linux/drivers/mailbox/pcc.c
Ashwin Chaugule d3c68f218f PCC: Initialize PCC Mailbox earlier at boot
This change initializes the PCC Mailbox earlier than
the ACPI processor driver. This enables drivers introduced
in follow up patches (e.g. CPPC) to be probed via the ACPI
processor driver interface. The CPPC probe requires the PCC
channel to be initialized for it to query each CPUs performance
capabilities.

Signed-off-by: Ashwin Chaugule <ashwin.chaugule@linaro.org>
Reviewed-by: Al Stone <al.stone@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
2015-08-25 03:25:46 +02:00

362 lines
9.9 KiB
C

/*
* 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 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;
}
/* 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;
}
/*
* 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);