drivers/misc/ioc4.c - maze/linux - Git at Google

 /*
  * This file is subject to the terms and conditions of the GNU General Public
  * License.  See the file "COPYING" in the main directory of this archive
  * for more details.
  *
  * Copyright (C) 2005-2006 Silicon Graphics, Inc.  All Rights Reserved.
  */

 /* This file contains the master driver module for use by SGI IOC4 subdrivers.
  *
  * It allocates any resources shared between multiple subdevices, and
  * provides accessor functions (where needed) and the like for those
  * resources.  It also provides a mechanism for the subdevice modules
  * to support loading and unloading.
  *
  * Non-shared resources (e.g. external interrupt A_INT_OUT register page
  * alias, serial port and UART registers) are handled by the subdevice
  * modules themselves.
  *
  * This is all necessary because IOC4 is not implemented as a multi-function
  * PCI device, but an amalgamation of disparate registers for several
  * types of device (ATA, serial, external interrupts).  The normal
  * resource management in the kernel doesn't have quite the right interfaces
  * to handle this situation (e.g. multiple modules can't claim the same
  * PCI ID), thus this IOC4 master module.
  */

 #include <linux/errno.h>
 #include <linux/module.h>
 #include <linux/pci.h>
 #include <linux/ioc4.h>
 #include <linux/ktime.h>
 #include <linux/slab.h>
 #include <linux/mutex.h>
 #include <linux/time.h>
 #include <asm/io.h>

 /***************
  * Definitions *
  ***************/

 /* Tweakable values */

 /* PCI bus speed detection/calibration */
 #define IOC4_CALIBRATE_COUNT 63		/* Calibration cycle period */
 #define IOC4_CALIBRATE_CYCLES 256	/* Average over this many cycles */
 #define IOC4_CALIBRATE_DISCARD 2	/* Discard first few cycles */
 #define IOC4_CALIBRATE_LOW_MHZ 25	/* Lower bound on bus speed sanity */
 #define IOC4_CALIBRATE_HIGH_MHZ 75	/* Upper bound on bus speed sanity */
 #define IOC4_CALIBRATE_DEFAULT_MHZ 66	/* Assumed if sanity check fails */

 /************************
  * Submodule management *
  ************************/

 static DEFINE_MUTEX(ioc4_mutex);

 static LIST_HEAD(ioc4_devices);
 static LIST_HEAD(ioc4_submodules);

 /* Register an IOC4 submodule */
 int
 ioc4_register_submodule(struct ioc4_submodule *is)
 {
 	struct ioc4_driver_data *idd;

 	mutex_lock(&ioc4_mutex);
 	list_add(&is->is_list, &ioc4_submodules);

 	/* Initialize submodule for each IOC4 */
 	if (!is->is_probe)
 		goto out;

 	list_for_each_entry(idd, &ioc4_devices, idd_list) {
 		if (is->is_probe(idd)) {
 			printk(KERN_WARNING
 			       "%s: IOC4 submodule %s probe failed "
 			       "for pci_dev %s",
 			       __func__, module_name(is->is_owner),
 			       pci_name(idd->idd_pdev));
 		}
 	}
  out:
 	mutex_unlock(&ioc4_mutex);
 	return 0;
 }

 /* Unregister an IOC4 submodule */
 void
 ioc4_unregister_submodule(struct ioc4_submodule *is)
 {
 	struct ioc4_driver_data *idd;

 	mutex_lock(&ioc4_mutex);
 	list_del(&is->is_list);

 	/* Remove submodule for each IOC4 */
 	if (!is->is_remove)
 		goto out;

 	list_for_each_entry(idd, &ioc4_devices, idd_list) {
 		if (is->is_remove(idd)) {
 			printk(KERN_WARNING
 			       "%s: IOC4 submodule %s remove failed "
 			       "for pci_dev %s.\n",
 			       __func__, module_name(is->is_owner),
 			       pci_name(idd->idd_pdev));
 		}
 	}
  out:
 	mutex_unlock(&ioc4_mutex);
 }

 /*********************
  * Device management *
  *********************/

 #define IOC4_CALIBRATE_LOW_LIMIT \
 	(1000*IOC4_EXTINT_COUNT_DIVISOR/IOC4_CALIBRATE_LOW_MHZ)
 #define IOC4_CALIBRATE_HIGH_LIMIT \
 	(1000*IOC4_EXTINT_COUNT_DIVISOR/IOC4_CALIBRATE_HIGH_MHZ)
 #define IOC4_CALIBRATE_DEFAULT \
 	(1000*IOC4_EXTINT_COUNT_DIVISOR/IOC4_CALIBRATE_DEFAULT_MHZ)

 #define IOC4_CALIBRATE_END \
 	(IOC4_CALIBRATE_CYCLES + IOC4_CALIBRATE_DISCARD)

