drivers/usb/host/xhci-hub.c - fp2-dev/kernel/msm - Gitiles

 /*
  * xHCI host controller driver
  *
  * Copyright (C) 2008 Intel Corp.
  *
  * Author: Sarah Sharp
  * Some code borrowed from the Linux EHCI driver.
  *
  * 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.
  *
  * You should have received a copy of the GNU General Public License
  * along with this program; if not, write to the Free Software Foundation,
  * Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  */

 #include <asm/unaligned.h>

 #include "xhci.h"

 static void xhci_hub_descriptor(struct xhci_hcd *xhci,
 		struct usb_hub_descriptor *desc)
 {
 	int ports;
 	u16 temp;

 	ports = HCS_MAX_PORTS(xhci->hcs_params1);

 	/* USB 3.0 hubs have a different descriptor, but we fake this for now */
 	desc->bDescriptorType = 0x29;
 	desc->bPwrOn2PwrGood = 10;	/* xhci section 5.4.9 says 20ms max */
 	desc->bHubContrCurrent = 0;

 	desc->bNbrPorts = ports;
 	temp = 1 + (ports / 8);
 	desc->bDescLength = 7 + 2 * temp;

 	/* Why does core/hcd.h define bitmap?  It's just confusing. */
 	memset(&desc->DeviceRemovable[0], 0, temp);
 	memset(&desc->DeviceRemovable[temp], 0xff, temp);

 	/* Ugh, these should be #defines, FIXME */
 	/* Using table 11-13 in USB 2.0 spec. */
 	temp = 0;
 	/* Bits 1:0 - support port power switching, or power always on */
 	if (HCC_PPC(xhci->hcc_params))
 		temp |= 0x0001;
 	else
 		temp |= 0x0002;
 	/* Bit  2 - root hubs are not part of a compound device */
 	/* Bits 4:3 - individual port over current protection */
 	temp |= 0x0008;
 	/* Bits 6:5 - no TTs in root ports */
 	/* Bit  7 - no port indicators */
 	desc->wHubCharacteristics = (__force __u16) cpu_to_le16(temp);
 }

 static unsigned int xhci_port_speed(unsigned int port_status)
 {
 	if (DEV_LOWSPEED(port_status))
 		return 1 << USB_PORT_FEAT_LOWSPEED;
 	if (DEV_HIGHSPEED(port_status))
 		return 1 << USB_PORT_FEAT_HIGHSPEED;
 	if (DEV_SUPERSPEED(port_status))
 		return 1 << USB_PORT_FEAT_SUPERSPEED;
 	/*
 	 * FIXME: Yes, we should check for full speed, but the core uses that as
 	 * a default in portspeed() in usb/core/hub.c (which is the only place
 	 * USB_PORT_FEAT_*SPEED is used).
 	 */
 	return 0;
 }

 /*
  * These bits are Read Only (RO) and should be saved and written to the
  * registers: 0, 3, 10:13, 30
  * connect status, over-current status, port speed, and device removable.
  * connect status and port speed are also sticky - meaning they're in
  * the AUX well and they aren't changed by a hot, warm, or cold reset.
  */
 #define	XHCI_PORT_RO	((1<<0) | (1<<3) | (0xf<<10) | (1<<30))
 /*
  * These bits are RW; writing a 0 clears the bit, writing a 1 sets the bit:
  * bits 5:8, 9, 14:15, 25:27
  * link state, port power, port indicator state, "wake on" enable state
  */
 #define XHCI_PORT_RWS	((0xf<<5) | (1<<9) | (0x3<<14) | (0x7<<25))
 /*
  * These bits are RW; writing a 1 sets the bit, writing a 0 has no effect:
  * bit 4 (port reset)
  */
 #define	XHCI_PORT_RW1S	((1<<4))
 /*
  * These bits are RW; writing a 1 clears the bit, writing a 0 has no effect:
  * bits 1, 17, 18, 19, 20, 21, 22, 23
  * port enable/disable, and
  * change bits: connect, PED, warm port reset changed (reserved zero for USB 2.0 ports),
  * over-current, reset, link state, and L1 change
  */
 #define XHCI_PORT_RW1CS	((1<<1) | (0x7f<<17))
 /*
  * Bit 16 is RW, and writing a '1' to it causes the link state control to be
  * latched in
  */
 #define	XHCI_PORT_RW	((1<<16))
 /*
  * These bits are Reserved Zero (RsvdZ) and zero should be written to them:
  * bits 2, 24, 28:31
  */
 #define	XHCI_PORT_RZ	((1<<2) | (1<<24) | (0xf<<28))

