drivers/mailbox/pcc.c - kernel/msm-4.9 - Gitiles

 /*
  *	Copyright (C) 2014 Linaro Ltd.
  *	Author:	Ashwin Chaugule <ashwin.chaugule@linaro.org>
  *
  *  This program is free software; you can redistribute it and/or modify
  *  it under the terms of the GNU General Public License as published by
  *  the Free Software Foundation; either version 2 of the License, or
  *  (at your option) any later version.
  *
  *  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.
  *
  *  PCC (Platform Communication Channel) is defined in the ACPI 5.0+
  *  specification. It is a mailbox like mechanism to allow clients
  *  such as CPPC (Collaborative Processor Performance Control), RAS
  *  (Reliability, Availability and Serviceability) and MPST (Memory
  *  Node Power State Table) to talk to the platform (e.g. BMC) through
  *  shared memory regions as defined in the PCC table entries. The PCC
  *  specification supports a Doorbell mechanism for the PCC clients
  *  to notify the platform about new data. This Doorbell information
  *  is also specified in each PCC table entry.
  *
  *  Typical high level flow of operation is:
  *
  *  PCC Reads:
  *  * Client tries to acquire a channel lock.
  *  * After it is acquired it writes READ cmd in communication region cmd
  *		address.
  *  * Client issues mbox_send_message() which rings the PCC doorbell
  *		for its PCC channel.
  *  * If command completes, then client has control over channel and
  *		it can proceed with its reads.
  *  * Client releases lock.
  *
  *  PCC Writes:
  *  * Client tries to acquire channel lock.
  *  * Client writes to its communication region after it acquires a
  *		channel lock.
  *  * Client writes WRITE cmd in communication region cmd address.
  *  * Client issues mbox_send_message() which rings the PCC doorbell
  *		for its PCC channel.
  *  * If command completes, then writes have succeded and it can release
  *		the channel lock.
  *
  *  There is a Nominal latency defined for each channel which indicates
  *  how long to wait until a command completes. If command is not complete
  *  the client needs to retry or assume failure.
  *
  *	For more details about PCC, please see the ACPI specification from
  *  http://www.uefi.org/ACPIv5.1 Section 14.
  *
  *  This file implements PCC as a Mailbox controller and allows for PCC
  *  clients to be implemented as its Mailbox Client Channels.
  */

 #include <linux/acpi.h>
 #include <linux/delay.h>
 #include <linux/io.h>
 #include <linux/init.h>
 #include <linux/list.h>
 #include <linux/platform_device.h>
 #include <linux/mailbox_controller.h>
 #include <linux/mailbox_client.h>
 #include <linux/io-64-nonatomic-lo-hi.h>

 #include "mailbox.h"

 #define MAX_PCC_SUBSPACES	256

 static struct mbox_chan *pcc_mbox_channels;

 /* Array of cached virtual address for doorbell registers */
 static void __iomem **pcc_doorbell_vaddr;

 static struct mbox_controller pcc_mbox_ctrl = {};
 /**
  * get_pcc_channel - Given a PCC subspace idx, get
  *	the respective mbox_channel.
  * @id: PCC subspace index.
  *
  * Return: ERR_PTR(errno) if error, else pointer
  *	to mbox channel.
  */
 static struct mbox_chan *get_pcc_channel(int id)
 {
 	if (id < 0 || id > pcc_mbox_ctrl.num_chans)
 		return ERR_PTR(-ENOENT);

 	return &pcc_mbox_channels[id];
 }

 /**
  * pcc_mbox_request_channel - PCC clients call this function to
  *		request a pointer to their PCC subspace, from which they
  *		can get the details of communicating with the remote.
  * @cl: Pointer to Mailbox client, so we know where to bind the
  *		Channel.
  * @subspace_id: The PCC Subspace index as parsed in the PCC client
  *		ACPI package. This is used to lookup the array of PCC
  *		subspaces as parsed by the PCC Mailbox controller.
  *
  * Return: Pointer to the Mailbox Channel if successful or
  *		ERR_PTR.
  */
 struct mbox_chan *pcc_mbox_request_channel(struct mbox_client *cl,
 		int subspace_id)
 {
 	struct device *dev = pcc_mbox_ctrl.dev;
 	struct mbox_chan *chan;
 	unsigned long flags;