 #define IOC4_INT_OUT_MODE_TOGGLE 0x7	/* Toggle INT_OUT every COUNT+1 ticks */

 /* Determines external interrupt output clock period of the PCI bus an
  * IOC4 is attached to.  This value can be used to determine the PCI
  * bus speed.
  *
  * IOC4 has a design feature that various internal timers are derived from
  * the PCI bus clock.  This causes IOC4 device drivers to need to take the
  * bus speed into account when setting various register values (e.g. INT_OUT
  * register COUNT field, UART divisors, etc).  Since this information is
  * needed by several subdrivers, it is determined by the main IOC4 driver,
  * even though the following code utilizes external interrupt registers
  * to perform the speed calculation.
  */
 static void __devinit
 ioc4_clock_calibrate(struct ioc4_driver_data *idd)
 {
 	union ioc4_int_out int_out;
 	union ioc4_gpcr gpcr;
 	unsigned int state, last_state = 1;
 	struct timespec start_ts, end_ts;
 	uint64_t start, end, period;
 	unsigned int count = 0;

 	/* Enable output */
 	gpcr.raw = 0;
 	gpcr.fields.dir = IOC4_GPCR_DIR_0;
 	gpcr.fields.int_out_en = 1;
 	writel(gpcr.raw, &idd->idd_misc_regs->gpcr_s.raw);

 	/* Reset to power-on state */
 	writel(0, &idd->idd_misc_regs->int_out.raw);
 	mmiowb();

 	/* Set up square wave */
 	int_out.raw = 0;
 	int_out.fields.count = IOC4_CALIBRATE_COUNT;
 	int_out.fields.mode = IOC4_INT_OUT_MODE_TOGGLE;
 	int_out.fields.diag = 0;
 	writel(int_out.raw, &idd->idd_misc_regs->int_out.raw);
 	mmiowb();

 	/* Check square wave period averaged over some number of cycles */
 	do {
 		int_out.raw = readl(&idd->idd_misc_regs->int_out.raw);
 		state = int_out.fields.int_out;
 		if (!last_state && state) {
 			count++;
 			if (count == IOC4_CALIBRATE_END) {
 				ktime_get_ts(&end_ts);
 				break;
 			} else if (count == IOC4_CALIBRATE_DISCARD)
 				ktime_get_ts(&start_ts);
 		}
 		last_state = state;
 	} while (1);

 	/* Calculation rearranged to preserve intermediate precision.
 	 * Logically:
 	 * 1. "end - start" gives us the measurement period over all
 	 *    the square wave cycles.
 	 * 2. Divide by number of square wave cycles to get the period
 	 *    of a square wave cycle.
 	 * 3. Divide by 2*(int_out.fields.count+1), which is the formula
 	 *    by which the IOC4 generates the square wave, to get the
 	 *    period of an IOC4 INT_OUT count.
 	 */
 	end = end_ts.tv_sec * NSEC_PER_SEC + end_ts.tv_nsec;
 	start = start_ts.tv_sec * NSEC_PER_SEC + start_ts.tv_nsec;
 	period = (end - start) /
 		(IOC4_CALIBRATE_CYCLES * 2 * (IOC4_CALIBRATE_COUNT + 1));

 	/* Bounds check the result. */
 	if (period > IOC4_CALIBRATE_LOW_LIMIT ||
 	    period < IOC4_CALIBRATE_HIGH_LIMIT) {
 		printk(KERN_INFO
 		       "IOC4 %s: Clock calibration failed.  Assuming"
 		       "PCI clock is %d ns.\n",
 		       pci_name(idd->idd_pdev),
 		       IOC4_CALIBRATE_DEFAULT / IOC4_EXTINT_COUNT_DIVISOR);
 		period = IOC4_CALIBRATE_DEFAULT;
 	} else {
 		u64 ns = period;

 		do_div(ns, IOC4_EXTINT_COUNT_DIVISOR);
 		printk(KERN_DEBUG
 		       "IOC4 %s: PCI clock is %llu ns.\n",
 		       pci_name(idd->idd_pdev), (unsigned long long)ns);
 	}

 	/* Remember results.  We store the extint clock period rather
 	 * than the PCI clock period so that greater precision is
 	 * retained.  Divide by IOC4_EXTINT_COUNT_DIVISOR to get
 	 * PCI clock period.
 	 */
 	idd->count_period = period;
 }

 /* There are three variants of IOC4 cards: IO9, IO10, and PCI-RT.
  * Each brings out different combinations of IOC4 signals, thus.
  * the IOC4 subdrivers need to know to which we're attached.
  *
  * We look for the presence of a SCSI (IO9) or SATA (IO10) controller
  * on the same PCI bus at slot number 3 to differentiate IO9 from IO10.
  * If neither is present, it's a PCI-RT.
  */
 static unsigned int __devinit
 ioc4_variant(struct ioc4_driver_data *idd)
 {
 	struct pci_dev *pdev = NULL;
 	int found = 0;

