branch Attitude Adjustment

git-svn-id: svn://svn.openwrt.org/openwrt/branches/attitude_adjustment@33625 3c298f89-4303-0410-b956-a3cf2f4a3e73

1 files changed, 768 insertions, 0 deletions

diff --git a/target/linux/s3c24xx/files-2.6.30/drivers/ar6000/hif/hif2.c b/target/linux/s3c24xx/files-2.6.30/drivers/ar6000/hif/hif2.c
new file mode 100644
index 000000000..386d96e66
--- /dev/null
+++ b/target/linux/s3c24xx/files-2.6.30/drivers/ar6000/hif/hif2.c
@@ -0,0 +1,768 @@
+/*
+ * hif2.c - HIF layer re-implementation for the Linux SDIO stack
+ *
+ * Copyright (C) 2008, 2009 by OpenMoko, Inc.
+ * Written by Werner Almesberger <werner@openmoko.org>
+ * All Rights Reserved
+ *
+ * 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;
+ *
+ * Based on:
+ *
+ * @abstract: HIF layer reference implementation for Atheros SDIO stack
+ * @notice: Copyright (c) 2004-2006 Atheros Communications Inc.
+ */
+
+
+#include <linux/kernel.h>
+#include <linux/kthread.h>
+#include <linux/list.h>
+#include <linux/wait.h>
+#include <linux/spinlock.h>
+#include <linux/mutex.h>
+#include <linux/sched.h>
+#include <linux/mmc/sdio_func.h>
+#include <linux/mmc/sdio.h>
+#include <linux/mmc/sdio_ids.h>
+
+#include "athdefs.h"
+#include "a_types.h"
+#include "hif.h"
+
+
+/* @@@ Hack - this wants cleaning up */
+
+#ifdef CONFIG_MACH_NEO1973_GTA02
+
+#include <mach/gta02-pm-wlan.h>
+
+#else /* CONFIG_MACH_NEO1973_GTA02 */
+
+#define	gta02_wlan_query_rfkill_lock()  1
+#define	gta02_wlan_set_rfkill_cb(cb, hif) ((void) cb)
+#define	gta02_wlan_query_rfkill_unlock()
+#define	gta02_wlan_clear_rfkill_cb()
+
+#endif /* !CONFIG_MACH_NEO1973_GTA02 */
+
+
+/*
+ * KNOWN BUGS:
+ *
+ * - HIF_DEVICE_IRQ_ASYNC_SYNC doesn't work yet (gets MMC errors)
+ * - latency can reach hundreds of ms, probably because of scheduling delays
+ * - packets go through about three queues before finally hitting the network
+ */
+
+/*
+ * Differences from Atheros' HIFs:
+ *
+ * - synchronous and asynchronous requests may get reordered with respect to
+ *   each other, e.g., if HIFReadWrite returns for an asynchronous request and
+ *   then HIFReadWrite is called for a synchronous request, the synchronous
+ *   request may be executed before the asynchronous request.
+ *
+ * - request queue locking seems unnecessarily complex in the Atheros HIFs.
+ *
+ * - Atheros mask interrupts by calling sdio_claim_irq/sdio_release_irq, which
+ *   can cause quite a bit of overhead. This HIF has its own light-weight
+ *   interrupt masking.
+ *
+ * - Atheros call deviceInsertedHandler from a thread spawned off the probe or
+ *   device insertion function. The original explanation for the Atheros SDIO
+ *   stack said that this is done because a delay is needed to let the chip
+ *   complete initialization. There is indeed a one second delay in the thread.
+ *
+ *   The Atheros Linux SDIO HIF removes the delay and only retains the thread.
+ *   Experimentally removing the thread didn't show any conflicts, so let's get
+ *   rid of it for good.
+ *
+ * - The Atheros SDIO stack with Samuel's driver sets SDIO_CCCR_POWER in
+ *   SDIO_POWER_EMPC. Atheros' Linux SDIO code apparently doesn't. We don't
+ *   either, and this seems to work fine.