 	/*
 	 * Each PCC Subspace is a Mailbox Channel.
 	 * The PCC Clients get their PCC Subspace ID
 	 * from their own tables and pass it here.
 	 * This returns a pointer to the PCC subspace
 	 * for the Client to operate on.
 	 */
 	chan = get_pcc_channel(subspace_id);

 	if (IS_ERR(chan) || chan->cl) {
 		dev_err(dev, "Channel not found for idx: %d\n", subspace_id);
 		return ERR_PTR(-EBUSY);
 	}

 	spin_lock_irqsave(&chan->lock, flags);
 	chan->msg_free = 0;
 	chan->msg_count = 0;
 	chan->active_req = NULL;
 	chan->cl = cl;
 	init_completion(&chan->tx_complete);

 	if (chan->txdone_method == TXDONE_BY_POLL && cl->knows_txdone)
 		chan->txdone_method |= TXDONE_BY_ACK;

 	spin_unlock_irqrestore(&chan->lock, flags);

 	return chan;
 }
 EXPORT_SYMBOL_GPL(pcc_mbox_request_channel);

 /**
  * pcc_mbox_free_channel - Clients call this to free their Channel.
  *
  * @chan: Pointer to the mailbox channel as returned by
  *		pcc_mbox_request_channel()
  */
 void pcc_mbox_free_channel(struct mbox_chan *chan)
 {
 	unsigned long flags;

 	if (!chan || !chan->cl)
 		return;

 	spin_lock_irqsave(&chan->lock, flags);
 	chan->cl = NULL;
 	chan->active_req = NULL;
 	if (chan->txdone_method == (TXDONE_BY_POLL | TXDONE_BY_ACK))
 		chan->txdone_method = TXDONE_BY_POLL;

 	spin_unlock_irqrestore(&chan->lock, flags);
 }
 EXPORT_SYMBOL_GPL(pcc_mbox_free_channel);

 /*
  * PCC can be used with perf critical drivers such as CPPC
  * So it makes sense to locally cache the virtual address and
  * use it to read/write to PCC registers such as doorbell register
  *
  * The below read_register and write_registers are used to read and
  * write from perf critical registers such as PCC doorbell register
  */
 static int read_register(void __iomem *vaddr, u64 *val, unsigned int bit_width)
 {
 	int ret_val = 0;

 	switch (bit_width) {
 	case 8:
 		*val = readb(vaddr);
 		break;
 	case 16:
 		*val = readw(vaddr);
 		break;
 	case 32:
 		*val = readl(vaddr);
 		break;
 	case 64:
 		*val = readq(vaddr);
 		break;
 	default:
 		pr_debug("Error: Cannot read register of %u bit width",
 			bit_width);
 		ret_val = -EFAULT;
 		break;
 	}
 	return ret_val;
 }

 static int write_register(void __iomem *vaddr, u64 val, unsigned int bit_width)
 {
 	int ret_val = 0;

 	switch (bit_width) {
 	case 8:
 		writeb(val, vaddr);
 		break;
 	case 16:
 		writew(val, vaddr);
 		break;
 	case 32:
 		writel(val, vaddr);
 		break;
 	case 64:
 		writeq(val, vaddr);
 		break;
 	default:
 		pr_debug("Error: Cannot write register of %u bit width",
 			bit_width);
 		ret_val = -EFAULT;
 		break;
 	}
 	return ret_val;
 }

 /**
  * pcc_send_data - Called from Mailbox Controller code. Used
  *		here only to ring the channel doorbell. The PCC client
  *		specific read/write is done in the client driver in
  *		order to maintain atomicity over PCC channel once
  *		OS has control over it. See above for flow of operations.
  * @chan: Pointer to Mailbox channel over which to send data.
  * @data: Client specific data written over channel. Used here
  *		only for debug after PCC transaction completes.
  *
  * Return: Err if something failed else 0 for success.
  */
 static int pcc_send_data(struct mbox_chan *chan, void *data)
 {
 	struct acpi_pcct_hw_reduced *pcct_ss = chan->con_priv;
 	struct acpi_generic_address *doorbell;
 	u64 doorbell_preserve;
 	u64 doorbell_val;
 	u64 doorbell_write;
 	u32 id = chan - pcc_mbox_channels;
 	int ret = 0;

 	if (id >= pcc_mbox_ctrl.num_chans) {
 		pr_debug("pcc_send_data: Invalid mbox_chan passed\n");
 		return -ENOENT;
 	}

 	doorbell = &pcct_ss->doorbell_register;
 	doorbell_preserve = pcct_ss->preserve_mask;
 	doorbell_write = pcct_ss->write_mask;