 	/* IO9: Look for a QLogic ISP 12160 at the same bus and slot 3. */
 	do {
 		pdev = pci_get_device(PCI_VENDOR_ID_QLOGIC,
 				      PCI_DEVICE_ID_QLOGIC_ISP12160, pdev);
 		if (pdev &&
 		    idd->idd_pdev->bus->number == pdev->bus->number &&
 		    3 == PCI_SLOT(pdev->devfn))
 			found = 1;
 	} while (pdev && !found);
 	if (NULL != pdev) {
 		pci_dev_put(pdev);
 		return IOC4_VARIANT_IO9;
 	}

 	/* IO10: Look for a Vitesse VSC 7174 at the same bus and slot 3. */
 	pdev = NULL;
 	do {
 		pdev = pci_get_device(PCI_VENDOR_ID_VITESSE,
 				      PCI_DEVICE_ID_VITESSE_VSC7174, pdev);
 		if (pdev &&
 		    idd->idd_pdev->bus->number == pdev->bus->number &&
 		    3 == PCI_SLOT(pdev->devfn))
 			found = 1;
 	} while (pdev && !found);
 	if (NULL != pdev) {
 		pci_dev_put(pdev);
 		return IOC4_VARIANT_IO10;
 	}

 	/* PCI-RT: No SCSI/SATA controller will be present */
 	return IOC4_VARIANT_PCI_RT;
 }

 static void
 ioc4_load_modules(struct work_struct *work)
 {
 	request_module("sgiioc4");
 }

 static DECLARE_WORK(ioc4_load_modules_work, ioc4_load_modules);

 /* Adds a new instance of an IOC4 card */
 static int __devinit
 ioc4_probe(struct pci_dev *pdev, const struct pci_device_id *pci_id)
 {
 	struct ioc4_driver_data *idd;
 	struct ioc4_submodule *is;
 	uint32_t pcmd;
 	int ret;

 	/* Enable IOC4 and take ownership of it */
 	if ((ret = pci_enable_device(pdev))) {
 		printk(KERN_WARNING
 		       "%s: Failed to enable IOC4 device for pci_dev %s.\n",
 		       __func__, pci_name(pdev));
 		goto out;
 	}
 	pci_set_master(pdev);

 	/* Set up per-IOC4 data */
 	idd = kmalloc(sizeof(struct ioc4_driver_data), GFP_KERNEL);
 	if (!idd) {
 		printk(KERN_WARNING
 		       "%s: Failed to allocate IOC4 data for pci_dev %s.\n",
 		       __func__, pci_name(pdev));
 		ret = -ENODEV;
 		goto out_idd;
 	}
 	idd->idd_pdev = pdev;
 	idd->idd_pci_id = pci_id;

 	/* Map IOC4 misc registers.  These are shared between subdevices
 	 * so the main IOC4 module manages them.
 	 */
 	idd->idd_bar0 = pci_resource_start(idd->idd_pdev, 0);
 	if (!idd->idd_bar0) {
 		printk(KERN_WARNING
 		       "%s: Unable to find IOC4 misc resource "
 		       "for pci_dev %s.\n",
 		       __func__, pci_name(idd->idd_pdev));
 		ret = -ENODEV;
 		goto out_pci;
 	}
 	if (!request_mem_region(idd->idd_bar0, sizeof(struct ioc4_misc_regs),
 			    "ioc4_misc")) {
 		printk(KERN_WARNING
 		       "%s: Unable to request IOC4 misc region "
 		       "for pci_dev %s.\n",
 		       __func__, pci_name(idd->idd_pdev));
 		ret = -ENODEV;
 		goto out_pci;
 	}
 	idd->idd_misc_regs = ioremap(idd->idd_bar0,
 				     sizeof(struct ioc4_misc_regs));
 	if (!idd->idd_misc_regs) {
 		printk(KERN_WARNING
 		       "%s: Unable to remap IOC4 misc region "
 		       "for pci_dev %s.\n",
 		       __func__, pci_name(idd->idd_pdev));
 		ret = -ENODEV;
 		goto out_misc_region;
 	}

 	/* Failsafe portion of per-IOC4 initialization */

 	/* Detect card variant */
 	idd->idd_variant = ioc4_variant(idd);
 	printk(KERN_INFO "IOC4 %s: %s card detected.\n", pci_name(pdev),
 	       idd->idd_variant == IOC4_VARIANT_IO9 ? "IO9" :
 	       idd->idd_variant == IOC4_VARIANT_PCI_RT ? "PCI-RT" :
 	       idd->idd_variant == IOC4_VARIANT_IO10 ? "IO10" : "unknown");

 	/* Initialize IOC4 */
 	pci_read_config_dword(idd->idd_pdev, PCI_COMMAND, &pcmd);
 	pci_write_config_dword(idd->idd_pdev, PCI_COMMAND,
 			       pcmd | PCI_COMMAND_PARITY | PCI_COMMAND_SERR);

 	/* Determine PCI clock */
 	ioc4_clock_calibrate(idd);