+ *   @@@ Need to check this with Atheros.
+ */
+
+
+#define MBOXES			4
+
+#define HIF_MBOX_BLOCK_SIZE	128
+#define	HIF_MBOX_BASE_ADDR	0x800
+#define	HIF_MBOX_WIDTH		0x800
+#define	HIF_MBOX_START_ADDR(mbox) \
+    (HIF_MBOX_BASE_ADDR+(mbox)*HIF_MBOX_WIDTH)
+
+
+struct hif_device {
+	void *htc_handle;
+	struct sdio_func *func;
+
+	/*
+	 * @@@ our sweet little bit of bogosity - the mechanism that lets us
+	 * use the SDIO stack from softirqs. This really wants to use skbs.
+	 */
+	struct list_head queue;
+	spinlock_t queue_lock;
+	struct task_struct *io_task;
+	wait_queue_head_t wait;
+
+	/*
+	 * activate_lock protects "active" and the activation/deactivation
+	 * process itself.
+	 *
+	 * Relation to other locks: The SDIO function can be claimed while
+	 * activate_lock is being held, but trying to acquire activate_lock
+	 * while having ownership of the SDIO function could cause a deadlock.
+	 */
+	int active;
+	struct mutex activate_lock;
+};
+
+struct hif_request {
+	struct list_head list;
+	struct sdio_func *func;
+	int (*read)(struct sdio_func *func,
+	    void *dst, unsigned int addr, int count);
+	int (*write)(struct sdio_func *func,
+	    unsigned int addr, void *src, int count);
+	void *buf;
+	unsigned long addr;
+	int len;
+	A_STATUS (*completion)(void *context, A_STATUS status);
+	void *context;
+};
+
+
+static HTC_CALLBACKS htcCallbacks;
+
+/*
+ * shutdown_lock prevents recursion through HIFShutDownDevice
+ */
+static DEFINE_MUTEX(shutdown_lock);
+
+
+/* ----- Request processing ------------------------------------------------ */
+
+
+static A_STATUS process_request(struct hif_request *req)
+{
+	int ret;
+	A_STATUS status;
+
+	dev_dbg(&req->func->dev, "process_request(req %p)\n", req);
+	sdio_claim_host(req->func);
+	if (req->read) {
+		ret = req->read(req->func, req->buf, req->addr, req->len);
+	} else {
+		ret = req->write(req->func, req->addr, req->buf, req->len);
+	}
+	sdio_release_host(req->func);
+	status = ret ? A_ERROR : A_OK;
+	if (req->completion)
+		req->completion(req->context, status);
+	kfree(req);
+	return status;
+}
+
+
+static void enqueue_request(struct hif_device *hif, struct hif_request *req)
+{
+	unsigned long flags;
+
+	dev_dbg(&req->func->dev, "enqueue_request(req %p)\n", req);
+	spin_lock_irqsave(&hif->queue_lock, flags);
+	list_add_tail(&req->list, &hif->queue);
+	spin_unlock_irqrestore(&hif->queue_lock, flags);
+	wake_up(&hif->wait);
+}
+
+
+static struct hif_request *dequeue_request(struct hif_device *hif)
+{
+	struct hif_request *req;
+	unsigned long flags;
+
+	spin_lock_irqsave(&hif->queue_lock, flags);
+	if (list_empty(&hif->queue))
+		req = NULL;
+	else {
+		req = list_first_entry(&hif->queue,
+		    struct hif_request, list);
+		list_del(&req->list);
+	}
+	spin_unlock_irqrestore(&hif->queue_lock, flags);
+	return req;
+}
+
+
+static void wait_queue_empty(struct hif_device *hif)
+{
+	unsigned long flags;
+	int empty;
+
+	while (1) {
+		spin_lock_irqsave(&hif->queue_lock, flags);
+		empty = list_empty(&hif->queue);
+		spin_unlock_irqrestore(&hif->queue_lock, flags);
+		if (empty)
+			break;
+		else
+			yield();
+	}
+}
+
+
+static int io(void *data)
+{
+	struct hif_device *hif = data;
+	struct sched_param param = { .sched_priority = 2 };
+		/* one priority level slower than ksdioirqd (which is at 1) */
+	DEFINE_WAIT(wait);
+	struct hif_request *req;
+
+	sched_setscheduler(current, SCHED_FIFO, &param);
+
+	while (1) {
+		while (1) {
+			/*
+			 * Since we never use signals here, one might think
+			 * that this ought to be TASK_UNINTERRUPTIBLE. However,
+			 * such a task would increase the load average and,
+			 * worse, it would trigger the softlockup check.
