--- /dev/null
+/*
+ * 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 "mailbox.h"
+
+#define MAX_PCC_SUBSPACES 256
+
+static struct mbox_chan *pcc_mbox_channels;
+
+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)
+{
+ struct mbox_chan *pcc_chan;
+
+ if (id < 0 || id > pcc_mbox_ctrl.num_chans)
+ return ERR_PTR(-ENOENT);
+
+ pcc_chan = (struct mbox_chan *)
+ (unsigned long) pcc_mbox_channels +
+ (id * sizeof(*pcc_chan));
+
+ return pcc_chan;
+}
+
+/**
+ * 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 (!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_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;
+
+ doorbell = pcct_ss->doorbell_register;
+ doorbell_preserve = pcct_ss->preserve_mask;
+ doorbell_write = pcct_ss->write_mask;
+
+ /* Sync notification from OS to Platform. */
+ acpi_read(&doorbell_val, &doorbell);
+ acpi_write((doorbell_val & doorbell_preserve) | doorbell_write,
+ &doorbell);
+
+ return 0;
+}
+
+static 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;
+ }
+
+ /* 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++) {
+ pcc_mbox_channels[i].con_priv = 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);
+
+ 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;
+}
+device_initcall(pcc_init);
Code Review / kvmfornfv.git / blobdiff