 	/* Disable/clear all interrupts.  Need to do this here lest
 	 * one submodule request the shared IOC4 IRQ, but interrupt
 	 * is generated by a different subdevice.
 	 */
 	/* Disable */
 	writel(~0, &idd->idd_misc_regs->other_iec.raw);
 	writel(~0, &idd->idd_misc_regs->sio_iec);
 	/* Clear (i.e. acknowledge) */
 	writel(~0, &idd->idd_misc_regs->other_ir.raw);
 	writel(~0, &idd->idd_misc_regs->sio_ir);

 	/* Track PCI-device specific data */
 	idd->idd_serial_data = NULL;
 	pci_set_drvdata(idd->idd_pdev, idd);

 	mutex_lock(&ioc4_mutex);
 	list_add_tail(&idd->idd_list, &ioc4_devices);

 	/* Add this IOC4 to all submodules */
 	list_for_each_entry(is, &ioc4_submodules, is_list) {
 		if (is->is_probe && is->is_probe(idd)) {
 			printk(KERN_WARNING
 			       "%s: IOC4 submodule 0x%s probe failed "
 			       "for pci_dev %s.\n",
 			       __func__, module_name(is->is_owner),
 			       pci_name(idd->idd_pdev));
 		}
 	}
 	mutex_unlock(&ioc4_mutex);

 	/* Request sgiioc4 IDE driver on boards that bring that functionality
 	 * off of IOC4.  The root filesystem may be hosted on a drive connected
 	 * to IOC4, so we need to make sure the sgiioc4 driver is loaded as it
 	 * won't be picked up by modprobes due to the ioc4 module owning the
 	 * PCI device.
 	 */
 	if (idd->idd_variant != IOC4_VARIANT_PCI_RT) {
 		/* Request the module from a work procedure as the modprobe
 		 * goes out to a userland helper and that will hang if done
 		 * directly from ioc4_probe().
 		 */
 		printk(KERN_INFO "IOC4 loading sgiioc4 submodule\n");
 		schedule_work(&ioc4_load_modules_work);
 	}

 	return 0;

 out_misc_region:
 	release_mem_region(idd->idd_bar0, sizeof(struct ioc4_misc_regs));
 out_pci:
 	kfree(idd);
 out_idd:
 	pci_disable_device(pdev);
 out:
 	return ret;
 }

 /* Removes a particular instance of an IOC4 card. */
 static void __devexit
 ioc4_remove(struct pci_dev *pdev)
 {
 	struct ioc4_submodule *is;
 	struct ioc4_driver_data *idd;

 	idd = pci_get_drvdata(pdev);

 	/* Remove this IOC4 from all submodules */
 	mutex_lock(&ioc4_mutex);
 	list_for_each_entry(is, &ioc4_submodules, is_list) {
 		if (is->is_remove && is->is_remove(idd)) {
 			printk(KERN_WARNING
 			       "%s: IOC4 submodule 0x%s remove failed "
 			       "for pci_dev %s.\n",
 			       __func__, module_name(is->is_owner),
 			       pci_name(idd->idd_pdev));
 		}
 	}
 	mutex_unlock(&ioc4_mutex);

 	/* Release resources */
 	iounmap(idd->idd_misc_regs);
 	if (!idd->idd_bar0) {
 		printk(KERN_WARNING
 		       "%s: Unable to get IOC4 misc mapping for pci_dev %s. "
 		       "Device removal may be incomplete.\n",
 		       __func__, pci_name(idd->idd_pdev));
 	}
 	release_mem_region(idd->idd_bar0, sizeof(struct ioc4_misc_regs));

 	/* Disable IOC4 and relinquish */
 	pci_disable_device(pdev);

 	/* Remove and free driver data */
 	mutex_lock(&ioc4_mutex);
 	list_del(&idd->idd_list);
 	mutex_unlock(&ioc4_mutex);
 	kfree(idd);
 }

 static struct pci_device_id ioc4_id_table[] = {
 	{PCI_VENDOR_ID_SGI, PCI_DEVICE_ID_SGI_IOC4, PCI_ANY_ID,
 	 PCI_ANY_ID, 0x0b4000, 0xFFFFFF},
 	{0}
 };

 static struct pci_driver ioc4_driver = {
 	.name = "IOC4",
 	.id_table = ioc4_id_table,
 	.probe = ioc4_probe,
 	.remove = __devexit_p(ioc4_remove),
 };

 MODULE_DEVICE_TABLE(pci, ioc4_id_table);

 /*********************
  * Module management *
  *********************/

 /* Module load */
 static int __init
 ioc4_init(void)
 {
 	return pci_register_driver(&ioc4_driver);
 }

 /* Module unload */
 static void __exit
 ioc4_exit(void)
 {
 	/* Ensure ioc4_load_modules() has completed before exiting */
 	flush_work(&ioc4_load_modules_work);
 	pci_unregister_driver(&ioc4_driver);
 }

 module_init(ioc4_init);
 module_exit(ioc4_exit);