+			 */
+			prepare_to_wait(&hif->wait, &wait, TASK_INTERRUPTIBLE);
+			if (kthread_should_stop()) {
+				finish_wait(&hif->wait, &wait);
+				return 0;
+			}
+			req = dequeue_request(hif);
+			if (req)
+				break;
+			schedule();
+		}
+		finish_wait(&hif->wait, &wait);
+
+		(void) process_request(req);
+	}
+	return 0;
+}
+
+
+A_STATUS HIFReadWrite(HIF_DEVICE *hif, A_UINT32 address, A_UCHAR *buffer,
+    A_UINT32 length, A_UINT32 request, void *context)
+{
+	struct device *dev = HIFGetOSDevice(hif);
+	struct hif_request *req;
+
+	dev_dbg(dev, "HIFReadWrite(device %p, address 0x%x, buffer %p, "
+	    "length %d, request 0x%x, context %p)\n",
+	    hif, address, buffer, length, request, context);
+
+	BUG_ON(!(request & (HIF_SYNCHRONOUS | HIF_ASYNCHRONOUS)));
+	BUG_ON(!(request & (HIF_BYTE_BASIS | HIF_BLOCK_BASIS)));
+	BUG_ON(!(request & (HIF_READ | HIF_WRITE)));
+	BUG_ON(!(request & HIF_EXTENDED_IO));
+
+	if (address >= HIF_MBOX_START_ADDR(0) &&
+	    address < HIF_MBOX_START_ADDR(MBOXES+1)) {
+		BUG_ON(length > HIF_MBOX_WIDTH);
+		/* Adjust the address so that the last byte falls on the EOM
+		   address. */
+		address += HIF_MBOX_WIDTH-length;
+	}
+
+	req = kzalloc(sizeof(*req), GFP_ATOMIC);
+	if (!req) {
+		if (request & HIF_ASYNCHRONOUS)
+			htcCallbacks.rwCompletionHandler(context, A_ERROR);
+		return A_ERROR;
+	}
+
+	req->func = hif->func;
+	req->addr = address;
+	req->buf = buffer;
+	req->len = length;
+
+	if (request & HIF_READ) {
+		if (request & HIF_FIXED_ADDRESS)
+			req->read = sdio_readsb;
+		else
+			req->read = sdio_memcpy_fromio;
+	} else {
+		if (request & HIF_FIXED_ADDRESS)
+			req->write = sdio_writesb;
+		else
+			req->write = sdio_memcpy_toio;
+	}
+
+	if (!(request & HIF_ASYNCHRONOUS))
+		return process_request(req);
+
+	req->completion = htcCallbacks.rwCompletionHandler;
+	req->context = context;
+	enqueue_request(hif, req);
+
+	return A_OK;
+}
+
+
+/* ----- Interrupt handling ------------------------------------------------ */
+
+/*
+ * Volatile ought to be good enough to make gcc do the right thing on S3C24xx.
+ * No need to use atomic or put barriers, keeping the code more readable.
+ *
+ * Warning: this story changes if going SMP/SMT.
