1 files changed, 758 insertions, 0 deletions

diff --git a/drivers/mailbox/pcc.c b/drivers/mailbox/pcc.c
new file mode 100644
index 000000000..105d46c98
--- /dev/null
+++ b/drivers/mailbox/pcc.c
@@ -0,0 +1,758 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *	Copyright (C) 2014 Linaro Ltd.
+ *	Author:	Ashwin Chaugule <ashwin.chaugule@linaro.org>
+ *
+ *  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 succeeded 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/log2.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 MBOX_IRQ_NAME		"pcc-mbox"
+
+/**
+ * struct pcc_chan_reg - PCC register bundle
+ *
+ * @vaddr: cached virtual address for this register
+ * @gas: pointer to the generic address structure for this register
+ * @preserve_mask: bitmask to preserve when writing to this register
+ * @set_mask: bitmask to set when writing to this register
+ * @status_mask: bitmask to determine and/or update the status for this register
+ */
+struct pcc_chan_reg {
+	void __iomem *vaddr;
+	struct acpi_generic_address *gas;
+	u64 preserve_mask;
+	u64 set_mask;
+	u64 status_mask;
+};
+
+/**
+ * struct pcc_chan_info - PCC channel specific information
+ *
+ * @chan: PCC channel information with Shared Memory Region info
+ * @db: PCC register bundle for the doorbell register
+ * @plat_irq_ack: PCC register bundle for the platform interrupt acknowledge
+ *	register
+ * @cmd_complete: PCC register bundle for the command complete check register
+ * @cmd_update: PCC register bundle for the command complete update register
+ * @error: PCC register bundle for the error status register
+ * @plat_irq: platform interrupt
+ */
+struct pcc_chan_info {
+	struct pcc_mbox_chan chan;
+	struct pcc_chan_reg db;
+	struct pcc_chan_reg plat_irq_ack;
+	struct pcc_chan_reg cmd_complete;
+	struct pcc_chan_reg cmd_update;
+	struct pcc_chan_reg error;
+	int plat_irq;
+};
+
+#define to_pcc_chan_info(c) container_of(c, struct pcc_chan_info, chan)
+static struct pcc_chan_info *chan_info;
+static int pcc_chan_count;
+
+/*
+ * 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 void read_register(void __iomem *vaddr, u64 *val, unsigned int bit_width)
+{
+	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;
+	}
+}
+
+static void write_register(void __iomem *vaddr, u64 val, unsigned int bit_width)
+{
+	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;
+	}
+}
+
+static int pcc_chan_reg_read(struct pcc_chan_reg *reg, u64 *val)
+{
+	int ret = 0;
+
+	if (!reg->gas) {
+		*val = 0;
+		return 0;
+	}
+
+	if (reg->vaddr)
+		read_register(reg->vaddr, val, reg->gas->bit_width);
+	else
+		ret = acpi_read(val, reg->gas);
+
+	return ret;
+}
+
+static int pcc_chan_reg_write(struct pcc_chan_reg *reg, u64 val)
+{
+	int ret = 0;
+
+	if (!reg->gas)
+		return 0;
+
+	if (reg->vaddr)
+		write_register(reg->vaddr, val, reg->gas->bit_width);
+	else
+		ret = acpi_write(val, reg->gas);
+
+	return ret;
+}
+
+static int pcc_chan_reg_read_modify_write(struct pcc_chan_reg *reg)
+{
+	int ret = 0;
+	u64 val;
+
+	ret = pcc_chan_reg_read(reg, &val);
+	if (ret)
+		return ret;
+
+	val &= reg->preserve_mask;
+	val |= reg->set_mask;
+
+	return pcc_chan_reg_write(reg, 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
+ * @irq:	interrupt number
+ * @p: data/cookie passed from the caller to identify the channel
+ *
+ * Returns: IRQ_HANDLED if interrupt is handled or IRQ_NONE if not
+ */
+static irqreturn_t pcc_mbox_irq(int irq, void *p)
+{
+	struct pcc_chan_info *pchan;
+	struct mbox_chan *chan = p;
+	u64 val;
+	int ret;
+
+	pchan = chan->con_priv;
+
+	ret = pcc_chan_reg_read(&pchan->cmd_complete, &val);
+	if (ret)
+		return IRQ_NONE;
+
+	if (val) { /* Ensure GAS exists and value is non-zero */
+		val &= pchan->cmd_complete.status_mask;
+		if (!val)
+			return IRQ_NONE;
+	}
+
+	ret = pcc_chan_reg_read(&pchan->error, &val);
+	if (ret)
+		return IRQ_NONE;
+	val &= pchan->error.status_mask;
+	if (val) {
+		val &= ~pchan->error.status_mask;
+		pcc_chan_reg_write(&pchan->error, val);
+		return IRQ_NONE;
+	}
+
+	if (pcc_chan_reg_read_modify_write(&pchan->plat_irq_ack))
+		return IRQ_NONE;
+
+	mbox_chan_received_data(chan, NULL);
+
+	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 PCC Mailbox Channel if successful or ERR_PTR.