 MODULE_AUTHOR("Brent Casavant - Silicon Graphics, Inc. <bcasavan@sgi.com>");
 MODULE_DESCRIPTION("PCI driver master module for SGI IOC4 Base-IO Card");
 MODULE_LICENSE("GPL");

 EXPORT_SYMBOL(ioc4_register_submodule);
 EXPORT_SYMBOL(ioc4_unregister_submodule);
	/*
	* This file is subject to the terms and conditions of the GNU General Public
	* License. See the file "COPYING" in the main directory of this archive
	* for more details.
	*
	* Copyright (C) 2005-2006 Silicon Graphics, Inc. All Rights Reserved.
	*/

	/* This file contains the master driver module for use by SGI IOC4 subdrivers.
	*
	* It allocates any resources shared between multiple subdevices, and
	* provides accessor functions (where needed) and the like for those
	* resources. It also provides a mechanism for the subdevice modules
	* to support loading and unloading.
	*
	* Non-shared resources (e.g. external interrupt A_INT_OUT register page
	* alias, serial port and UART registers) are handled by the subdevice
	* modules themselves.
	*
	* This is all necessary because IOC4 is not implemented as a multi-function
	* PCI device, but an amalgamation of disparate registers for several
	* types of device (ATA, serial, external interrupts). The normal
	* resource management in the kernel doesn't have quite the right interfaces
	* to handle this situation (e.g. multiple modules can't claim the same
	* PCI ID), thus this IOC4 master module.
	*/

	#include <linux/errno.h>
	#include <linux/module.h>
	#include <linux/pci.h>
	#include <linux/ioc4.h>
	#include <linux/ktime.h>
	#include <linux/slab.h>
	#include <linux/mutex.h>
	#include <linux/time.h>
	#include <asm/io.h>

	/***************
	* Definitions *
	***************/

	/* Tweakable values */

	/* PCI bus speed detection/calibration */
	#define IOC4_CALIBRATE_COUNT 63 /* Calibration cycle period */
	#define IOC4_CALIBRATE_CYCLES 256 /* Average over this many cycles */
	#define IOC4_CALIBRATE_DISCARD 2 /* Discard first few cycles */
	#define IOC4_CALIBRATE_LOW_MHZ 25 /* Lower bound on bus speed sanity */
	#define IOC4_CALIBRATE_HIGH_MHZ 75 /* Upper bound on bus speed sanity */
	#define IOC4_CALIBRATE_DEFAULT_MHZ 66 /* Assumed if sanity check fails */

	/************************
	* Submodule management *
	************************/

	static DEFINE_MUTEX(ioc4_mutex);

	static LIST_HEAD(ioc4_devices);
	static LIST_HEAD(ioc4_submodules);

	/* Register an IOC4 submodule */
	int
	ioc4_register_submodule(struct ioc4_submodule *is)
	{
	struct ioc4_driver_data *idd;

	mutex_lock(&ioc4_mutex);
	list_add(&is->is_list, &ioc4_submodules);

	/* Initialize submodule for each IOC4 */
	if (!is->is_probe)
	goto out;

	list_for_each_entry(idd, &ioc4_devices, idd_list) {
	if (is->is_probe(idd)) {
	printk(KERN_WARNING
	"%s: IOC4 submodule %s probe failed "
	"for pci_dev %s",
	__func__, module_name(is->is_owner),
	pci_name(idd->idd_pdev));
	}
	}
	out:
	mutex_unlock(&ioc4_mutex);
	return 0;
	}

	/* Unregister an IOC4 submodule */
	void
	ioc4_unregister_submodule(struct ioc4_submodule *is)
	{
	struct ioc4_driver_data *idd;

	mutex_lock(&ioc4_mutex);
	list_del(&is->is_list);

	/* Remove submodule for each IOC4 */
	if (!is->is_remove)
	goto out;

	list_for_each_entry(idd, &ioc4_devices, idd_list) {
	if (is->is_remove(idd)) {
	printk(KERN_WARNING
	"%s: IOC4 submodule %s remove failed "
	"for pci_dev %s.\n",
	__func__, module_name(is->is_owner),
	pci_name(idd->idd_pdev));
	}
	}
	out:
	mutex_unlock(&ioc4_mutex);
	}

	/*********************
	* Device management *
	*********************/

	#define IOC4_CALIBRATE_LOW_LIMIT \
	(1000*IOC4_EXTINT_COUNT_DIVISOR/IOC4_CALIBRATE_LOW_MHZ)
	#define IOC4_CALIBRATE_HIGH_LIMIT \
	(1000*IOC4_EXTINT_COUNT_DIVISOR/IOC4_CALIBRATE_HIGH_MHZ)
	#define IOC4_CALIBRATE_DEFAULT \
	(1000*IOC4_EXTINT_COUNT_DIVISOR/IOC4_CALIBRATE_DEFAULT_MHZ)

