+		pm_runtime_enable(dev);
+
+		ret = pcdrv->probe(pcdev, id);
+		if (ret == 0)
+			break;
+
+		pm_runtime_disable(dev);
+		pm_runtime_set_suspended(dev);
+		pm_runtime_put_noidle(dev);
+
+		amba_put_disable_pclk(pcdev);
+		dev_pm_domain_detach(dev, true);
+	} while (0);
+
+	return ret;
+}
+
+static int amba_remove(struct device *dev)
+{
+	struct amba_device *pcdev = to_amba_device(dev);
+	struct amba_driver *drv = to_amba_driver(dev->driver);
+
+	pm_runtime_get_sync(dev);
+	if (drv->remove)
+		drv->remove(pcdev);
+	pm_runtime_put_noidle(dev);
+
+	/* Undo the runtime PM settings in amba_probe() */
+	pm_runtime_disable(dev);
+	pm_runtime_set_suspended(dev);
+	pm_runtime_put_noidle(dev);
+
+	amba_put_disable_pclk(pcdev);
+	dev_pm_domain_detach(dev, true);
+
+	return 0;
+}
+
+static void amba_shutdown(struct device *dev)
+{
+	struct amba_driver *drv = to_amba_driver(dev->driver);
+
+	if (drv->shutdown)
+		drv->shutdown(to_amba_device(dev));
+}
+
+/**
+ *	amba_driver_register - register an AMBA device driver
+ *	@drv: amba device driver structure
+ *
+ *	Register an AMBA device driver with the Linux device model
+ *	core.  If devices pre-exist, the drivers probe function will
+ *	be called.
+ */
+int amba_driver_register(struct amba_driver *drv)
+{
+	if (!drv->probe)
+		return -EINVAL;
+
+	drv->drv.bus = &amba_bustype;
+	drv->drv.probe = amba_probe;
+	drv->drv.remove = amba_remove;
+	drv->drv.shutdown = amba_shutdown;
+
+	return driver_register(&drv->drv);
+}
+
+/**
+ *	amba_driver_unregister - remove an AMBA device driver
+ *	@drv: AMBA device driver structure to remove
+ *
+ *	Unregister an AMBA device driver from the Linux device
+ *	model.  The device model will call the drivers remove function
+ *	for each device the device driver is currently handling.
+ */
+void amba_driver_unregister(struct amba_driver *drv)
+{
+	driver_unregister(&drv->drv);
+}
+
+
+static void amba_device_release(struct device *dev)
+{
+	struct amba_device *d = to_amba_device(dev);
+
+	of_node_put(d->dev.of_node);
+	if (d->res.parent)
+		release_resource(&d->res);
+	kfree(d);
+}
+
+static int amba_device_try_add(struct amba_device *dev, struct resource *parent)
+{
+	u32 size;
+	void __iomem *tmp;
+	int i, ret;
+
+	ret = request_resource(parent, &dev->res);
+	if (ret)
+		goto err_out;
+
+	/* Hard-coded primecell ID instead of plug-n-play */
+	if (dev->periphid != 0)
+		goto skip_probe;
+
+	/*
+	 * Dynamically calculate the size of the resource
+	 * and use this for iomap
+	 */
+	size = resource_size(&dev->res);
+	tmp = ioremap(dev->res.start, size);
+	if (!tmp) {
+		ret = -ENOMEM;
+		goto err_release;
+	}
+
+	ret = dev_pm_domain_attach(&dev->dev, true);
+	if (ret) {
+		iounmap(tmp);
+		goto err_release;
+	}
+
+	ret = amba_get_enable_pclk(dev);
+	if (ret == 0) {
+		u32 pid, cid;
+		struct reset_control *rstc;
+
+		/*
+		 * Find reset control(s) of the amba bus and de-assert them.