 	/* Sync notification from OS to Platform. */
 	if (pcc_doorbell_vaddr[id]) {
 		ret = read_register(pcc_doorbell_vaddr[id], &doorbell_val,
 			doorbell->bit_width);
 		if (ret)
 			return ret;
 		ret = write_register(pcc_doorbell_vaddr[id],
 			(doorbell_val & doorbell_preserve) | doorbell_write,
 			doorbell->bit_width);
 	} else {
 		ret = acpi_read(&doorbell_val, doorbell);
 		if (ret)
 			return ret;
 		ret = acpi_write((doorbell_val & doorbell_preserve) | doorbell_write,
 			doorbell);
 	}
 	return ret;
 }

 static const struct mbox_chan_ops pcc_chan_ops = {
 	.send_data = pcc_send_data,
 };

 /**
  * parse_pcc_subspace - Parse the PCC table and verify PCC subspace
  *		entries. There should be one entry per PCC client.
  * @header: Pointer to the ACPI subtable header under the PCCT.
  * @end: End of subtable entry.
  *
  * Return: 0 for Success, else errno.
  *
  * This gets called for each entry in the PCC table.
  */
 static int parse_pcc_subspace(struct acpi_subtable_header *header,
 		const unsigned long end)
 {
 	struct acpi_pcct_hw_reduced *pcct_ss;

 	if (pcc_mbox_ctrl.num_chans <= MAX_PCC_SUBSPACES) {
 		pcct_ss = (struct acpi_pcct_hw_reduced *) header;

 		if (pcct_ss->header.type !=
 				ACPI_PCCT_TYPE_HW_REDUCED_SUBSPACE) {
 			pr_err("Incorrect PCC Subspace type detected\n");
 			return -EINVAL;
 		}
 	}

 	return 0;
 }

 /**
  * acpi_pcc_probe - Parse the ACPI tree for the PCCT.
  *
  * Return: 0 for Success, else errno.
  */
 static int __init acpi_pcc_probe(void)
 {
 	acpi_size pcct_tbl_header_size;
 	struct acpi_table_header *pcct_tbl;
 	struct acpi_subtable_header *pcct_entry;
 	int count, i;
 	acpi_status status = AE_OK;

 	/* Search for PCCT */
 	status = acpi_get_table_with_size(ACPI_SIG_PCCT, 0,
 			&pcct_tbl,
 			&pcct_tbl_header_size);

 	if (ACPI_FAILURE(status) || !pcct_tbl) {
 		pr_warn("PCCT header not found.\n");
 		return -ENODEV;
 	}

 	count = acpi_table_parse_entries(ACPI_SIG_PCCT,
 			sizeof(struct acpi_table_pcct),
 			ACPI_PCCT_TYPE_HW_REDUCED_SUBSPACE,
 			parse_pcc_subspace, MAX_PCC_SUBSPACES);

 	if (count <= 0) {
 		pr_err("Error parsing PCC subspaces from PCCT\n");
 		return -EINVAL;
 	}

 	pcc_mbox_channels = kzalloc(sizeof(struct mbox_chan) *
 			count, GFP_KERNEL);

 	if (!pcc_mbox_channels) {
 		pr_err("Could not allocate space for PCC mbox channels\n");
 		return -ENOMEM;
 	}

 	pcc_doorbell_vaddr = kcalloc(count, sizeof(void *), GFP_KERNEL);
 	if (!pcc_doorbell_vaddr) {
 		kfree(pcc_mbox_channels);
 		return -ENOMEM;
 	}

 	/* Point to the first PCC subspace entry */
 	pcct_entry = (struct acpi_subtable_header *) (
 		(unsigned long) pcct_tbl + sizeof(struct acpi_table_pcct));

 	for (i = 0; i < count; i++) {
 		struct acpi_generic_address *db_reg;
 		struct acpi_pcct_hw_reduced *pcct_ss;
 		pcc_mbox_channels[i].con_priv = pcct_entry;