	#define IOC4_CALIBRATE_END \
	(IOC4_CALIBRATE_CYCLES + IOC4_CALIBRATE_DISCARD)

	#define IOC4_INT_OUT_MODE_TOGGLE 0x7 /* Toggle INT_OUT every COUNT+1 ticks */

	/* Determines external interrupt output clock period of the PCI bus an
	* IOC4 is attached to. This value can be used to determine the PCI
	* bus speed.
	*
	* IOC4 has a design feature that various internal timers are derived from
	* the PCI bus clock. This causes IOC4 device drivers to need to take the
	* bus speed into account when setting various register values (e.g. INT_OUT
	* register COUNT field, UART divisors, etc). Since this information is
	* needed by several subdrivers, it is determined by the main IOC4 driver,
	* even though the following code utilizes external interrupt registers
	* to perform the speed calculation.
	*/
	static void __devinit
	ioc4_clock_calibrate(struct ioc4_driver_data *idd)
	{
	union ioc4_int_out int_out;
	union ioc4_gpcr gpcr;
	unsigned int state, last_state = 1;
	struct timespec start_ts, end_ts;
	uint64_t start, end, period;
	unsigned int count = 0;

	/* Enable output */
	gpcr.raw = 0;
	gpcr.fields.dir = IOC4_GPCR_DIR_0;
	gpcr.fields.int_out_en = 1;
	writel(gpcr.raw, &idd->idd_misc_regs->gpcr_s.raw);

	/* Reset to power-on state */
	writel(0, &idd->idd_misc_regs->int_out.raw);
	mmiowb();

	/* Set up square wave */
	int_out.raw = 0;
	int_out.fields.count = IOC4_CALIBRATE_COUNT;
	int_out.fields.mode = IOC4_INT_OUT_MODE_TOGGLE;
	int_out.fields.diag = 0;
	writel(int_out.raw, &idd->idd_misc_regs->int_out.raw);
	mmiowb();

	/* Check square wave period averaged over some number of cycles */
	do {
	int_out.raw = readl(&idd->idd_misc_regs->int_out.raw);
	state = int_out.fields.int_out;
	if (!last_state && state) {
	count++;
	if (count == IOC4_CALIBRATE_END) {
	ktime_get_ts(&end_ts);
	break;
	} else if (count == IOC4_CALIBRATE_DISCARD)
	ktime_get_ts(&start_ts);
	}
	last_state = state;
	} while (1);

	/* Calculation rearranged to preserve intermediate precision.
	* Logically:
	* 1. "end - start" gives us the measurement period over all
	* the square wave cycles.
	* 2. Divide by number of square wave cycles to get the period
	* of a square wave cycle.
	* 3. Divide by 2*(int_out.fields.count+1), which is the formula
	* by which the IOC4 generates the square wave, to get the
	* period of an IOC4 INT_OUT count.
	*/
	end = end_ts.tv_sec * NSEC_PER_SEC + end_ts.tv_nsec;
	start = start_ts.tv_sec * NSEC_PER_SEC + start_ts.tv_nsec;
	period = (end - start) /
	(IOC4_CALIBRATE_CYCLES * 2 * (IOC4_CALIBRATE_COUNT + 1));

	/* Bounds check the result. */
	if (period > IOC4_CALIBRATE_LOW_LIMIT \|\|
	period < IOC4_CALIBRATE_HIGH_LIMIT) {
	printk(KERN_INFO
	"IOC4 %s: Clock calibration failed. Assuming"
	"PCI clock is %d ns.\n",
	pci_name(idd->idd_pdev),
	IOC4_CALIBRATE_DEFAULT / IOC4_EXTINT_COUNT_DIVISOR);
	period = IOC4_CALIBRATE_DEFAULT;
	} else {
	u64 ns = period;

	do_div(ns, IOC4_EXTINT_COUNT_DIVISOR);
	printk(KERN_DEBUG
	"IOC4 %s: PCI clock is %llu ns.\n",
	pci_name(idd->idd_pdev), (unsigned long long)ns);
	}

	/* Remember results. We store the extint clock period rather
	* than the PCI clock period so that greater precision is
	* retained. Divide by IOC4_EXTINT_COUNT_DIVISOR to get
	* PCI clock period.
	*/
	idd->count_period = period;
	}

	/* There are three variants of IOC4 cards: IO9, IO10, and PCI-RT.
	* Each brings out different combinations of IOC4 signals, thus.
	* the IOC4 subdrivers need to know to which we're attached.
	*
	* We look for the presence of a SCSI (IO9) or SATA (IO10) controller
	* on the same PCI bus at slot number 3 to differentiate IO9 from IO10.
	* If neither is present, it's a PCI-RT.
	*/
	static unsigned int __devinit
	ioc4_variant(struct ioc4_driver_data *idd)
	{
	struct pci_dev *pdev = NULL;
	int found = 0;