+		 */
+		rstc = of_reset_control_array_get_optional_shared(dev->dev.of_node);
+		if (IS_ERR(rstc)) {
+			ret = PTR_ERR(rstc);
+			if (ret != -EPROBE_DEFER)
+				dev_err(&dev->dev, "can't get reset: %d\n",
+					ret);
+			goto err_reset;
+		}
+		reset_control_deassert(rstc);
+		reset_control_put(rstc);
+
+		/*
+		 * Read pid and cid based on size of resource
+		 * they are located at end of region
+		 */
+		for (pid = 0, i = 0; i < 4; i++)
+			pid |= (readl(tmp + size - 0x20 + 4 * i) & 255) <<
+				(i * 8);
+		for (cid = 0, i = 0; i < 4; i++)
+			cid |= (readl(tmp + size - 0x10 + 4 * i) & 255) <<
+				(i * 8);
+
+		if (cid == CORESIGHT_CID) {
+			/* set the base to the start of the last 4k block */
+			void __iomem *csbase = tmp + size - 4096;
+
+			dev->uci.devarch =
+				readl(csbase + UCI_REG_DEVARCH_OFFSET);
+			dev->uci.devtype =
+				readl(csbase + UCI_REG_DEVTYPE_OFFSET) & 0xff;
+		}
+
+		amba_put_disable_pclk(dev);
+
+		if (cid == AMBA_CID || cid == CORESIGHT_CID) {
+			dev->periphid = pid;
+			dev->cid = cid;
+		}
+
+		if (!dev->periphid)
+			ret = -ENODEV;
+	}
+
+	iounmap(tmp);
+	dev_pm_domain_detach(&dev->dev, true);
+
+	if (ret)
+		goto err_release;
+
+ skip_probe:
+	ret = device_add(&dev->dev);
+	if (ret)
+		goto err_release;
+
+	if (dev->irq[0])
+		ret = device_create_file(&dev->dev, &dev_attr_irq0);
+	if (ret == 0 && dev->irq[1])
+		ret = device_create_file(&dev->dev, &dev_attr_irq1);
+	if (ret == 0)
+		return ret;
+
+	device_unregister(&dev->dev);
+
+ err_release:
+	release_resource(&dev->res);
+ err_out:
+	return ret;
+
+ err_reset:
+	amba_put_disable_pclk(dev);
+	iounmap(tmp);
+	dev_pm_domain_detach(&dev->dev, true);
+	goto err_release;
+}
+
+/*
+ * Registration of AMBA device require reading its pid and cid registers.
+ * To do this, the device must be turned on (if it is a part of power domain)
+ * and have clocks enabled. However in some cases those resources might not be
+ * yet available. Returning EPROBE_DEFER is not a solution in such case,
+ * because callers don't handle this special error code. Instead such devices
+ * are added to the special list and their registration is retried from
+ * periodic worker, until all resources are available and registration succeeds.
+ */
+struct deferred_device {
+	struct amba_device *dev;
+	struct resource *parent;
+	struct list_head node;
+};
+
+static LIST_HEAD(deferred_devices);
+static DEFINE_MUTEX(deferred_devices_lock);
+
+static void amba_deferred_retry_func(struct work_struct *dummy);
+static DECLARE_DELAYED_WORK(deferred_retry_work, amba_deferred_retry_func);
+
+#define DEFERRED_DEVICE_TIMEOUT (msecs_to_jiffies(5 * 1000))
+
+static int amba_deferred_retry(void)
+{
+	struct deferred_device *ddev, *tmp;
+
+	mutex_lock(&deferred_devices_lock);
+
+	list_for_each_entry_safe(ddev, tmp, &deferred_devices, node) {
+		int ret = amba_device_try_add(ddev->dev, ddev->parent);
+
+		if (ret == -EPROBE_DEFER)
+			continue;
+
+		list_del_init(&ddev->node);
+		kfree(ddev);
+	}
+
+	mutex_unlock(&deferred_devices_lock);
+
+	return 0;
+}
+late_initcall(amba_deferred_retry);
+
+static void amba_deferred_retry_func(struct work_struct *dummy)
+{
+	amba_deferred_retry();
+
+	if (!list_empty(&deferred_devices))
+		schedule_delayed_work(&deferred_retry_work,
+				      DEFERRED_DEVICE_TIMEOUT);
+}
+
+/**
+ *	amba_device_add - add a previously allocated AMBA device structure
+ *	@dev: AMBA device allocated by amba_device_alloc
+ *	@parent: resource parent for this devices resources
+ *
+ *	Claim the resource, and read the device cell ID if not already
+ *	initialized.  Register the AMBA device with the Linux device
+ *	manager.