 		/* If doorbell is in system memory cache the virt address */
 		pcct_ss = (struct acpi_pcct_hw_reduced *)pcct_entry;
 		db_reg = &pcct_ss->doorbell_register;
 		if (db_reg->space_id == ACPI_ADR_SPACE_SYSTEM_MEMORY)
 			pcc_doorbell_vaddr[i] = acpi_os_ioremap(db_reg->address,
 							db_reg->bit_width/8);
 		pcct_entry = (struct acpi_subtable_header *)
 			((unsigned long) pcct_entry + pcct_entry->length);
 	}

 	pcc_mbox_ctrl.num_chans = count;

 	pr_info("Detected %d PCC Subspaces\n", pcc_mbox_ctrl.num_chans);

 	return 0;
 }

 /**
  * pcc_mbox_probe - Called when we find a match for the
  *	PCCT platform device. This is purely used to represent
  *	the PCCT as a virtual device for registering with the
  *	generic Mailbox framework.
  *
  * @pdev: Pointer to platform device returned when a match
  *	is found.
  *
  *	Return: 0 for Success, else errno.
  */
 static int pcc_mbox_probe(struct platform_device *pdev)
 {
 	int ret = 0;

 	pcc_mbox_ctrl.chans = pcc_mbox_channels;
 	pcc_mbox_ctrl.ops = &pcc_chan_ops;
 	pcc_mbox_ctrl.dev = &pdev->dev;

 	pr_info("Registering PCC driver as Mailbox controller\n");
 	ret = mbox_controller_register(&pcc_mbox_ctrl);

 	if (ret) {
 		pr_err("Err registering PCC as Mailbox controller: %d\n", ret);
 		ret = -ENODEV;
 	}

 	return ret;
 }

 struct platform_driver pcc_mbox_driver = {
 	.probe = pcc_mbox_probe,
 	.driver = {
 		.name = "PCCT",
 		.owner = THIS_MODULE,
 	},
 };

 static int __init pcc_init(void)
 {
 	int ret;
 	struct platform_device *pcc_pdev;

 	if (acpi_disabled)
 		return -ENODEV;

 	/* Check if PCC support is available. */
 	ret = acpi_pcc_probe();

 	if (ret) {
 		pr_debug("ACPI PCC probe failed.\n");
 		return -ENODEV;
 	}

 	pcc_pdev = platform_create_bundle(&pcc_mbox_driver,
 			pcc_mbox_probe, NULL, 0, NULL, 0);

 	if (IS_ERR(pcc_pdev)) {
 		pr_debug("Err creating PCC platform bundle\n");
 		return PTR_ERR(pcc_pdev);
 	}

 	return 0;
 }

 /*
  * Make PCC init postcore so that users of this mailbox
  * such as the ACPI Processor driver have it available
  * at their init.
  */
 postcore_initcall(pcc_init);
	/*
	* Copyright (C) 2014 Linaro Ltd.
	* Author: Ashwin Chaugule <ashwin.chaugule@linaro.org>
	*
	* This program is free software; you can redistribute it and/or modify
	* it under the terms of the GNU General Public License as published by
	* the Free Software Foundation; either version 2 of the License, or
	* (at your option) any later version.
	*
	* 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.
	*
	* PCC (Platform Communication Channel) is defined in the ACPI 5.0+
	* specification. It is a mailbox like mechanism to allow clients
	* such as CPPC (Collaborative Processor Performance Control), RAS
	* (Reliability, Availability and Serviceability) and MPST (Memory
	* Node Power State Table) to talk to the platform (e.g. BMC) through
	* shared memory regions as defined in the PCC table entries. The PCC
	* specification supports a Doorbell mechanism for the PCC clients
	* to notify the platform about new data. This Doorbell information
	* is also specified in each PCC table entry.
	*
	* Typical high level flow of operation is:
	*
	* PCC Reads:
	* * Client tries to acquire a channel lock.
	* * After it is acquired it writes READ cmd in communication region cmd
	* address.
	* * Client issues mbox_send_message() which rings the PCC doorbell
	* for its PCC channel.
	* * If command completes, then client has control over channel and
	* it can proceed with its reads.
	* * Client releases lock.
	*
	* PCC Writes:
	* * Client tries to acquire channel lock.
	* * Client writes to its communication region after it acquires a
	* channel lock.
	* * Client writes WRITE cmd in communication region cmd address.
	* * Client issues mbox_send_message() which rings the PCC doorbell
	* for its PCC channel.
	* * If command completes, then writes have succeded and it can release
	* the channel lock.
	*
	* There is a Nominal latency defined for each channel which indicates
	* how long to wait until a command completes. If command is not complete
	* the client needs to retry or assume failure.
	*
	* For more details about PCC, please see the ACPI specification from
	* http://www.uefi.org/ACPIv5.1 Section 14.
	*
	* This file implements PCC as a Mailbox controller and allows for PCC
	* clients to be implemented as its Mailbox Client Channels.
	*/

