path: root/drivers/platform/x86/intel_speed_select_if/isst_if_common.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Intel Speed Select Interface: Common functions
 * Copyright (c) 2019, Intel Corporation.
 * All rights reserved.
 *
 * Author: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
 */

#include <linux/cpufeature.h>
#include <linux/cpuhotplug.h>
#include <linux/fs.h>
#include <linux/miscdevice.h>
#include <linux/module.h>
#include <linux/pci.h>
#include <linux/sched/signal.h>
#include <linux/slab.h>
#include <linux/uaccess.h>
#include <uapi/linux/isst_if.h>

#include "isst_if_common.h"

#define MSR_THREAD_ID_INFO	0x53
#define MSR_CPU_BUS_NUMBER	0x128

static struct isst_if_cmd_cb punit_callbacks[ISST_IF_DEV_MAX];

static int isst_if_get_platform_info(void __user *argp)
{
	struct isst_if_platform_info info;

	info.api_version = ISST_IF_API_VERSION,
	info.driver_version = ISST_IF_DRIVER_VERSION,
	info.max_cmds_per_ioctl = ISST_IF_CMD_LIMIT,
	info.mbox_supported = punit_callbacks[ISST_IF_DEV_MBOX].registered;
	info.mmio_supported = punit_callbacks[ISST_IF_DEV_MMIO].registered;

	if (copy_to_user(argp, &info, sizeof(info)))
		return -EFAULT;

	return 0;
}


struct isst_if_cpu_info {
	/* For BUS 0 and BUS 1 only, which we need for PUNIT interface */
	int bus_info[2];
	int punit_cpu_id;
};

static struct isst_if_cpu_info *isst_cpu_info;

/**
 * isst_if_get_pci_dev() - Get the PCI device instance for a CPU
 * @cpu: Logical CPU number.
 * @bus_number: The bus number assigned by the hardware.
 * @dev: The device number assigned by the hardware.
 * @fn: The function number assigned by the hardware.
 *
 * Using cached bus information, find out the PCI device for a bus number,
 * device and function.
 *
 * Return: Return pci_dev pointer or NULL.
 */
struct pci_dev *isst_if_get_pci_dev(int cpu, int bus_no, int dev, int fn)
{
	int bus_number;

	if (bus_no < 0 || bus_no > 1 || cpu < 0 || cpu >= nr_cpu_ids ||
	    cpu >= num_possible_cpus())
		return NULL;

	bus_number = isst_cpu_info[cpu].bus_info[bus_no];
	if (bus_number < 0)
		return NULL;

	return pci_get_domain_bus_and_slot(0, bus_number, PCI_DEVFN(dev, fn));
}
EXPORT_SYMBOL_GPL(isst_if_get_pci_dev);

static int isst_if_cpu_online(unsigned int cpu)
{
	u64 data;
	int ret;

	ret = rdmsrl_safe(MSR_CPU_BUS_NUMBER, &data);
	if (ret) {
		/* This is not a fatal error on MSR mailbox only I/F */
		isst_cpu_info[cpu].bus_info[0] = -1;
		isst_cpu_info[cpu].bus_info[1] = -1;
	} else {
		isst_cpu_info[cpu].bus_info[0] = data & 0xff;
		isst_cpu_info[cpu].bus_info[1] = (data >> 8) & 0xff;
	}

	ret = rdmsrl_safe(MSR_THREAD_ID_INFO, &data);
	if (ret) {
		isst_cpu_info[cpu].punit_cpu_id = -1;
		return ret;
	}
	isst_cpu_info[cpu].punit_cpu_id = data;

	return 0;
}

static int isst_if_online_id;

static int isst_if_cpu_info_init(void)
{
	int ret;

	isst_cpu_info = kcalloc(num_possible_cpus(),
				sizeof(*isst_cpu_info),
				GFP_KERNEL);
	if (!isst_cpu_info)
		return -ENOMEM;

	ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN,
				"platform/x86/isst-if:online",
				isst_if_cpu_online, NULL);
	if (ret < 0) {
		kfree(isst_cpu_info);
		return ret;
	}

	isst_if_online_id = ret;

	return 0;
}

static void isst_if_cpu_info_exit(void)
{
	cpuhp_remove_state(isst_if_online_id);
	kfree(isst_cpu_info);
};

static long isst_if_proc_phyid_req(u8 *cmd_ptr, int *write_only, int resume)
{
	struct isst_if_cpu_map *cpu_map;

	cpu_map = (struct isst_if_cpu_map *)cmd_ptr;
	if (cpu_map->logical_cpu >= nr_cpu_ids ||
	    cpu_map->logical_cpu >= num_possible_cpus())
		return -EINVAL;

	*write_only = 0;
	cpu_map->physical_cpu = isst_cpu_info[cpu_map->logical_cpu].punit_cpu_id;

	return 0;
}

static long isst_if_exec_multi_cmd(void __user *argp, struct isst_if_cmd_cb *cb)
{
	unsigned char __user *ptr;
	u32 cmd_count;
	u8 *cmd_ptr;
	long ret;
	int i;

	/* Each multi command has u32 command count as the first field */
	if (copy_from_user(&cmd_count, argp, sizeof(cmd_count)))
		return -EFAULT;

	if (!cmd_count || cmd_count > ISST_IF_CMD_LIMIT)
		return -EINVAL;

	cmd_ptr = kmalloc(cb->cmd_size, GFP_KERNEL);
	if (!cmd_ptr)
		return -ENOMEM;