+ */
+struct pcc_mbox_chan *
+pcc_mbox_request_channel(struct mbox_client *cl, int subspace_id)
+{
+	struct pcc_chan_info *pchan;
+	struct mbox_chan *chan;
+	struct device *dev;
+	unsigned long flags;
+
+	if (subspace_id < 0 || subspace_id >= pcc_chan_count)
+		return ERR_PTR(-ENOENT);
+
+	pchan = chan_info + subspace_id;
+	chan = pchan->chan.mchan;
+	if (IS_ERR(chan) || chan->cl) {
+		pr_err("Channel not found for idx: %d\n", subspace_id);
+		return ERR_PTR(-EBUSY);
+	}
+	dev = chan->mbox->dev;
+
+	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 (pchan->plat_irq > 0) {
+		int rc;
+
+		rc = devm_request_irq(dev, pchan->plat_irq, pcc_mbox_irq, 0,
+				      MBOX_IRQ_NAME, chan);
+		if (unlikely(rc)) {
+			dev_err(dev, "failed to register PCC interrupt %d\n",
+				pchan->plat_irq);
+			pcc_mbox_free_channel(&pchan->chan);
+			return ERR_PTR(rc);
+		}
+	}
+
+	return &pchan->chan;
+}
+EXPORT_SYMBOL_GPL(pcc_mbox_request_channel);
+
+/**
+ * pcc_mbox_free_channel - Clients call this to free their Channel.
+ *
+ * @pchan: Pointer to the PCC mailbox channel as returned by
+ *	   pcc_mbox_request_channel()
+ */
+void pcc_mbox_free_channel(struct pcc_mbox_chan *pchan)
+{
+	struct pcc_chan_info *pchan_info = to_pcc_chan_info(pchan);
+	struct mbox_chan *chan = pchan->mchan;
+	unsigned long flags;
+
+	if (!chan || !chan->cl)
+		return;
+
+	if (pchan_info->plat_irq > 0)
+		devm_free_irq(chan->mbox->dev, pchan_info->plat_irq, chan);
+
+	spin_lock_irqsave(&chan->lock, flags);
+	chan->cl = NULL;
+	chan->active_req = NULL;
+	if (chan->txdone_method == 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)
+{
+	int ret;
+	struct pcc_chan_info *pchan = chan->con_priv;
+
+	ret = pcc_chan_reg_read_modify_write(&pchan->cmd_update);
+	if (ret)
+		return ret;
+
+	return pcc_chan_reg_read_modify_write(&pchan->db);
+}
+
+static const struct mbox_chan_ops pcc_chan_ops = {
+	.send_data = pcc_send_data,
+};
+
+/**
+ * parse_pcc_subspace - Count PCC subspaces defined
+ * @header: Pointer to the ACPI subtable header under the PCCT.
+ * @end: End of subtable entry.
+ *
+ * Return: If we find a PCC subspace entry of a valid type, return 0.
+ *	Otherwise, return -EINVAL.
+ *
+ * This gets called for each entry in the PCC table.