	/* IO9: Look for a QLogic ISP 12160 at the same bus and slot 3. */
	do {
	pdev = pci_get_device(PCI_VENDOR_ID_QLOGIC,
	PCI_DEVICE_ID_QLOGIC_ISP12160, pdev);
	if (pdev &&
	idd->idd_pdev->bus->number == pdev->bus->number &&
	3 == PCI_SLOT(pdev->devfn))
	found = 1;
	} while (pdev && !found);
	if (NULL != pdev) {
	pci_dev_put(pdev);
	return IOC4_VARIANT_IO9;
	}

	/* IO10: Look for a Vitesse VSC 7174 at the same bus and slot 3. */
	pdev = NULL;
	do {
	pdev = pci_get_device(PCI_VENDOR_ID_VITESSE,
	PCI_DEVICE_ID_VITESSE_VSC7174, pdev);
	if (pdev &&
	idd->idd_pdev->bus->number == pdev->bus->number &&
	3 == PCI_SLOT(pdev->devfn))
	found = 1;
	} while (pdev && !found);
	if (NULL != pdev) {
	pci_dev_put(pdev);
	return IOC4_VARIANT_IO10;
	}

	/* PCI-RT: No SCSI/SATA controller will be present */
	return IOC4_VARIANT_PCI_RT;
	}

	static void
	ioc4_load_modules(struct work_struct *work)
	{
	request_module("sgiioc4");
	}

	static DECLARE_WORK(ioc4_load_modules_work, ioc4_load_modules);

	/* Adds a new instance of an IOC4 card */
	static int __devinit
	ioc4_probe(struct pci_dev pdev, const struct pci_device_id pci_id)
	{
	struct ioc4_driver_data *idd;
	struct ioc4_submodule *is;
	uint32_t pcmd;
	int ret;

	/* Enable IOC4 and take ownership of it */
	if ((ret = pci_enable_device(pdev))) {
	printk(KERN_WARNING
	"%s: Failed to enable IOC4 device for pci_dev %s.\n",
	__func__, pci_name(pdev));
	goto out;
	}
	pci_set_master(pdev);

	/* Set up per-IOC4 data */
	idd = kmalloc(sizeof(struct ioc4_driver_data), GFP_KERNEL);
	if (!idd) {
	printk(KERN_WARNING
	"%s: Failed to allocate IOC4 data for pci_dev %s.\n",
	__func__, pci_name(pdev));
	ret = -ENODEV;
	goto out_idd;
	}
	idd->idd_pdev = pdev;
	idd->idd_pci_id = pci_id;

	/* Map IOC4 misc registers. These are shared between subdevices
	* so the main IOC4 module manages them.
	*/
	idd->idd_bar0 = pci_resource_start(idd->idd_pdev, 0);
	if (!idd->idd_bar0) {
	printk(KERN_WARNING
	"%s: Unable to find IOC4 misc resource "
	"for pci_dev %s.\n",
	__func__, pci_name(idd->idd_pdev));
	ret = -ENODEV;
	goto out_pci;
	}
	if (!request_mem_region(idd->idd_bar0, sizeof(struct ioc4_misc_regs),
	"ioc4_misc")) {
	printk(KERN_WARNING
	"%s: Unable to request IOC4 misc region "
	"for pci_dev %s.\n",
	__func__, pci_name(idd->idd_pdev));
	ret = -ENODEV;
	goto out_pci;
	}
	idd->idd_misc_regs = ioremap(idd->idd_bar0,
	sizeof(struct ioc4_misc_regs));
	if (!idd->idd_misc_regs) {
	printk(KERN_WARNING
	"%s: Unable to remap IOC4 misc region "
	"for pci_dev %s.\n",
	__func__, pci_name(idd->idd_pdev));
	ret = -ENODEV;
	goto out_misc_region;
	}

	/* Failsafe portion of per-IOC4 initialization */

	/* Detect card variant */
	idd->idd_variant = ioc4_variant(idd);
	printk(KERN_INFO "IOC4 %s: %s card detected.\n", pci_name(pdev),
	idd->idd_variant == IOC4_VARIANT_IO9 ? "IO9" :
	idd->idd_variant == IOC4_VARIANT_PCI_RT ? "PCI-RT" :
	idd->idd_variant == IOC4_VARIANT_IO10 ? "IO10" : "unknown");

	/* Initialize IOC4 */
	pci_read_config_dword(idd->idd_pdev, PCI_COMMAND, &pcmd);
	pci_write_config_dword(idd->idd_pdev, PCI_COMMAND,
	pcmd \| PCI_COMMAND_PARITY \| PCI_COMMAND_SERR);

	/* Determine PCI clock */
	ioc4_clock_calibrate(idd);