+ */
+
+static volatile int masked = 1;
+static volatile int pending;
+static volatile int in_interrupt;
+
+
+static void ar6000_do_irq(struct sdio_func *func)
+{
+	HIF_DEVICE *hif = sdio_get_drvdata(func);
+	struct device *dev = HIFGetOSDevice(hif);
+	A_STATUS status;
+
+	dev_dbg(dev, "ar6000_do_irq -> %p\n", htcCallbacks.dsrHandler);
+
+	status = htcCallbacks.dsrHandler(hif->htc_handle);
+	BUG_ON(status != A_OK);
+}
+
+
+static void sdio_ar6000_irq(struct sdio_func *func)
+{
+	HIF_DEVICE *hif = sdio_get_drvdata(func);
+	struct device *dev = HIFGetOSDevice(hif);
+
+	dev_dbg(dev, "sdio_ar6000_irq\n");
+
+	in_interrupt = 1;
+	if (masked) {
+		in_interrupt = 0;
+		pending++;
+		return;
+	}
+	/*
+	 * @@@ This is ugly. If we don't drop the lock, we'll deadlock when
+	 * the handler tries to do SDIO. So there are four choices:
+	 *
+	 * 1) Break the call chain by calling the callback from a workqueue.
+	 *    Ugh.
+	 * 2) Make process_request aware that we already have the lock.
+	 * 3) Drop the lock. Which is ugly but should be safe as long as we're
+	 *    making sure the device doesn't go away.
+	 * 4) Change the AR6k driver such that it only issues asynchronous
+	 *    quests when called from an interrupt.
+	 *
+	 * Solution 2) is probably the best for now. Will try it later.
+	 */
+	sdio_release_host(func);
+	ar6000_do_irq(func);
+	sdio_claim_host(func);
+	in_interrupt = 0;
+}
+
+
+void HIFAckInterrupt(HIF_DEVICE *hif)
+{
+	struct device *dev = HIFGetOSDevice(hif);
+
+	dev_dbg(dev, "HIFAckInterrupt\n");
+	/* do nothing */
+}
+
+
+void HIFUnMaskInterrupt(HIF_DEVICE *hif)
+{
+	struct device *dev = HIFGetOSDevice(hif);
+
+	dev_dbg(dev, "HIFUnMaskInterrupt\n");
+	do {
+		masked = 1;
+		if (pending) {
+			pending = 0;
+			ar6000_do_irq(hif->func);
+			/* We may take an interrupt before unmasking and thus
+			   get it pending. In this case, we just loop back. */
+		}
+		masked = 0;
+	}
+	while (pending);
+}
+
+
+void HIFMaskInterrupt(HIF_DEVICE *hif)
+{
+	struct device *dev = HIFGetOSDevice(hif);
+
+	dev_dbg(dev, "HIFMaskInterrupt\n");
+	/*
+	 * Since sdio_ar6000_irq can also be called from a process context, we
+	 * may conceivably end up racing with it. Thus, we need to wait until
+	 * we can be sure that no concurrent interrupt processing is going on
+	 * before we return.
+	 *
+	 * Note: this may be a bit on the paranoid side - the callers may
+	 * actually be nice enough to disable scheduling. Check later.