	#include <linux/acpi.h>
	#include <linux/delay.h>
	#include <linux/io.h>
	#include <linux/init.h>
	#include <linux/list.h>
	#include <linux/platform_device.h>
	#include <linux/mailbox_controller.h>
	#include <linux/mailbox_client.h>
	#include <linux/io-64-nonatomic-lo-hi.h>

	#include "mailbox.h"

	#define MAX_PCC_SUBSPACES 256

	static struct mbox_chan *pcc_mbox_channels;

	/* Array of cached virtual address for doorbell registers */
	static void __iomem **pcc_doorbell_vaddr;

	static struct mbox_controller pcc_mbox_ctrl = {};
	/**
	* get_pcc_channel - Given a PCC subspace idx, get
	* the respective mbox_channel.
	* @id: PCC subspace index.
	*
	* Return: ERR_PTR(errno) if error, else pointer
	* to mbox channel.
	*/
	static struct mbox_chan *get_pcc_channel(int id)
	{
	if (id < 0 \|\| id > pcc_mbox_ctrl.num_chans)
	return ERR_PTR(-ENOENT);

	return &pcc_mbox_channels[id];
	}

	/**
	* pcc_mbox_request_channel - PCC clients call this function to
	* request a pointer to their PCC subspace, from which they
	* can get the details of communicating with the remote.
	* @cl: Pointer to Mailbox client, so we know where to bind the
	* Channel.
	* @subspace_id: The PCC Subspace index as parsed in the PCC client
	* ACPI package. This is used to lookup the array of PCC
	* subspaces as parsed by the PCC Mailbox controller.
	*
	* Return: Pointer to the Mailbox Channel if successful or
	* ERR_PTR.
	*/
	struct mbox_chan pcc_mbox_request_channel(struct mbox_client cl,
	int subspace_id)
	{
	struct device *dev = pcc_mbox_ctrl.dev;
	struct mbox_chan *chan;
	unsigned long flags;

	/*
	* Each PCC Subspace is a Mailbox Channel.
	* The PCC Clients get their PCC Subspace ID
	* from their own tables and pass it here.
	* This returns a pointer to the PCC subspace
	* for the Client to operate on.
	*/
	chan = get_pcc_channel(subspace_id);

	if (IS_ERR(chan) \|\| chan->cl) {
	dev_err(dev, "Channel not found for idx: %d\n", subspace_id);
	return ERR_PTR(-EBUSY);
	}

	spin_lock_irqsave(&chan->lock, flags);
	chan->msg_free = 0;
	chan->msg_count = 0;
	chan->active_req = NULL;
	chan->cl = cl;
	init_completion(&chan->tx_complete);

	if (chan->txdone_method == TXDONE_BY_POLL && cl->knows_txdone)
	chan->txdone_method \|= TXDONE_BY_ACK;

	spin_unlock_irqrestore(&chan->lock, flags);

	return chan;
	}
	EXPORT_SYMBOL_GPL(pcc_mbox_request_channel);

	/**
	* pcc_mbox_free_channel - Clients call this to free their Channel.
	*
	* @chan: Pointer to the mailbox channel as returned by
	* pcc_mbox_request_channel()
	*/
	void pcc_mbox_free_channel(struct mbox_chan *chan)
	{
	unsigned long flags;

	if (!chan \|\| !chan->cl)
	return;

	spin_lock_irqsave(&chan->lock, flags);
	chan->cl = NULL;
	chan->active_req = NULL;
	if (chan->txdone_method == (TXDONE_BY_POLL \| TXDONE_BY_ACK))
	chan->txdone_method = TXDONE_BY_POLL;

	spin_unlock_irqrestore(&chan->lock, flags);
	}
	EXPORT_SYMBOL_GPL(pcc_mbox_free_channel);