 /*
  * Given a port state, this function returns a value that would result in the
  * port being in the same state, if the value was written to the port status
  * control register.
  * Save Read Only (RO) bits and save read/write bits where
  * writing a 0 clears the bit and writing a 1 sets the bit (RWS).
  * For all other types (RW1S, RW1CS, RW, and RZ), writing a '0' has no effect.
  */
 static u32 xhci_port_state_to_neutral(u32 state)
 {
 	/* Save read-only status and port state */
 	return (state & XHCI_PORT_RO) | (state & XHCI_PORT_RWS);
 }

 static void xhci_disable_port(struct xhci_hcd *xhci, u16 wIndex,
 		u32 __iomem *addr, u32 port_status)
 {
 	/* Write 1 to disable the port */
 	xhci_writel(xhci, port_status | PORT_PE, addr);
 	port_status = xhci_readl(xhci, addr);
 	xhci_dbg(xhci, "disable port, actual port %d status  = 0x%x\n",
 			wIndex, port_status);
 }

 static void xhci_clear_port_change_bit(struct xhci_hcd *xhci, u16 wValue,
 		u16 wIndex, u32 __iomem *addr, u32 port_status)
 {
 	char *port_change_bit;
 	u32 status;

 	switch (wValue) {
 	case USB_PORT_FEAT_C_RESET:
 		status = PORT_RC;
 		port_change_bit = "reset";
 		break;
 	case USB_PORT_FEAT_C_CONNECTION:
 		status = PORT_CSC;
 		port_change_bit = "connect";
 		break;
 	case USB_PORT_FEAT_C_OVER_CURRENT:
 		status = PORT_OCC;
 		port_change_bit = "over-current";
 		break;
 	case USB_PORT_FEAT_C_ENABLE:
 		status = PORT_PEC;
 		port_change_bit = "enable/disable";
 		break;
 	default:
 		/* Should never happen */
 		return;
 	}
 	/* Change bits are all write 1 to clear */
 	xhci_writel(xhci, port_status | status, addr);
 	port_status = xhci_readl(xhci, addr);
 	xhci_dbg(xhci, "clear port %s change, actual port %d status  = 0x%x\n",
 			port_change_bit, wIndex, port_status);
 }

 int xhci_hub_control(struct usb_hcd *hcd, u16 typeReq, u16 wValue,
 		u16 wIndex, char *buf, u16 wLength)
 {
 	struct xhci_hcd	*xhci = hcd_to_xhci(hcd);
 	int ports;
 	unsigned long flags;
 	u32 temp, status;
 	int retval = 0;
 	u32 __iomem *addr;

 	ports = HCS_MAX_PORTS(xhci->hcs_params1);

 	spin_lock_irqsave(&xhci->lock, flags);
 	switch (typeReq) {
 	case GetHubStatus:
 		/* No power source, over-current reported per port */
 		memset(buf, 0, 4);
 		break;
 	case GetHubDescriptor:
 		xhci_hub_descriptor(xhci, (struct usb_hub_descriptor *) buf);
 		break;
 	case GetPortStatus:
 		if (!wIndex || wIndex > ports)
 			goto error;
 		wIndex--;
 		status = 0;
 		addr = &xhci->op_regs->port_status_base + NUM_PORT_REGS*(wIndex & 0xff);
 		temp = xhci_readl(xhci, addr);
 		xhci_dbg(xhci, "get port status, actual port %d status  = 0x%x\n", wIndex, temp);