+ */
+static int parse_pcc_subspace(union acpi_subtable_headers *header,
+		const unsigned long end)
+{
+	struct acpi_pcct_subspace *ss = (struct acpi_pcct_subspace *) header;
+
+	if (ss->header.type < ACPI_PCCT_TYPE_RESERVED)
+		return 0;
+
+	return -EINVAL;
+}
+
+static int
+pcc_chan_reg_init(struct pcc_chan_reg *reg, struct acpi_generic_address *gas,
+		  u64 preserve_mask, u64 set_mask, u64 status_mask, char *name)
+{
+	if (gas->space_id == ACPI_ADR_SPACE_SYSTEM_MEMORY) {
+		if (!(gas->bit_width >= 8 && gas->bit_width <= 64 &&
+		      is_power_of_2(gas->bit_width))) {
+			pr_err("Error: Cannot access register of %u bit width",
+			       gas->bit_width);
+			return -EFAULT;
+		}
+
+		reg->vaddr = acpi_os_ioremap(gas->address, gas->bit_width / 8);
+		if (!reg->vaddr) {
+			pr_err("Failed to ioremap PCC %s register\n", name);
+			return -ENOMEM;
+		}
+	}
+	reg->gas = gas;
+	reg->preserve_mask = preserve_mask;
+	reg->set_mask = set_mask;
+	reg->status_mask = status_mask;
+	return 0;
+}
+
+/**
+ * pcc_parse_subspace_irq - Parse the PCC IRQ and PCC ACK register
+ *
+ * @pchan: Pointer to the PCC channel info structure.
+ * @pcct_entry: Pointer to the ACPI subtable header.
+ *
+ * Return: 0 for Success, else errno.
+ *
+ * There should be one entry per PCC channel. This gets called for each
+ * entry in the PCC table. This uses PCCY Type1 structure for all applicable
+ * types(Type 1-4) to fetch irq
+ */
+static int pcc_parse_subspace_irq(struct pcc_chan_info *pchan,
+				  struct acpi_subtable_header *pcct_entry)
+{
+	int ret = 0;
+	struct acpi_pcct_hw_reduced *pcct_ss;
+
+	if (pcct_entry->type < ACPI_PCCT_TYPE_HW_REDUCED_SUBSPACE ||
+	    pcct_entry->type > ACPI_PCCT_TYPE_EXT_PCC_SLAVE_SUBSPACE)
+		return 0;
+
+	pcct_ss = (struct acpi_pcct_hw_reduced *)pcct_entry;
+	pchan->plat_irq = pcc_map_interrupt(pcct_ss->platform_interrupt,
+					    (u32)pcct_ss->flags);
+	if (pchan->plat_irq <= 0) {
+		pr_err("PCC GSI %d not registered\n",
+		       pcct_ss->platform_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;
+
+		ret = pcc_chan_reg_init(&pchan->plat_irq_ack,
+					&pcct2_ss->platform_ack_register,
+					pcct2_ss->ack_preserve_mask,
+					pcct2_ss->ack_write_mask, 0,
+					"PLAT IRQ ACK");
+
+	} else if (pcct_ss->header.type == ACPI_PCCT_TYPE_EXT_PCC_MASTER_SUBSPACE ||
+		   pcct_ss->header.type == ACPI_PCCT_TYPE_EXT_PCC_SLAVE_SUBSPACE) {
+		struct acpi_pcct_ext_pcc_master *pcct_ext = (void *)pcct_ss;
+
+		ret = pcc_chan_reg_init(&pchan->plat_irq_ack,
+					&pcct_ext->platform_ack_register,
+					pcct_ext->ack_preserve_mask,
+					pcct_ext->ack_set_mask, 0,
+					"PLAT IRQ ACK");
+	}
+
+	return ret;
+}
+
+/**
+ * pcc_parse_subspace_db_reg - Parse the PCC doorbell register
+ *
+ * @pchan: Pointer to the PCC channel info structure.
+ * @pcct_entry: Pointer to the ACPI subtable header.
+ *
+ * Return: 0 for Success, else errno.
