// SPDX-License-Identifier: GPL-2.0
/*
* Intel Speed Select Interface: Mbox via MSR Interface
* Copyright (c) 2019, Intel Corporation.
* All rights reserved.
*
* Author: Srinivas Pandruvada <[email protected]>
*/
#include <linux/module.h>
#include <linux/cpuhotplug.h>
#include <linux/pci.h>
#include <linux/sched/signal.h>
#include <linux/slab.h>
#include <linux/suspend.h>
#include <linux/topology.h>
#include <linux/uaccess.h>
#include <uapi/linux/isst_if.h>
#include <asm/cpu_device_id.h>
#include <asm/intel-family.h>
#include "isst_if_common.h"
#define MSR_OS_MAILBOX_BUSY_BIT 31
/*
* Based on experiments count is never more than 1, as the MSR overhead
* is enough to finish the command. So here this is the worst case number.
*/
#define OS_MAILBOX_RETRY_COUNT 3
static int isst_if_send_mbox_cmd(u8 command, u8 sub_command, u32 parameter,
u32 command_data, u32 *response_data)
{
u32 retries;
u64 data;
int ret;
/* Poll for rb bit == 0 */
retries = OS_MAILBOX_RETRY_COUNT;
do {
rdmsrl(MSR_OS_MAILBOX_INTERFACE, data);
if (data & BIT_ULL(MSR_OS_MAILBOX_BUSY_BIT)) {
ret = -EBUSY;
continue;
}
ret = 0;
break;
} while (--retries);
if (ret)
return ret;
/* Write DATA register */
wrmsrl(MSR_OS_MAILBOX_DATA, command_data);
/* Write command register */
data = BIT_ULL(MSR_OS_MAILBOX_BUSY_BIT) |
(parameter & GENMASK_ULL(13, 0)) << 16 |
(sub_command << 8) |
command;
wrmsrl(MSR_OS_MAILBOX_INTERFACE, data);
/* Poll for rb bit == 0 */
retries = OS_MAILBOX_RETRY_COUNT;
do {
rdmsrl(MSR_OS_MAILBOX_INTERFACE, data);
if (data & BIT_ULL(MSR_OS_MAILBOX_BUSY_BIT)) {
ret = -EBUSY;
continue;
}
if (data & 0xff)
return -ENXIO;
if (response_data) {
rdmsrl(MSR_OS_MAILBOX_DATA, data);
*response_data = data;
}
ret = 0;
break;
} while (--retries);
return ret;
}
struct msrl_action {
int err;
struct isst_if_mbox_cmd *mbox_cmd;
};
/* revisit, smp_call_function_single should be enough for atomic mailbox! */
static void msrl_update_func(void *info)
{
struct msrl_action *act = info;
act->err = isst_if_send_mbox_cmd(act->mbox_cmd->command,
act->mbox_cmd->sub_command,
act->mbox_cmd->parameter,
act->mbox_cmd->req_data,
&act->mbox_cmd->resp_data);
}
static long isst_if_mbox_proc_cmd(u8 *cmd_ptr, int *write_only, int resume)
{
struct msrl_action action;
int ret;
action.mbox_cmd = (struct isst_if_mbox_cmd *)cmd_ptr;
if (isst_if_mbox_cmd_invalid(action.mbox_cmd))
return -EINVAL;
if (isst_if_mbox_cmd_set_req(action.mbox_cmd) &&
!capable(CAP_SYS_ADMIN))
return -EPERM;
/*
* To complete mailbox command, we need to access two MSRs.
* So we don't want race to complete a mailbox transcation.
* Here smp_call ensures that msrl_update_func() has no race
* and also with wait flag, wait for completion.
* smp_call_function_single is using get_cpu() and put_cpu().
*/
ret = smp_call_function_single(action.mbox_cmd->logical_cpu,
msrl_update_func, &action, 1);
if (ret)
return ret;
if (!action.err && !resume && isst_if_mbox_cmd_set_req(action.mbox_cmd))
action.err = isst_store_cmd(action.mbox_cmd->command,
action.mbox_cmd->sub_command,
action.mbox_cmd->logical_cpu, 1,
action.mbox_cmd->parameter,
action.mbox_cmd->req_data);
*write_only = 0;
return action.err;
}
static int isst_pm_notify(struct notifier_block *nb,
unsigned long mode, void *_unused)
{
switch (mode) {
case PM_POST_HIBERNATION:
case PM_POST_RESTORE:
case PM_POST_SUSPEND:
isst_resume_common();
break;
default:
break;
}
return 0;
}
static struct notifier_block isst_pm_nb = {
.notifier_call = isst_pm_notify,
};
static const struct x86_cpu_id isst_if_cpu_ids[] = {
X86_MATCH_VFM(INTEL_SKYLAKE_X, NULL),
{}
};
MODULE_DEVICE_TABLE(x86cpu, isst_if_cpu_ids);
static int __init isst_if_mbox_init(void)
{
struct isst_if_cmd_cb cb;
const struct x86_cpu_id *id;
u64 data;
int ret;
id = x86_match_cpu(isst_if_cpu_ids);
if (!id)
return -ENODEV;
/* Check presence of mailbox MSRs */
ret = rdmsrl_safe(MSR_OS_MAILBOX_INTERFACE, &data);
if (ret)
return ret;
ret = rdmsrl_safe(MSR_OS_MAILBOX_DATA, &data);
if (ret)
return ret;
memset(&cb, 0, sizeof(cb));
cb.cmd_size = sizeof(struct isst_if_mbox_cmd);
cb.offset = offsetof(struct isst_if_mbox_cmds, mbox_cmd);
cb.cmd_callback = isst_if_mbox_proc_cmd;
cb.owner = THIS_MODULE;
ret = isst_if_cdev_register(ISST_IF_DEV_MBOX, &cb);
if (ret)
return ret;
ret = register_pm_notifier(&isst_pm_nb);
if (ret)
isst_if_cdev_unregister(ISST_IF_DEV_MBOX);
return ret;
}
module_init(isst_if_mbox_init)
static void __exit isst_if_mbox_exit(void)
{
unregister_pm_notifier(&isst_pm_nb);
isst_if_cdev_unregister(ISST_IF_DEV_MBOX);
}
module_exit(isst_if_mbox_exit)
MODULE_LICENSE("GPL v2");
MODULE_DESCRIPTION("Intel speed select interface mailbox driver");
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