 		/* wPortChange bits */
 		if (temp & PORT_CSC)
 			status |= 1 << USB_PORT_FEAT_C_CONNECTION;
 		if (temp & PORT_PEC)
 			status |= 1 << USB_PORT_FEAT_C_ENABLE;
 		if ((temp & PORT_OCC))
 			status |= 1 << USB_PORT_FEAT_C_OVER_CURRENT;
 		/*
 		 * FIXME ignoring suspend, reset, and USB 2.1/3.0 specific
 		 * changes
 		 */
 		if (temp & PORT_CONNECT) {
 			status |= 1 << USB_PORT_FEAT_CONNECTION;
 			status |= xhci_port_speed(temp);
 		}
 		if (temp & PORT_PE)
 			status |= 1 << USB_PORT_FEAT_ENABLE;
 		if (temp & PORT_OC)
 			status |= 1 << USB_PORT_FEAT_OVER_CURRENT;
 		if (temp & PORT_RESET)
 			status |= 1 << USB_PORT_FEAT_RESET;
 		if (temp & PORT_POWER)
 			status |= 1 << USB_PORT_FEAT_POWER;
 		xhci_dbg(xhci, "Get port status returned 0x%x\n", status);
 		put_unaligned(cpu_to_le32(status), (__le32 *) buf);
 		break;
 	case SetPortFeature:
 		wIndex &= 0xff;
 		if (!wIndex || wIndex > ports)
 			goto error;
 		wIndex--;
 		addr = &xhci->op_regs->port_status_base + NUM_PORT_REGS*(wIndex & 0xff);
 		temp = xhci_readl(xhci, addr);
 		temp = xhci_port_state_to_neutral(temp);
 		switch (wValue) {
 		case USB_PORT_FEAT_POWER:
 			/*
 			 * Turn on ports, even if there isn't per-port switching.
 			 * HC will report connect events even before this is set.
 			 * However, khubd will ignore the roothub events until
 			 * the roothub is registered.
 			 */
 			xhci_writel(xhci, temp | PORT_POWER, addr);

 			temp = xhci_readl(xhci, addr);
 			xhci_dbg(xhci, "set port power, actual port %d status  = 0x%x\n", wIndex, temp);
 			break;
 		case USB_PORT_FEAT_RESET:
 			temp = (temp | PORT_RESET);
 			xhci_writel(xhci, temp, addr);

 			temp = xhci_readl(xhci, addr);
 			xhci_dbg(xhci, "set port reset, actual port %d status  = 0x%x\n", wIndex, temp);
 			break;
 		default:
 			goto error;
 		}
 		temp = xhci_readl(xhci, addr); /* unblock any posted writes */
 		break;
 	case ClearPortFeature:
 		if (!wIndex || wIndex > ports)
 			goto error;
 		wIndex--;
 		addr = &xhci->op_regs->port_status_base +
 			NUM_PORT_REGS*(wIndex & 0xff);
 		temp = xhci_readl(xhci, addr);
 		temp = xhci_port_state_to_neutral(temp);
 		switch (wValue) {
 		case USB_PORT_FEAT_C_RESET:
 		case USB_PORT_FEAT_C_CONNECTION:
 		case USB_PORT_FEAT_C_OVER_CURRENT:
 		case USB_PORT_FEAT_C_ENABLE:
 			xhci_clear_port_change_bit(xhci, wValue, wIndex,
 					addr, temp);
 			break;
 		case USB_PORT_FEAT_ENABLE:
 			xhci_disable_port(xhci, wIndex, addr, temp);
 			break;
 		default:
 			goto error;
 		}
 		break;
 	default:
 error:
 		/* "stall" on error */
 		retval = -EPIPE;
 	}
 	spin_unlock_irqrestore(&xhci->lock, flags);
 	return retval;
 }

 /*
  * Returns 0 if the status hasn't changed, or the number of bytes in buf.
  * Ports are 0-indexed from the HCD point of view,
  * and 1-indexed from the USB core pointer of view.
  * xHCI instances can have up to 127 ports, so FIXME if you see more than 15.
  *
  * Note that the status change bits will be cleared as soon as a port status
  * change event is generated, so we use the saved status from that event.
  */
 int xhci_hub_status_data(struct usb_hcd *hcd, char *buf)
 {
 	unsigned long flags;
 	u32 temp, status;
 	int i, retval;
 	struct xhci_hcd	*xhci = hcd_to_xhci(hcd);
 	int ports;
 	u32 __iomem *addr;

 	ports = HCS_MAX_PORTS(xhci->hcs_params1);

