/*
   *	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/interrupt.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 <acpi/pcc.h>

  
  #include "mailbox.h"
  
  #define MAX_PCC_SUBSPACES	256

  #define MBOX_IRQ_NAME		"pcc-mbox"

  
  static struct mbox_chan *pcc_mbox_channels;

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

  /* Array of cached virtual address for doorbell ack registers */
  static void __iomem **pcc_doorbell_ack_vaddr;
  /* Array of doorbell interrupts */
  static int *pcc_doorbell_irq;

  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 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_map_interrupt - Map a PCC subspace GSI to a linux IRQ number
   * @interrupt: GSI number.
   * @flags: interrupt flags
   *
   * Returns: a valid linux IRQ number on success
   *		0 or -EINVAL on failure
   */
  static int pcc_map_interrupt(u32 interrupt, u32 flags)
  {
  	int trigger, polarity;
  
  	if (!interrupt)
  		return 0;
  
  	trigger = (flags & ACPI_PCCT_INTERRUPT_MODE) ? ACPI_EDGE_SENSITIVE
  			: ACPI_LEVEL_SENSITIVE;
  
  	polarity = (flags & ACPI_PCCT_INTERRUPT_POLARITY) ? ACPI_ACTIVE_LOW
  			: ACPI_ACTIVE_HIGH;
  
  	return acpi_register_gsi(NULL, interrupt, trigger, polarity);
  }
  
  /**
   * pcc_mbox_irq - PCC mailbox interrupt handler
   */
  static irqreturn_t pcc_mbox_irq(int irq, void *p)
  {
  	struct acpi_generic_address *doorbell_ack;
  	struct acpi_pcct_hw_reduced *pcct_ss;
  	struct mbox_chan *chan = p;
  	u64 doorbell_ack_preserve;
  	u64 doorbell_ack_write;
  	u64 doorbell_ack_val;
  	int ret;
  
  	pcct_ss = chan->con_priv;
  
  	mbox_chan_received_data(chan, NULL);
  
  	if (pcct_ss->header.type == ACPI_PCCT_TYPE_HW_REDUCED_SUBSPACE_TYPE2) {
  		struct acpi_pcct_hw_reduced_type2 *pcct2_ss = chan->con_priv;
  		u32 id = chan - pcc_mbox_channels;
  
  		doorbell_ack = &pcct2_ss->doorbell_ack_register;
  		doorbell_ack_preserve = pcct2_ss->ack_preserve_mask;
  		doorbell_ack_write = pcct2_ss->ack_write_mask;
  
  		ret = read_register(pcc_doorbell_ack_vaddr[id],
  				    &doorbell_ack_val,
  				    doorbell_ack->bit_width);
  		if (ret)
  			return IRQ_NONE;
  
  		ret = write_register(pcc_doorbell_ack_vaddr[id],
  				     (doorbell_ack_val & doorbell_ack_preserve)
  					| doorbell_ack_write,
  				     doorbell_ack->bit_width);
  		if (ret)
  			return IRQ_NONE;
  	}
  
  	return IRQ_HANDLED;
  }

  /**

   * 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
  ", 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);

  	if (pcc_doorbell_irq[subspace_id] > 0) {
  		int rc;
  
  		rc = devm_request_irq(dev, pcc_doorbell_irq[subspace_id],
  				      pcc_mbox_irq, 0, MBOX_IRQ_NAME, chan);
  		if (unlikely(rc)) {
  			dev_err(dev, "failed to register PCC interrupt %d
  ",
  				pcc_doorbell_irq[subspace_id]);

  			pcc_mbox_free_channel(chan);

  			chan = ERR_PTR(rc);
  		}
  	}

  	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)
  {

  	u32 id = chan - pcc_mbox_channels;

  	unsigned long flags;
  
  	if (!chan || !chan->cl)
  		return;

  	if (id >= pcc_mbox_ctrl.num_chans) {
  		pr_debug("pcc_mbox_free_channel: Invalid mbox_chan passed
  ");
  		return;
  	}

  	if (pcc_doorbell_irq[id] > 0)
  		devm_free_irq(chan->mbox->dev, pcc_doorbell_irq[id], chan);