+	 */
+	masked = 1;
+	while (in_interrupt)
+		yield();
+}
+
+
+/* ----- HIF API glue functions -------------------------------------------- */
+
+
+struct device *HIFGetOSDevice(HIF_DEVICE *hif)
+{
+	return &hif->func->dev;
+}
+
+
+void HIFSetHandle(void *hif_handle, void *handle)
+{
+	HIF_DEVICE *hif = (HIF_DEVICE *) hif_handle;
+
+	hif->htc_handle = handle;
+}
+
+
+/* ----- Device configuration (HIF side) ----------------------------------- */
+
+
+A_STATUS HIFConfigureDevice(HIF_DEVICE *hif,
+    HIF_DEVICE_CONFIG_OPCODE opcode, void *config, A_UINT32 configLen)
+{
+	struct device *dev = HIFGetOSDevice(hif);
+	HIF_DEVICE_IRQ_PROCESSING_MODE *ipm_cfg = config;
+	A_UINT32 *mbs_cfg = config;
+	int i;
+
+	dev_dbg(dev, "HIFConfigureDevice\n");
+
+	switch (opcode) {
+	case HIF_DEVICE_GET_MBOX_BLOCK_SIZE:
+		for (i = 0; i != MBOXES; i++)
+			mbs_cfg[i] = HIF_MBOX_BLOCK_SIZE;
+		break;
+	case HIF_DEVICE_GET_MBOX_ADDR:
+		for (i = 0; i != MBOXES; i++)
+			mbs_cfg[i] = HIF_MBOX_START_ADDR(i);
+		break;
+	case HIF_DEVICE_GET_IRQ_PROC_MODE:
+		*ipm_cfg = HIF_DEVICE_IRQ_SYNC_ONLY;
+//		*ipm_cfg = HIF_DEVICE_IRQ_ASYNC_SYNC;
+		break;
+	default:
+		return A_ERROR;
+	}
+	return A_OK;
+}
+
+
+/* ----- Device probe and removal (Linux side) ----------------------------- */
+
+
+static int ar6000_do_activate(struct hif_device *hif)
+{
+	struct sdio_func *func = hif->func;
+	struct device *dev = &func->dev;
+	int ret;
+
+	dev_dbg(dev, "ar6000_do_activate\n");
+
+	sdio_claim_host(func);
+	sdio_enable_func(func);
+
+	INIT_LIST_HEAD(&hif->queue);
+	init_waitqueue_head(&hif->wait);
+	spin_lock_init(&hif->queue_lock);
+
+	ret = sdio_set_block_size(func, HIF_MBOX_BLOCK_SIZE);
+	if (ret < 0) {
+		dev_err(dev, "sdio_set_block_size returns %d\n", ret);
+		goto out_enabled;
+	}
+	ret = sdio_claim_irq(func, sdio_ar6000_irq);
+	if (ret) {
+		dev_err(dev, "sdio_claim_irq returns %d\n", ret);
+		goto out_enabled;
+	}
+	/* Set SDIO_BUS_CD_DISABLE in SDIO_CCCR_IF ? */
+#if 0
+	sdio_f0_writeb(func, SDIO_CCCR_CAP_E4MI, SDIO_CCCR_CAPS, &ret);
+	if (ret) {
+		dev_err(dev, "sdio_f0_writeb(SDIO_CCCR_CAPS) returns %d\n",
+		    ret);
+		goto out_got_irq;
+	}
+#else
+	if (0) /* avoid warning */
+		goto out_got_irq;
+#endif
+
+	sdio_release_host(func);
+
+	hif->io_task = kthread_run(io, hif, "ar6000_io");
+	ret = IS_ERR(hif->io_task);
+	if (ret) {
+		dev_err(dev, "kthread_run(ar6000_io): %d\n", ret);
+		goto out_func_ready;
+	}
+
+	ret = htcCallbacks.deviceInsertedHandler(hif);
+	if (ret == A_OK)
+		return 0;
+
+	dev_err(dev, "deviceInsertedHandler: %d\n", ret);
+
+	ret = kthread_stop(hif->io_task);
+	if (ret)
+		dev_err(dev, "kthread_stop (ar6000_io): %d\n", ret);
+
+out_func_ready:
+	sdio_claim_host(func);
+
+out_got_irq:
+	sdio_release_irq(func);
+
+out_enabled:
+	sdio_disable_func(func);
+	sdio_release_host(func);
+
+	return ret;
+}
+
+
+static void ar6000_do_deactivate(struct hif_device *hif)
+{
+	struct sdio_func *func = hif->func;
+	struct device *dev = &func->dev;
+	int ret;
+
+	dev_dbg(dev, "ar6000_do_deactivate\n");
+	if (!hif->active)
+		return;
+
+	if (mutex_trylock(&shutdown_lock)) {
+		/*
+		 * Funny, Atheros' HIF does this call, but this just puts us in
+		 * a recursion through HTCShutDown/HIFShutDown if unloading the
+		 * module.
+		 *
+		 * However, we need it for suspend/resume. See the comment at
+		 * HIFShutDown, below.