+ */
+static int pcc_parse_subspace_db_reg(struct pcc_chan_info *pchan,
+				     struct acpi_subtable_header *pcct_entry)
+{
+	int ret = 0;
+
+	if (pcct_entry->type <= ACPI_PCCT_TYPE_HW_REDUCED_SUBSPACE_TYPE2) {
+		struct acpi_pcct_subspace *pcct_ss;
+
+		pcct_ss = (struct acpi_pcct_subspace *)pcct_entry;
+
+		ret = pcc_chan_reg_init(&pchan->db,
+					&pcct_ss->doorbell_register,
+					pcct_ss->preserve_mask,
+					pcct_ss->write_mask, 0,	"Doorbell");
+
+	} else {
+		struct acpi_pcct_ext_pcc_master *pcct_ext;
+
+		pcct_ext = (struct acpi_pcct_ext_pcc_master *)pcct_entry;
+
+		ret = pcc_chan_reg_init(&pchan->db,
+					&pcct_ext->doorbell_register,
+					pcct_ext->preserve_mask,
+					pcct_ext->write_mask, 0, "Doorbell");
+		if (ret)
+			return ret;
+
+		ret = pcc_chan_reg_init(&pchan->cmd_complete,
+					&pcct_ext->cmd_complete_register,
+					0, 0, pcct_ext->cmd_complete_mask,
+					"Command Complete Check");
+		if (ret)
+			return ret;
+
+		ret = pcc_chan_reg_init(&pchan->cmd_update,
+					&pcct_ext->cmd_update_register,
+					pcct_ext->cmd_update_preserve_mask,
+					pcct_ext->cmd_update_set_mask, 0,
+					"Command Complete Update");
+		if (ret)
+			return ret;
+
+		ret = pcc_chan_reg_init(&pchan->error,
+					&pcct_ext->error_status_register,
+					0, 0, pcct_ext->error_status_mask,
+					"Error Status");
+	}
+	return ret;
+}
+
+/**
+ * pcc_parse_subspace_shmem - Parse the PCC Shared Memory Region information
+ *
+ * @pchan: Pointer to the PCC channel info structure.
+ * @pcct_entry: Pointer to the ACPI subtable header.
+ *
+ */
+static void pcc_parse_subspace_shmem(struct pcc_chan_info *pchan,
+				     struct acpi_subtable_header *pcct_entry)
+{
+	if (pcct_entry->type <= ACPI_PCCT_TYPE_HW_REDUCED_SUBSPACE_TYPE2) {
+		struct acpi_pcct_subspace *pcct_ss =
+			(struct acpi_pcct_subspace *)pcct_entry;
+
+		pchan->chan.shmem_base_addr = pcct_ss->base_address;
+		pchan->chan.shmem_size = pcct_ss->length;
+		pchan->chan.latency = pcct_ss->latency;
+		pchan->chan.max_access_rate = pcct_ss->max_access_rate;
+		pchan->chan.min_turnaround_time = pcct_ss->min_turnaround_time;
+	} else {
+		struct acpi_pcct_ext_pcc_master *pcct_ext =
+			(struct acpi_pcct_ext_pcc_master *)pcct_entry;
+
+		pchan->chan.shmem_base_addr = pcct_ext->base_address;
+		pchan->chan.shmem_size = pcct_ext->length;
+		pchan->chan.latency = pcct_ext->latency;
+		pchan->chan.max_access_rate = pcct_ext->max_access_rate;
+		pchan->chan.min_turnaround_time = pcct_ext->min_turnaround_time;
+	}
+}
+
+/**
+ * acpi_pcc_probe - Parse the ACPI tree for the PCCT.
+ *
+ * Return: 0 for Success, else errno.