  	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_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
  ");
  		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)
  		    && (pcct_ss->header.type !=
  				ACPI_PCCT_TYPE_HW_REDUCED_SUBSPACE_TYPE2)) {

  			pr_err("Incorrect PCC Subspace type detected
  ");
  			return -EINVAL;
  		}
  	}
  
  	return 0;
  }
  
  /**

   * pcc_parse_subspace_irq - Parse the PCC IRQ and PCC ACK register
   *		There should be one entry per PCC client.
   * @id: PCC subspace index.
   * @pcct_ss: Pointer to the ACPI subtable header under the PCCT.
   *
   * Return: 0 for Success, else errno.
   *
   * This gets called for each entry in the PCC table.
   */
  static int pcc_parse_subspace_irq(int id,
  				  struct acpi_pcct_hw_reduced *pcct_ss)
  {
  	pcc_doorbell_irq[id] = pcc_map_interrupt(pcct_ss->doorbell_interrupt,
  						 (u32)pcct_ss->flags);
  	if (pcc_doorbell_irq[id] <= 0) {
  		pr_err("PCC GSI %d not registered
  ",
  		       pcct_ss->doorbell_interrupt);
  		return -EINVAL;
  	}
  
  	if (pcct_ss->header.type
  		== ACPI_PCCT_TYPE_HW_REDUCED_SUBSPACE_TYPE2) {
  		struct acpi_pcct_hw_reduced_type2 *pcct2_ss = (void *)pcct_ss;
  
  		pcc_doorbell_ack_vaddr[id] = acpi_os_ioremap(
  				pcct2_ss->doorbell_ack_register.address,
  				pcct2_ss->doorbell_ack_register.bit_width / 8);
  		if (!pcc_doorbell_ack_vaddr[id]) {
  			pr_err("Failed to ioremap PCC ACK register
  ");
  			return -ENOMEM;
  		}
  	}
  
  	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;

  	struct acpi_table_pcct *acpi_pcct_tbl;
  	int count, i, rc;
  	int sum = 0;

  	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.
  ");
  		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);

  	sum += (count > 0) ? count : 0;
  
  	count = acpi_table_parse_entries(ACPI_SIG_PCCT,
  			sizeof(struct acpi_table_pcct),
  			ACPI_PCCT_TYPE_HW_REDUCED_SUBSPACE_TYPE2,
  			parse_pcc_subspace, MAX_PCC_SUBSPACES);
  	sum += (count > 0) ? count : 0;

  	if (sum == 0 || sum >= MAX_PCC_SUBSPACES) {

  		pr_err("Error parsing PCC subspaces from PCCT
  ");
  		return -EINVAL;
  	}
  
  	pcc_mbox_channels = kzalloc(sizeof(struct mbox_chan) *

  			sum, GFP_KERNEL);

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

  	pcc_doorbell_vaddr = kcalloc(sum, sizeof(void *), GFP_KERNEL);

  	if (!pcc_doorbell_vaddr) {

  		rc = -ENOMEM;
  		goto err_free_mbox;
  	}
  
  	pcc_doorbell_ack_vaddr = kcalloc(sum, sizeof(void *), GFP_KERNEL);
  	if (!pcc_doorbell_ack_vaddr) {
  		rc = -ENOMEM;
  		goto err_free_db_vaddr;
  	}
  
  	pcc_doorbell_irq = kcalloc(sum, sizeof(int), GFP_KERNEL);
  	if (!pcc_doorbell_irq) {
  		rc = -ENOMEM;
  		goto err_free_db_ack_vaddr;

  	}

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

  	acpi_pcct_tbl = (struct acpi_table_pcct *) pcct_tbl;
  	if (acpi_pcct_tbl->flags & ACPI_PCCT_DOORBELL)
  		pcc_mbox_ctrl.txdone_irq = true;
  
  	for (i = 0; i < sum; i++) {

  		struct acpi_generic_address *db_reg;
  		struct acpi_pcct_hw_reduced *pcct_ss;

  		pcc_mbox_channels[i].con_priv = pcct_entry;

  		pcct_ss = (struct acpi_pcct_hw_reduced *) pcct_entry;
  
  		if (pcc_mbox_ctrl.txdone_irq) {
  			rc = pcc_parse_subspace_irq(i, pcct_ss);
  			if (rc < 0)
  				goto err;
  		}

  		/* If doorbell is in system memory cache the virt address */

  		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 = sum;

  
  	pr_info("Detected %d PCC Subspaces
  ", pcc_mbox_ctrl.num_chans);
  
  	return 0;

  
  err:
  	kfree(pcc_doorbell_irq);
  err_free_db_ack_vaddr:
  	kfree(pcc_doorbell_ack_vaddr);
  err_free_db_vaddr:
  	kfree(pcc_doorbell_vaddr);
  err_free_mbox:
  	kfree(pcc_mbox_channels);
  	return rc;

  }
  
  /**
   * 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
  ");
  	ret = mbox_controller_register(&pcc_mbox_ctrl);
  
  	if (ret) {
  		pr_err("Err registering PCC as Mailbox controller: %d
  ", 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.
  ");

  		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
  ");

  		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);