 	/* Initial status is no changes */
 	buf[0] = 0;
 	status = 0;
 	if (ports > 7) {
 		buf[1] = 0;
 		retval = 2;
 	} else {
 		retval = 1;
 	}

 	spin_lock_irqsave(&xhci->lock, flags);
 	/* For each port, did anything change?  If so, set that bit in buf. */
 	for (i = 0; i < ports; i++) {
 		addr = &xhci->op_regs->port_status_base +
 			NUM_PORT_REGS*i;
 		temp = xhci_readl(xhci, addr);
 		if (temp & (PORT_CSC | PORT_PEC | PORT_OCC)) {
 			if (i < 7)
 				buf[0] |= 1 << (i + 1);
 			else
 				buf[1] |= 1 << (i - 7);
 			status = 1;
 		}
 	}
 	spin_unlock_irqrestore(&xhci->lock, flags);
 	return status ? retval : 0;
 }
	/*
	* xHCI host controller driver
	*
	* Copyright (C) 2008 Intel Corp.
	*
	* Author: Sarah Sharp
	* Some code borrowed from the Linux EHCI driver.
	*
	* 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.
	*
	* You should have received a copy of the GNU General Public License
	* along with this program; if not, write to the Free Software Foundation,
	* Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
	*/

	#include <asm/unaligned.h>

	#include "xhci.h"

	static void xhci_hub_descriptor(struct xhci_hcd *xhci,
	struct usb_hub_descriptor *desc)
	{
	int ports;
	u16 temp;

	ports = HCS_MAX_PORTS(xhci->hcs_params1);

	/* USB 3.0 hubs have a different descriptor, but we fake this for now */
	desc->bDescriptorType = 0x29;
	desc->bPwrOn2PwrGood = 10; /* xhci section 5.4.9 says 20ms max */
	desc->bHubContrCurrent = 0;

	desc->bNbrPorts = ports;
	temp = 1 + (ports / 8);
	desc->bDescLength = 7 + 2 * temp;

	/* Why does core/hcd.h define bitmap? It's just confusing. */
	memset(&desc->DeviceRemovable[0], 0, temp);
	memset(&desc->DeviceRemovable[temp], 0xff, temp);

	/* Ugh, these should be #defines, FIXME */
	/* Using table 11-13 in USB 2.0 spec. */
	temp = 0;
	/* Bits 1:0 - support port power switching, or power always on */
	if (HCC_PPC(xhci->hcc_params))
	temp \|= 0x0001;
	else
	temp \|= 0x0002;
	/* Bit 2 - root hubs are not part of a compound device */
	/* Bits 4:3 - individual port over current protection */
	temp \|= 0x0008;
	/* Bits 6:5 - no TTs in root ports */
	/* Bit 7 - no port indicators */
	desc->wHubCharacteristics = (__force __u16) cpu_to_le16(temp);
	}

	static unsigned int xhci_port_speed(unsigned int port_status)
	{
	if (DEV_LOWSPEED(port_status))
	return 1 << USB_PORT_FEAT_LOWSPEED;
	if (DEV_HIGHSPEED(port_status))
	return 1 << USB_PORT_FEAT_HIGHSPEED;
	if (DEV_SUPERSPEED(port_status))
	return 1 << USB_PORT_FEAT_SUPERSPEED;
	/*
	* FIXME: Yes, we should check for full speed, but the core uses that as
	* a default in portspeed() in usb/core/hub.c (which is the only place
	* USB_PORT_FEAT_*SPEED is used).
	*/
	return 0;
	}

	/*
	* These bits are Read Only (RO) and should be saved and written to the
	* registers: 0, 3, 10:13, 30
	* connect status, over-current status, port speed, and device removable.
	* connect status and port speed are also sticky - meaning they're in
	* the AUX well and they aren't changed by a hot, warm, or cold reset.
	*/
	#define XHCI_PORT_RO ((1<<0) \| (1<<3) \| (0xf<<10) \| (1<<30))
	/*
	* These bits are RW; writing a 0 clears the bit, writing a 1 sets the bit:
	* bits 5:8, 9, 14:15, 25:27
	* link state, port power, port indicator state, "wake on" enable state
	*/
	#define XHCI_PORT_RWS ((0xf<<5) \| (1<<9) \| (0x3<<14) \| (0x7<<25))
	/*
	* These bits are RW; writing a 1 sets the bit, writing a 0 has no effect:
	* bit 4 (port reset)
	*/
	#define XHCI_PORT_RW1S ((1<<4))
	/*
	* These bits are RW; writing a 1 clears the bit, writing a 0 has no effect:
	* bits 1, 17, 18, 19, 20, 21, 22, 23
	* port enable/disable, and
	* change bits: connect, PED, warm port reset changed (reserved zero for USB 2.0 ports),
	* over-current, reset, link state, and L1 change
	*/
	#define XHCI_PORT_RW1CS ((1<<1) \| (0x7f<<17))
	/*
	* Bit 16 is RW, and writing a '1' to it causes the link state control to be
	* latched in
	*/
	#define XHCI_PORT_RW ((1<<16))
	/*
	* These bits are Reserved Zero (RsvdZ) and zero should be written to them:
	* bits 2, 24, 28:31
	*/
	#define XHCI_PORT_RZ ((1<<2) \| (1<<24) \| (0xf<<28))