	/*
	* PCC can be used with perf critical drivers such as CPPC
	* So it makes sense to locally cache the virtual address and
	* use it to read/write to PCC registers such as doorbell register
	*
	* The below read_register and write_registers are used to read and
	* write from perf critical registers such as PCC doorbell register
	*/
	static int read_register(void __iomem vaddr, u64 val, unsigned int bit_width)
	{
	int ret_val = 0;

	switch (bit_width) {
	case 8:
	*val = readb(vaddr);
	break;
	case 16:
	*val = readw(vaddr);
	break;
	case 32:
	*val = readl(vaddr);
	break;
	case 64:
	*val = readq(vaddr);
	break;
	default:
	pr_debug("Error: Cannot read register of %u bit width",
	bit_width);
	ret_val = -EFAULT;
	break;
	}
	return ret_val;
	}

	static int write_register(void __iomem *vaddr, u64 val, unsigned int bit_width)
	{
	int ret_val = 0;

	switch (bit_width) {
	case 8:
	writeb(val, vaddr);
	break;
	case 16:
	writew(val, vaddr);
	break;
	case 32:
	writel(val, vaddr);
	break;
	case 64:
	writeq(val, vaddr);
	break;
	default:
	pr_debug("Error: Cannot write register of %u bit width",
	bit_width);
	ret_val = -EFAULT;
	break;
	}
	return ret_val;
	}

	/**
	* pcc_send_data - Called from Mailbox Controller code. Used
	* here only to ring the channel doorbell. The PCC client
	* specific read/write is done in the client driver in
	* order to maintain atomicity over PCC channel once
	* OS has control over it. See above for flow of operations.
	* @chan: Pointer to Mailbox channel over which to send data.
	* @data: Client specific data written over channel. Used here
	* only for debug after PCC transaction completes.
	*
	* Return: Err if something failed else 0 for success.
	*/
	static int pcc_send_data(struct mbox_chan chan, void data)
	{
	struct acpi_pcct_hw_reduced *pcct_ss = chan->con_priv;
	struct acpi_generic_address *doorbell;
	u64 doorbell_preserve;
	u64 doorbell_val;
	u64 doorbell_write;
	u32 id = chan - pcc_mbox_channels;
	int ret = 0;

	if (id >= pcc_mbox_ctrl.num_chans) {
	pr_debug("pcc_send_data: Invalid mbox_chan passed\n");
	return -ENOENT;
	}

	doorbell = &pcct_ss->doorbell_register;
	doorbell_preserve = pcct_ss->preserve_mask;
	doorbell_write = pcct_ss->write_mask;

	/* Sync notification from OS to Platform. */
	if (pcc_doorbell_vaddr[id]) {
	ret = read_register(pcc_doorbell_vaddr[id], &doorbell_val,
	doorbell->bit_width);
	if (ret)
	return ret;
	ret = write_register(pcc_doorbell_vaddr[id],
	(doorbell_val & doorbell_preserve) \| doorbell_write,
	doorbell->bit_width);
	} else {
	ret = acpi_read(&doorbell_val, doorbell);
	if (ret)
	return ret;
	ret = acpi_write((doorbell_val & doorbell_preserve) \| doorbell_write,
	doorbell);
	}
	return ret;
	}

	static const struct mbox_chan_ops pcc_chan_ops = {
	.send_data = pcc_send_data,
	};

	/**
	* parse_pcc_subspace - Parse the PCC table and verify PCC subspace
	* entries. There should be one entry per PCC client.
	* @header: Pointer to the ACPI subtable header under the PCCT.
	* @end: End of subtable entry.
	*
	* Return: 0 for Success, else errno.
	*
	* This gets called for each entry in the PCC table.
	*/
	static int parse_pcc_subspace(struct acpi_subtable_header *header,
	const unsigned long end)
	{
	struct acpi_pcct_hw_reduced *pcct_ss;

	if (pcc_mbox_ctrl.num_chans <= MAX_PCC_SUBSPACES) {
	pcct_ss = (struct acpi_pcct_hw_reduced *) header;

	if (pcct_ss->header.type !=
	ACPI_PCCT_TYPE_HW_REDUCED_SUBSPACE) {
	pr_err("Incorrect PCC Subspace type detected\n");
	return -EINVAL;
	}
	}

	return 0;
	}

	/**
	* acpi_pcc_probe - Parse the ACPI tree for the PCCT.
	*
	* Return: 0 for Success, else errno.
	*/
	static int __init acpi_pcc_probe(void)
	{
	acpi_size pcct_tbl_header_size;
	struct acpi_table_header *pcct_tbl;
	struct acpi_subtable_header *pcct_entry;
	int count, i;
	acpi_status status = AE_OK;