+ */
+static int __init acpi_pcc_probe(void)
+{
+	int count, i, rc = 0;
+	acpi_status status;
+	struct acpi_table_header *pcct_tbl;
+	struct acpi_subtable_proc proc[ACPI_PCCT_TYPE_RESERVED];
+
+	status = acpi_get_table(ACPI_SIG_PCCT, 0, &pcct_tbl);
+	if (ACPI_FAILURE(status) || !pcct_tbl)
+		return -ENODEV;
+
+	/* Set up the subtable handlers */
+	for (i = ACPI_PCCT_TYPE_GENERIC_SUBSPACE;
+	     i < ACPI_PCCT_TYPE_RESERVED; i++) {
+		proc[i].id = i;
+		proc[i].count = 0;
+		proc[i].handler = parse_pcc_subspace;
+	}
+
+	count = acpi_table_parse_entries_array(ACPI_SIG_PCCT,
+			sizeof(struct acpi_table_pcct), proc,
+			ACPI_PCCT_TYPE_RESERVED, MAX_PCC_SUBSPACES);
+	if (count <= 0 || count > MAX_PCC_SUBSPACES) {
+		if (count < 0)
+			pr_warn("Error parsing PCC subspaces from PCCT\n");
+		else
+			pr_warn("Invalid PCCT: %d PCC subspaces\n", count);
+
+		rc = -EINVAL;
+	} else {
+		pcc_chan_count = count;
+	}
+
+	acpi_put_table(pcct_tbl);
+
+	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)
+{
+	struct device *dev = &pdev->dev;
+	struct mbox_controller *pcc_mbox_ctrl;
+	struct mbox_chan *pcc_mbox_channels;
+	struct acpi_table_header *pcct_tbl;
+	struct acpi_subtable_header *pcct_entry;
+	struct acpi_table_pcct *acpi_pcct_tbl;
+	acpi_status status = AE_OK;
+	int i, rc, count = pcc_chan_count;
+
+	/* Search for PCCT */
+	status = acpi_get_table(ACPI_SIG_PCCT, 0, &pcct_tbl);
+
+	if (ACPI_FAILURE(status) || !pcct_tbl)
+		return -ENODEV;
+
+	pcc_mbox_channels = devm_kcalloc(dev, count, sizeof(*pcc_mbox_channels),
+					 GFP_KERNEL);
+	if (!pcc_mbox_channels) {
+		rc = -ENOMEM;
+		goto err;
+	}
+
+	chan_info = devm_kcalloc(dev, count, sizeof(*chan_info), GFP_KERNEL);
+	if (!chan_info) {
+		rc = -ENOMEM;
+		goto err;
+	}
+
+	pcc_mbox_ctrl = devm_kzalloc(dev, sizeof(*pcc_mbox_ctrl), GFP_KERNEL);
+	if (!pcc_mbox_ctrl) {
+		rc = -ENOMEM;
+		goto err;
+	}
+
+	/* 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 < count; i++) {
+		struct pcc_chan_info *pchan = chan_info + i;
+
+		pcc_mbox_channels[i].con_priv = pchan;
+		pchan->chan.mchan = &pcc_mbox_channels[i];
+
+		if (pcct_entry->type == ACPI_PCCT_TYPE_EXT_PCC_SLAVE_SUBSPACE &&
+		    !pcc_mbox_ctrl->txdone_irq) {
+			pr_err("Platform Interrupt flag must be set to 1");
+			rc = -EINVAL;
+			goto err;
+		}
+
+		if (pcc_mbox_ctrl->txdone_irq) {
+			rc = pcc_parse_subspace_irq(pchan, pcct_entry);
+			if (rc < 0)
+				goto err;
+		}
+		rc = pcc_parse_subspace_db_reg(pchan, pcct_entry);
+		if (rc < 0)
+			goto err;
+
+		pcc_parse_subspace_shmem(pchan, pcct_entry);
+
+		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);
+
+	pcc_mbox_ctrl->chans = pcc_mbox_channels;
+	pcc_mbox_ctrl->ops = &pcc_chan_ops;
+	pcc_mbox_ctrl->dev = dev;
+
+	pr_info("Registering PCC driver as Mailbox controller\n");
+	rc = mbox_controller_register(pcc_mbox_ctrl);
+	if (rc)
+		pr_err("Err registering PCC as Mailbox controller: %d\n", rc);
+	else
+		return 0;
+err:
+	acpi_put_table(pcct_tbl);
+	return rc;
+}
+
+static struct platform_driver pcc_mbox_driver = {
+	.probe = pcc_mbox_probe,
+	.driver = {
+		.name = "PCCT",
+	},
+};
+
+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");
+		pcc_chan_count = 0;
+		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);