	/*
	* Given a port state, this function returns a value that would result in the
	* port being in the same state, if the value was written to the port status
	* control register.
	* Save Read Only (RO) bits and save read/write bits where
	* writing a 0 clears the bit and writing a 1 sets the bit (RWS).
	* For all other types (RW1S, RW1CS, RW, and RZ), writing a '0' has no effect.
	*/
	static u32 xhci_port_state_to_neutral(u32 state)
	{
	/* Save read-only status and port state */
	return (state & XHCI_PORT_RO) \| (state & XHCI_PORT_RWS);
	}

	static void xhci_disable_port(struct xhci_hcd *xhci, u16 wIndex,
	u32 __iomem *addr, u32 port_status)
	{
	/* Write 1 to disable the port */
	xhci_writel(xhci, port_status \| PORT_PE, addr);
	port_status = xhci_readl(xhci, addr);
	xhci_dbg(xhci, "disable port, actual port %d status = 0x%x\n",
	wIndex, port_status);
	}

	static void xhci_clear_port_change_bit(struct xhci_hcd *xhci, u16 wValue,
	u16 wIndex, u32 __iomem *addr, u32 port_status)
	{
	char *port_change_bit;
	u32 status;

	switch (wValue) {
	case USB_PORT_FEAT_C_RESET:
	status = PORT_RC;
	port_change_bit = "reset";
	break;
	case USB_PORT_FEAT_C_CONNECTION:
	status = PORT_CSC;
	port_change_bit = "connect";
	break;
	case USB_PORT_FEAT_C_OVER_CURRENT:
	status = PORT_OCC;
	port_change_bit = "over-current";
	break;
	case USB_PORT_FEAT_C_ENABLE:
	status = PORT_PEC;
	port_change_bit = "enable/disable";
	break;
	default:
	/* Should never happen */
	return;
	}
	/* Change bits are all write 1 to clear */
	xhci_writel(xhci, port_status \| status, addr);
	port_status = xhci_readl(xhci, addr);
	xhci_dbg(xhci, "clear port %s change, actual port %d status = 0x%x\n",
	port_change_bit, wIndex, port_status);
	}

	int xhci_hub_control(struct usb_hcd *hcd, u16 typeReq, u16 wValue,
	u16 wIndex, char *buf, u16 wLength)
	{
	struct xhci_hcd *xhci = hcd_to_xhci(hcd);
	int ports;
	unsigned long flags;
	u32 temp, status;
	int retval = 0;
	u32 __iomem *addr;

	ports = HCS_MAX_PORTS(xhci->hcs_params1);

	spin_lock_irqsave(&xhci->lock, flags);
	switch (typeReq) {
	case GetHubStatus:
	/* No power source, over-current reported per port */
	memset(buf, 0, 4);
	break;
	case GetHubDescriptor:
	xhci_hub_descriptor(xhci, (struct usb_hub_descriptor *) buf);
	break;
	case GetPortStatus:
	if (!wIndex \|\| wIndex > ports)
	goto error;
	wIndex--;
	status = 0;
	addr = &xhci->op_regs->port_status_base + NUM_PORT_REGS*(wIndex & 0xff);
	temp = xhci_readl(xhci, addr);
	xhci_dbg(xhci, "get port status, actual port %d status = 0x%x\n", wIndex, temp);