	/* Search for PCCT */
	status = acpi_get_table_with_size(ACPI_SIG_PCCT, 0,
	&pcct_tbl,
	&pcct_tbl_header_size);

	if (ACPI_FAILURE(status) \|\| !pcct_tbl) {
	pr_warn("PCCT header not found.\n");
	return -ENODEV;
	}

	count = acpi_table_parse_entries(ACPI_SIG_PCCT,
	sizeof(struct acpi_table_pcct),
	ACPI_PCCT_TYPE_HW_REDUCED_SUBSPACE,
	parse_pcc_subspace, MAX_PCC_SUBSPACES);

	if (count <= 0) {
	pr_err("Error parsing PCC subspaces from PCCT\n");
	return -EINVAL;
	}

	pcc_mbox_channels = kzalloc(sizeof(struct mbox_chan) *
	count, GFP_KERNEL);

	if (!pcc_mbox_channels) {
	pr_err("Could not allocate space for PCC mbox channels\n");
	return -ENOMEM;
	}

	pcc_doorbell_vaddr = kcalloc(count, sizeof(void *), GFP_KERNEL);
	if (!pcc_doorbell_vaddr) {
	kfree(pcc_mbox_channels);
	return -ENOMEM;
	}

	/* Point to the first PCC subspace entry */
	pcct_entry = (struct acpi_subtable_header *) (
	(unsigned long) pcct_tbl + sizeof(struct acpi_table_pcct));

	for (i = 0; i < count; i++) {
	struct acpi_generic_address *db_reg;
	struct acpi_pcct_hw_reduced *pcct_ss;
	pcc_mbox_channels[i].con_priv = pcct_entry;

	/* If doorbell is in system memory cache the virt address */
	pcct_ss = (struct acpi_pcct_hw_reduced *)pcct_entry;
	db_reg = &pcct_ss->doorbell_register;
	if (db_reg->space_id == ACPI_ADR_SPACE_SYSTEM_MEMORY)
	pcc_doorbell_vaddr[i] = acpi_os_ioremap(db_reg->address,
	db_reg->bit_width/8);
	pcct_entry = (struct acpi_subtable_header *)
	((unsigned long) pcct_entry + pcct_entry->length);
	}

	pcc_mbox_ctrl.num_chans = count;

	pr_info("Detected %d PCC Subspaces\n", pcc_mbox_ctrl.num_chans);

	return 0;
	}

	/**
	* pcc_mbox_probe - Called when we find a match for the
	* PCCT platform device. This is purely used to represent
	* the PCCT as a virtual device for registering with the
	* generic Mailbox framework.
	*
	* @pdev: Pointer to platform device returned when a match
	* is found.
	*
	* Return: 0 for Success, else errno.
	*/
	static int pcc_mbox_probe(struct platform_device *pdev)
	{
	int ret = 0;

	pcc_mbox_ctrl.chans = pcc_mbox_channels;
	pcc_mbox_ctrl.ops = &pcc_chan_ops;
	pcc_mbox_ctrl.dev = &pdev->dev;

	pr_info("Registering PCC driver as Mailbox controller\n");
	ret = mbox_controller_register(&pcc_mbox_ctrl);

	if (ret) {
	pr_err("Err registering PCC as Mailbox controller: %d\n", ret);
	ret = -ENODEV;
	}

	return ret;
	}

	struct platform_driver pcc_mbox_driver = {
	.probe = pcc_mbox_probe,
	.driver = {
	.name = "PCCT",
	.owner = THIS_MODULE,
	},
	};

	static int __init pcc_init(void)
	{
	int ret;
	struct platform_device *pcc_pdev;

	if (acpi_disabled)
	return -ENODEV;

	/* Check if PCC support is available. */
	ret = acpi_pcc_probe();

	if (ret) {
	pr_debug("ACPI PCC probe failed.\n");
	return -ENODEV;
	}

	pcc_pdev = platform_create_bundle(&pcc_mbox_driver,
	pcc_mbox_probe, NULL, 0, NULL, 0);

	if (IS_ERR(pcc_pdev)) {
	pr_debug("Err creating PCC platform bundle\n");
	return PTR_ERR(pcc_pdev);
	}

	return 0;
	}

	/*
	* Make PCC init postcore so that users of this mailbox
	* such as the ACPI Processor driver have it available
	* at their init.
	*/
	postcore_initcall(pcc_init);