+ */
+int amba_device_add(struct amba_device *dev, struct resource *parent)
+{
+	int ret = amba_device_try_add(dev, parent);
+
+	if (ret == -EPROBE_DEFER) {
+		struct deferred_device *ddev;
+
+		ddev = kmalloc(sizeof(*ddev), GFP_KERNEL);
+		if (!ddev)
+			return -ENOMEM;
+
+		ddev->dev = dev;
+		ddev->parent = parent;
+		ret = 0;
+
+		mutex_lock(&deferred_devices_lock);
+
+		if (list_empty(&deferred_devices))
+			schedule_delayed_work(&deferred_retry_work,
+					      DEFERRED_DEVICE_TIMEOUT);
+		list_add_tail(&ddev->node, &deferred_devices);
+
+		mutex_unlock(&deferred_devices_lock);
+	}
+	return ret;
+}
+EXPORT_SYMBOL_GPL(amba_device_add);
+
+static struct amba_device *
+amba_aphb_device_add(struct device *parent, const char *name,
+		     resource_size_t base, size_t size, int irq1, int irq2,
+		     void *pdata, unsigned int periphid, u64 dma_mask,
+		     struct resource *resbase)
+{
+	struct amba_device *dev;
+	int ret;
+
+	dev = amba_device_alloc(name, base, size);
+	if (!dev)
+		return ERR_PTR(-ENOMEM);
+
+	dev->dev.coherent_dma_mask = dma_mask;
+	dev->irq[0] = irq1;
+	dev->irq[1] = irq2;
+	dev->periphid = periphid;
+	dev->dev.platform_data = pdata;
+	dev->dev.parent = parent;
+
+	ret = amba_device_add(dev, resbase);
+	if (ret) {
+		amba_device_put(dev);
+		return ERR_PTR(ret);
+	}
+
+	return dev;
+}
+
+struct amba_device *
+amba_apb_device_add(struct device *parent, const char *name,
+		    resource_size_t base, size_t size, int irq1, int irq2,
+		    void *pdata, unsigned int periphid)
+{
+	return amba_aphb_device_add(parent, name, base, size, irq1, irq2, pdata,
+				    periphid, 0, &iomem_resource);
+}
+EXPORT_SYMBOL_GPL(amba_apb_device_add);
+
+struct amba_device *
+amba_ahb_device_add(struct device *parent, const char *name,
+		    resource_size_t base, size_t size, int irq1, int irq2,
+		    void *pdata, unsigned int periphid)
+{
+	return amba_aphb_device_add(parent, name, base, size, irq1, irq2, pdata,
+				    periphid, ~0ULL, &iomem_resource);
+}
+EXPORT_SYMBOL_GPL(amba_ahb_device_add);
+
+struct amba_device *
+amba_apb_device_add_res(struct device *parent, const char *name,
+			resource_size_t base, size_t size, int irq1,
+			int irq2, void *pdata, unsigned int periphid,
+			struct resource *resbase)
+{
+	return amba_aphb_device_add(parent, name, base, size, irq1, irq2, pdata,
+				    periphid, 0, resbase);
+}
+EXPORT_SYMBOL_GPL(amba_apb_device_add_res);
+
+struct amba_device *
+amba_ahb_device_add_res(struct device *parent, const char *name,
+			resource_size_t base, size_t size, int irq1,
+			int irq2, void *pdata, unsigned int periphid,
+			struct resource *resbase)
+{
+	return amba_aphb_device_add(parent, name, base, size, irq1, irq2, pdata,
+				    periphid, ~0ULL, resbase);
+}
+EXPORT_SYMBOL_GPL(amba_ahb_device_add_res);
+
+
+static void amba_device_initialize(struct amba_device *dev, const char *name)
+{
+	device_initialize(&dev->dev);
+	if (name)
+		dev_set_name(&dev->dev, "%s", name);
+	dev->dev.release = amba_device_release;
+	dev->dev.bus = &amba_bustype;
+	dev->dev.dma_mask = &dev->dev.coherent_dma_mask;
+	dev->dev.dma_parms = &dev->dma_parms;
+	dev->res.name = dev_name(&dev->dev);
+}
+
+/**
+ *	amba_device_alloc - allocate an AMBA device
+ *	@name: sysfs name of the AMBA device
+ *	@base: base of AMBA device
+ *	@size: size of AMBA device
+ *
+ *	Allocate and initialize an AMBA device structure.  Returns %NULL
+ *	on failure.
+ */
+struct amba_device *amba_device_alloc(const char *name, resource_size_t base,
+	size_t size)
+{
+	struct amba_device *dev;
+
+	dev = kzalloc(sizeof(*dev), GFP_KERNEL);
+	if (dev) {
+		amba_device_initialize(dev, name);
+		dev->res.start = base;
+		dev->res.end = base + size - 1;
+		dev->res.flags = IORESOURCE_MEM;
+	}
+
+	return dev;
+}
+EXPORT_SYMBOL_GPL(amba_device_alloc);
+
+/**
+ *	amba_device_register - register an AMBA device
+ *	@dev: AMBA device to register
+ *	@parent: parent memory resource
+ *
+ *	Setup the AMBA device, reading the cell ID if present.
