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/*
* 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 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->platform_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\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);
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\n",
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 =
|