	/* Disable/clear all interrupts. Need to do this here lest
	* one submodule request the shared IOC4 IRQ, but interrupt
	* is generated by a different subdevice.
	*/
	/* Disable */
	writel(~0, &idd->idd_misc_regs->other_iec.raw);
	writel(~0, &idd->idd_misc_regs->sio_iec);
	/* Clear (i.e. acknowledge) */
	writel(~0, &idd->idd_misc_regs->other_ir.raw);
	writel(~0, &idd->idd_misc_regs->sio_ir);

	/* Track PCI-device specific data */
	idd->idd_serial_data = NULL;
	pci_set_drvdata(idd->idd_pdev, idd);

	mutex_lock(&ioc4_mutex);
	list_add_tail(&idd->idd_list, &ioc4_devices);

	/* Add this IOC4 to all submodules */
	list_for_each_entry(is, &ioc4_submodules, is_list) {
	if (is->is_probe && is->is_probe(idd)) {
	printk(KERN_WARNING
	"%s: IOC4 submodule 0x%s probe failed "
	"for pci_dev %s.\n",
	__func__, module_name(is->is_owner),
	pci_name(idd->idd_pdev));
	}
	}
	mutex_unlock(&ioc4_mutex);

	/* Request sgiioc4 IDE driver on boards that bring that functionality
	* off of IOC4. The root filesystem may be hosted on a drive connected
	* to IOC4, so we need to make sure the sgiioc4 driver is loaded as it
	* won't be picked up by modprobes due to the ioc4 module owning the
	* PCI device.
	*/
	if (idd->idd_variant != IOC4_VARIANT_PCI_RT) {
	/* Request the module from a work procedure as the modprobe
	* goes out to a userland helper and that will hang if done
	* directly from ioc4_probe().
	*/
	printk(KERN_INFO "IOC4 loading sgiioc4 submodule\n");
	schedule_work(&ioc4_load_modules_work);
	}

	return 0;

	out_misc_region:
	release_mem_region(idd->idd_bar0, sizeof(struct ioc4_misc_regs));
	out_pci:
	kfree(idd);
	out_idd:
	pci_disable_device(pdev);
	out:
	return ret;
	}

	/* Removes a particular instance of an IOC4 card. */
	static void __devexit
	ioc4_remove(struct pci_dev *pdev)
	{
	struct ioc4_submodule *is;
	struct ioc4_driver_data *idd;

	idd = pci_get_drvdata(pdev);

	/* Remove this IOC4 from all submodules */
	mutex_lock(&ioc4_mutex);
	list_for_each_entry(is, &ioc4_submodules, is_list) {
	if (is->is_remove && is->is_remove(idd)) {
	printk(KERN_WARNING
	"%s: IOC4 submodule 0x%s remove failed "
	"for pci_dev %s.\n",
	__func__, module_name(is->is_owner),
	pci_name(idd->idd_pdev));
	}
	}
	mutex_unlock(&ioc4_mutex);

	/* Release resources */
	iounmap(idd->idd_misc_regs);
	if (!idd->idd_bar0) {
	printk(KERN_WARNING
	"%s: Unable to get IOC4 misc mapping for pci_dev %s. "
	"Device removal may be incomplete.\n",
	__func__, pci_name(idd->idd_pdev));
	}
	release_mem_region(idd->idd_bar0, sizeof(struct ioc4_misc_regs));

	/* Disable IOC4 and relinquish */
	pci_disable_device(pdev);

	/* Remove and free driver data */
	mutex_lock(&ioc4_mutex);
	list_del(&idd->idd_list);
	mutex_unlock(&ioc4_mutex);
	kfree(idd);
	}

	static struct pci_device_id ioc4_id_table[] = {
	{PCI_VENDOR_ID_SGI, PCI_DEVICE_ID_SGI_IOC4, PCI_ANY_ID,
	PCI_ANY_ID, 0x0b4000, 0xFFFFFF},
	{0}
	};

	static struct pci_driver ioc4_driver = {
	.name = "IOC4",
	.id_table = ioc4_id_table,
	.probe = ioc4_probe,
	.remove = __devexit_p(ioc4_remove),
	};

	MODULE_DEVICE_TABLE(pci, ioc4_id_table);

	/*********************
	* Module management *
	*********************/

	/* Module load */
	static int __init
	ioc4_init(void)
	{
	return pci_register_driver(&ioc4_driver);
	}

	/* Module unload */
	static void __exit
	ioc4_exit(void)
	{
	/* Ensure ioc4_load_modules() has completed before exiting */
	flush_work(&ioc4_load_modules_work);
	pci_unregister_driver(&ioc4_driver);
	}

	module_init(ioc4_init);
	module_exit(ioc4_exit);

	MODULE_AUTHOR("Brent Casavant - Silicon Graphics, Inc. <bcasavan@sgi.com>");
	MODULE_DESCRIPTION("PCI driver master module for SGI IOC4 Base-IO Card");
	MODULE_LICENSE("GPL");

	EXPORT_SYMBOL(ioc4_register_submodule);
	EXPORT_SYMBOL(ioc4_unregister_submodule);