+ *	Claim the resource, and register the AMBA device with
+ *	the Linux device manager.
+ */
+int amba_device_register(struct amba_device *dev, struct resource *parent)
+{
+	amba_device_initialize(dev, dev->dev.init_name);
+	dev->dev.init_name = NULL;
+
+	return amba_device_add(dev, parent);
+}
+
+/**
+ *	amba_device_put - put an AMBA device
+ *	@dev: AMBA device to put
+ */
+void amba_device_put(struct amba_device *dev)
+{
+	put_device(&dev->dev);
+}
+EXPORT_SYMBOL_GPL(amba_device_put);
+
+/**
+ *	amba_device_unregister - unregister an AMBA device
+ *	@dev: AMBA device to remove
+ *
+ *	Remove the specified AMBA device from the Linux device
+ *	manager.  All files associated with this object will be
+ *	destroyed, and device drivers notified that the device has
+ *	been removed.  The AMBA device's resources including
+ *	the amba_device structure will be freed once all
+ *	references to it have been dropped.
+ */
+void amba_device_unregister(struct amba_device *dev)
+{
+	device_unregister(&dev->dev);
+}
+
+
+struct find_data {
+	struct amba_device *dev;
+	struct device *parent;
+	const char *busid;
+	unsigned int id;
+	unsigned int mask;
+};
+
+static int amba_find_match(struct device *dev, void *data)
+{
+	struct find_data *d = data;
+	struct amba_device *pcdev = to_amba_device(dev);
+	int r;
+
+	r = (pcdev->periphid & d->mask) == d->id;
+	if (d->parent)
+		r &= d->parent == dev->parent;
+	if (d->busid)
+		r &= strcmp(dev_name(dev), d->busid) == 0;
+
+	if (r) {
+		get_device(dev);
+		d->dev = pcdev;
+	}
+
+	return r;
+}
+
+/**
+ *	amba_find_device - locate an AMBA device given a bus id
+ *	@busid: bus id for device (or NULL)
+ *	@parent: parent device (or NULL)
+ *	@id: peripheral ID (or 0)
+ *	@mask: peripheral ID mask (or 0)
+ *
+ *	Return the AMBA device corresponding to the supplied parameters.
+ *	If no device matches, returns NULL.
+ *
+ *	NOTE: When a valid device is found, its refcount is
+ *	incremented, and must be decremented before the returned
+ *	reference.
+ */
+struct amba_device *
+amba_find_device(const char *busid, struct device *parent, unsigned int id,
+		 unsigned int mask)
+{
+	struct find_data data;
+
+	data.dev = NULL;
+	data.parent = parent;
+	data.busid = busid;
+	data.id = id;
+	data.mask = mask;
+
+	bus_for_each_dev(&amba_bustype, NULL, &data, amba_find_match);
+
+	return data.dev;
+}
+
+/**
+ *	amba_request_regions - request all mem regions associated with device
+ *	@dev: amba_device structure for device
+ *	@name: name, or NULL to use driver name
+ */
+int amba_request_regions(struct amba_device *dev, const char *name)
+{
+	int ret = 0;
+	u32 size;
+
+	if (!name)
+		name = dev->dev.driver->name;
+
+	size = resource_size(&dev->res);
+
+	if (!request_mem_region(dev->res.start, size, name))
+		ret = -EBUSY;
+
+	return ret;
+}
+
+/**
+ *	amba_release_regions - release mem regions associated with device
+ *	@dev: amba_device structure for device
+ *
+ *	Release regions claimed by a successful call to amba_request_regions.
+ */
+void amba_release_regions(struct amba_device *dev)
+{
+	u32 size;
+
+	size = resource_size(&dev->res);
+	release_mem_region(dev->res.start, size);
+}
+
+EXPORT_SYMBOL(amba_driver_register);
+EXPORT_SYMBOL(amba_driver_unregister);
+EXPORT_SYMBOL(amba_device_register);
+EXPORT_SYMBOL(amba_device_unregister);
+EXPORT_SYMBOL(amba_find_device);
+EXPORT_SYMBOL(amba_request_regions);
+EXPORT_SYMBOL(amba_release_regions);