+		 */
+		ret = htcCallbacks.deviceRemovedHandler(hif->htc_handle, A_OK);
+		if (ret != A_OK)
+			dev_err(dev, "deviceRemovedHandler: %d\n", ret);
+		mutex_unlock(&shutdown_lock);
+	}
+	wait_queue_empty(hif);
+	ret = kthread_stop(hif->io_task);
+	if (ret)
+		dev_err(dev, "kthread_stop (ar6000_io): %d\n", ret);
+	sdio_claim_host(func);
+	sdio_release_irq(func);
+	sdio_disable_func(func);
+	sdio_release_host(func);
+}
+
+
+static int ar6000_activate(struct hif_device *hif)
+{
+	int ret = 0;
+
+	dev_dbg(&hif->func->dev, "ar6000_activate\n");
+	mutex_lock(&hif->activate_lock);
+	if (!hif->active) {
+		ret = ar6000_do_activate(hif);
+		if (ret) {
+			printk(KERN_ERR "%s: Failed to activate %d\n",
+				__func__, ret);
+			goto out;
+		}
+		hif->active = 1;
+	}
+out:
+	mutex_unlock(&hif->activate_lock);
+	return ret;
+}
+
+
+static void ar6000_deactivate(struct hif_device *hif)
+{
+	dev_dbg(&hif->func->dev, "ar6000_deactivate\n");
+	mutex_lock(&hif->activate_lock);
+	if (hif->active) {
+		ar6000_do_deactivate(hif);
+		hif->active = 0;
+	}
+	mutex_unlock(&hif->activate_lock);
+}
+
+
+static int ar6000_rfkill_cb(void *data, int on)
+{
+	struct hif_device *hif = data;
+	struct sdio_func *func = hif->func;
+	struct device *dev = &func->dev;
+
+	dev_dbg(dev, "ar6000_rfkill_cb: on %d\n", on);
+	if (on)
+		return ar6000_activate(hif);
+	ar6000_deactivate(hif);
+	return 0;
+}
+
+
+static int sdio_ar6000_probe(struct sdio_func *func,
+    const struct sdio_device_id *id)
+{
+	struct device *dev = &func->dev;
+	struct hif_device *hif;
+	int ret = 0;
+
+	dev_dbg(dev, "sdio_ar6000_probe\n");
+	BUG_ON(!htcCallbacks.deviceInsertedHandler);
+
+	hif = kzalloc(sizeof(*hif), GFP_KERNEL);
+	if (!hif)
+		return -ENOMEM;
+
+	sdio_set_drvdata(func, hif);
+	hif->func = func;
+	mutex_init(&hif->activate_lock);
+	hif->active = 0;
+
+	if (gta02_wlan_query_rfkill_lock())
+		ret = ar6000_activate(hif);
+	if (!ret) {
+		gta02_wlan_set_rfkill_cb(ar6000_rfkill_cb, hif);
+		return 0;
+	}
+	gta02_wlan_query_rfkill_unlock();
+	sdio_set_drvdata(func, NULL);
+	kfree(hif);
+	return ret;
+}
+
+
+static void sdio_ar6000_remove(struct sdio_func *func)
+{
+	struct device *dev = &func->dev;
+	HIF_DEVICE *hif = sdio_get_drvdata(func);
+
+	dev_dbg(dev, "sdio_ar6000_remove\n");
+	gta02_wlan_clear_rfkill_cb();
+	ar6000_deactivate(hif);
+	sdio_set_drvdata(func, NULL);
+	kfree(hif);
+}
+
+
+/* ----- Device registration/unregistration (called by HIF) ---------------- */
+
+
+#define ATHEROS_SDIO_DEVICE(id, offset) \
+    SDIO_DEVICE(SDIO_VENDOR_ID_ATHEROS, SDIO_DEVICE_ID_ATHEROS_##id | (offset))
+
+static const struct sdio_device_id sdio_ar6000_ids[] = {
+	{ ATHEROS_SDIO_DEVICE(AR6002, 0)	},
+	{ ATHEROS_SDIO_DEVICE(AR6002, 0x1)	},
+	{ ATHEROS_SDIO_DEVICE(AR6001, 0x8)	},