	/* wPortChange bits */
	if (temp & PORT_CSC)
	status \|= 1 << USB_PORT_FEAT_C_CONNECTION;
	if (temp & PORT_PEC)
	status \|= 1 << USB_PORT_FEAT_C_ENABLE;
	if ((temp & PORT_OCC))
	status \|= 1 << USB_PORT_FEAT_C_OVER_CURRENT;
	/*
	* FIXME ignoring suspend, reset, and USB 2.1/3.0 specific
	* changes
	*/
	if (temp & PORT_CONNECT) {
	status \|= 1 << USB_PORT_FEAT_CONNECTION;
	status \|= xhci_port_speed(temp);
	}
	if (temp & PORT_PE)
	status \|= 1 << USB_PORT_FEAT_ENABLE;
	if (temp & PORT_OC)
	status \|= 1 << USB_PORT_FEAT_OVER_CURRENT;
	if (temp & PORT_RESET)
	status \|= 1 << USB_PORT_FEAT_RESET;
	if (temp & PORT_POWER)
	status \|= 1 << USB_PORT_FEAT_POWER;
	xhci_dbg(xhci, "Get port status returned 0x%x\n", status);
	put_unaligned(cpu_to_le32(status), (__le32 *) buf);
	break;
	case SetPortFeature:
	wIndex &= 0xff;
	if (!wIndex \|\| wIndex > ports)
	goto error;
	wIndex--;
	addr = &xhci->op_regs->port_status_base + NUM_PORT_REGS*(wIndex & 0xff);
	temp = xhci_readl(xhci, addr);
	temp = xhci_port_state_to_neutral(temp);
	switch (wValue) {
	case USB_PORT_FEAT_POWER:
	/*
	* Turn on ports, even if there isn't per-port switching.
	* HC will report connect events even before this is set.
	* However, khubd will ignore the roothub events until
	* the roothub is registered.
	*/
	xhci_writel(xhci, temp \| PORT_POWER, addr);

	temp = xhci_readl(xhci, addr);
	xhci_dbg(xhci, "set port power, actual port %d status = 0x%x\n", wIndex, temp);
	break;
	case USB_PORT_FEAT_RESET:
	temp = (temp \| PORT_RESET);
	xhci_writel(xhci, temp, addr);

	temp = xhci_readl(xhci, addr);
	xhci_dbg(xhci, "set port reset, actual port %d status = 0x%x\n", wIndex, temp);
	break;
	default:
	goto error;
	}
	temp = xhci_readl(xhci, addr); /* unblock any posted writes */
	break;
	case ClearPortFeature:
	if (!wIndex \|\| wIndex > ports)
	goto error;
	wIndex--;
	addr = &xhci->op_regs->port_status_base +
	NUM_PORT_REGS*(wIndex & 0xff);
	temp = xhci_readl(xhci, addr);
	temp = xhci_port_state_to_neutral(temp);
	switch (wValue) {
	case USB_PORT_FEAT_C_RESET:
	case USB_PORT_FEAT_C_CONNECTION:
	case USB_PORT_FEAT_C_OVER_CURRENT:
	case USB_PORT_FEAT_C_ENABLE:
	xhci_clear_port_change_bit(xhci, wValue, wIndex,
	addr, temp);
	break;
	case USB_PORT_FEAT_ENABLE:
	xhci_disable_port(xhci, wIndex, addr, temp);
	break;
	default:
	goto error;
	}
	break;
	default:
	error:
	/* "stall" on error */
	retval = -EPIPE;
	}
	spin_unlock_irqrestore(&xhci->lock, flags);
	return retval;
	}

	/*
	* Returns 0 if the status hasn't changed, or the number of bytes in buf.
	* Ports are 0-indexed from the HCD point of view,
	* and 1-indexed from the USB core pointer of view.
	* xHCI instances can have up to 127 ports, so FIXME if you see more than 15.
	*
	* Note that the status change bits will be cleared as soon as a port status
	* change event is generated, so we use the saved status from that event.
	*/
	int xhci_hub_status_data(struct usb_hcd hcd, char buf)
	{
	unsigned long flags;
	u32 temp, status;
	int i, retval;
	struct xhci_hcd *xhci = hcd_to_xhci(hcd);
	int ports;
	u32 __iomem *addr;

	ports = HCS_MAX_PORTS(xhci->hcs_params1);

	/* Initial status is no changes */
	buf[0] = 0;
	status = 0;
	if (ports > 7) {
	buf[1] = 0;
	retval = 2;
	} else {
	retval = 1;
	}

	spin_lock_irqsave(&xhci->lock, flags);
	/* For each port, did anything change? If so, set that bit in buf. */
	for (i = 0; i < ports; i++) {
	addr = &xhci->op_regs->port_status_base +
	NUM_PORT_REGS*i;
	temp = xhci_readl(xhci, addr);
	if (temp & (PORT_CSC \| PORT_PEC \| PORT_OCC)) {
	if (i < 7)
	buf[0] \|= 1 << (i + 1);
	else
	buf[1] \|= 1 << (i - 7);
	status = 1;
	}
	}
	spin_unlock_irqrestore(&xhci->lock, flags);
	return status ? retval : 0;
	}