+	{ ATHEROS_SDIO_DEVICE(AR6001, 0x9)	},
+	{ ATHEROS_SDIO_DEVICE(AR6001, 0xa)	},
+	{ ATHEROS_SDIO_DEVICE(AR6001, 0xb)	},
+	{ /* end: all zeroes */			},
+};
+
+MODULE_DEVICE_TABLE(sdio, sdio_ar6000_ids);
+
+
+static struct sdio_driver sdio_ar6000_driver = {
+	.probe		= sdio_ar6000_probe,
+	.remove		= sdio_ar6000_remove,
+	.name		= "sdio_ar6000",
+	.id_table	= sdio_ar6000_ids,
+};
+
+
+int HIFInit(HTC_CALLBACKS *callbacks)
+{
+	int ret;
+
+	BUG_ON(!callbacks);
+
+	printk(KERN_DEBUG "HIFInit\n");
+	htcCallbacks = *callbacks;
+
+	ret = sdio_register_driver(&sdio_ar6000_driver);
+	if (ret) {
+		printk(KERN_ERR
+		    "sdio_register_driver(sdio_ar6000_driver): %d\n", ret);
+		return A_ERROR;
+	}
+
+	return 0;
+}
+
+
+/*
+ * We have four possible call chains here:
+ *
+ * System shutdown/reboot:
+ *
+ *   kernel_restart_prepare ...> device_shutdown ... > s3cmci_shutdown ->
+ *     mmc_remove_host ..> sdio_bus_remove -> sdio_ar6000_remove ->
+ *     ar6000_deactivate -> ar6000_do_deactivate ->
+ *     deviceRemovedHandler (HTCTargetRemovedHandler) -> HIFShutDownDevice
+ *
+ *   This is roughly the same sequence as suspend, described below.
+ *
+ * Module removal:
+ *
+ *   sys_delete_module -> ar6000_cleanup_module -> HTCShutDown ->
+ *     HIFShutDownDevice -> sdio_unregister_driver ...> sdio_bus_remove ->
+ *     sdio_ar6000_remove -> ar6000_deactivate -> ar6000_do_deactivate
+ *
+ *   In this case, HIFShutDownDevice must call sdio_unregister_driver to
+ *   notify the driver about its removal. ar6000_do_deactivate must not call
+ *   deviceRemovedHandler, because that would loop back into HIFShutDownDevice.
+ *
+ * Suspend:
+ *
+ *   device_suspend ...> s3cmci_suspend ...> sdio_bus_remove ->
+ *     sdio_ar6000_remove -> ar6000_deactivate -> ar6000_do_deactivate ->
+ *     deviceRemovedHandler (HTCTargetRemovedHandler) -> HIFShutDownDevice
+ *
+ *   We must call deviceRemovedHandler to inform the ar6k stack that the device
+ *   has been removed. Since HTCTargetRemovedHandler calls back into
+ *   HIFShutDownDevice, we must also prevent the call to
+ *   sdio_unregister_driver, or we'd end up recursing into the SDIO stack,
+ *   eventually deadlocking somewhere.
+ *
+ * rfkill:
+ *
+ *   rfkill_state_store -> rfkill_toggle_radio -> gta02_wlan_toggle_radio ->
+ *   ar6000_rfkill_cb -> ar6000_deactivate -> ar6000_do_deactivate ->
+ *     deviceRemovedHandler (HTCTargetRemovedHandler) -> HIFShutDownDevice
+ *
+ *   This is similar to suspend - only the entry point changes.
+ */
+
+void HIFShutDownDevice(HIF_DEVICE *hif)
+{
+	/* Beware, HTCShutDown calls us with hif == NULL ! */
+	if (mutex_trylock(&shutdown_lock)) {
+		sdio_unregister_driver(&sdio_ar6000_driver);
+		mutex_unlock(&shutdown_lock);
+	}
+}