	/* cb->offset points to start of the command after the command count */
	ptr = argp + cb->offset;

	for (i = 0; i < cmd_count; ++i) {
		int wr_only;

		if (signal_pending(current)) {
			ret = -EINTR;
			break;
		}

		if (copy_from_user(cmd_ptr, ptr, cb->cmd_size)) {
			ret = -EFAULT;
			break;
		}

		ret = cb->cmd_callback(cmd_ptr, &wr_only, 0);
		if (ret)
			break;

		if (!wr_only && copy_to_user(ptr, cmd_ptr, cb->cmd_size)) {
			ret = -EFAULT;
			break;
		}

		ptr += cb->cmd_size;
	}

	kfree(cmd_ptr);

	return i ? i : ret;
}

static long isst_if_def_ioctl(struct file *file, unsigned int cmd,
			      unsigned long arg)
{
	void __user *argp = (void __user *)arg;
	struct isst_if_cmd_cb cmd_cb;
	long ret = -ENOTTY;

	switch (cmd) {
	case ISST_IF_GET_PLATFORM_INFO:
		ret = isst_if_get_platform_info(argp);
		break;
	case ISST_IF_GET_PHY_ID:
		cmd_cb.cmd_size = sizeof(struct isst_if_cpu_map);
		cmd_cb.offset = offsetof(struct isst_if_cpu_maps, cpu_map);
		cmd_cb.cmd_callback = isst_if_proc_phyid_req;
		ret = isst_if_exec_multi_cmd(argp, &cmd_cb);
		break;
	default:
		break;
	}

	return ret;
}

static DEFINE_MUTEX(punit_misc_dev_lock);
static int misc_usage_count;
static int misc_device_ret;
static int misc_device_open;

static int isst_if_open(struct inode *inode, struct file *file)
{
	int i, ret = 0;

	/* Fail open, if a module is going away */
	mutex_lock(&punit_misc_dev_lock);
	for (i = 0; i < ISST_IF_DEV_MAX; ++i) {
		struct isst_if_cmd_cb *cb = &punit_callbacks[i];

		if (cb->registered && !try_module_get(cb->owner)) {
			ret = -ENODEV;
			break;
		}
	}
	if (ret) {
		int j;

		for (j = 0; j < i; ++j) {
			struct isst_if_cmd_cb *cb;

			cb = &punit_callbacks[j];
			if (cb->registered)
				module_put(cb->owner);
		}
	} else {
		misc_device_open++;
	}
	mutex_unlock(&punit_misc_dev_lock);

	return ret;
}

static int isst_if_relase(struct inode *inode, struct file *f)
{
	int i;

	mutex_lock(&punit_misc_dev_lock);
	misc_device_open--;
	for (i = 0; i < ISST_IF_DEV_MAX; ++i) {
		struct isst_if_cmd_cb *cb = &punit_callbacks[i];

		if (cb->registered)
			module_put(cb->owner);
	}
	mutex_unlock(&punit_misc_dev_lock);

	return 0;
}

static const struct file_operations isst_if_char_driver_ops = {
	.open = isst_if_open,
	.unlocked_ioctl = isst_if_def_ioctl,
	.release = isst_if_relase,
};

static struct miscdevice isst_if_char_driver = {
	.minor		= MISC_DYNAMIC_MINOR,
	.name		= "isst_interface",
	.fops		= &isst_if_char_driver_ops,
};

/**
 * isst_if_cdev_register() - Register callback for IOCTL
 * @device_type: The device type this callback handling.
 * @cb:	Callback structure.
 *
 * This function registers a callback to device type. On very first call
 * it will register a misc device, which is used for user kernel interface.
 * Other calls simply increment ref count. Registry will fail, if the user
 * already opened misc device for operation. Also if the misc device
 * creation failed, then it will not try again and all callers will get
 * failure code.
 *
 * Return: Return the return value from the misc creation device or -EINVAL
 * for unsupported device type.
 */
int isst_if_cdev_register(int device_type, struct isst_if_cmd_cb *cb)
{
	if (misc_device_ret)
		return misc_device_ret;

	if (device_type >= ISST_IF_DEV_MAX)
		return -EINVAL;

	mutex_lock(&punit_misc_dev_lock);
	if (misc_device_open) {
		mutex_unlock(&punit_misc_dev_lock);
		return -EAGAIN;
	}
	if (!misc_usage_count) {
		int ret;

		misc_device_ret = misc_register(&isst_if_char_driver);
		if (misc_device_ret)
			goto unlock_exit;

		ret = isst_if_cpu_info_init();
		if (ret) {
			misc_deregister(&isst_if_char_driver);
			misc_device_ret = ret;
			goto unlock_exit;
		}
	}
	memcpy(&punit_callbacks[device_type], cb, sizeof(*cb));
	punit_callbacks[device_type].registered = 1;
	misc_usage_count++;
unlock_exit:
	mutex_unlock(&punit_misc_dev_lock);

	return misc_device_ret;
}
EXPORT_SYMBOL_GPL(isst_if_cdev_register);

/**
 * isst_if_cdev_unregister() - Unregister callback for IOCTL
 * @device_type: The device type to unregister.
 *
 * This function unregisters the previously registered callback. If this
 * is the last callback unregistering, then misc device is removed.
 *
 * Return: None.
 */
void isst_if_cdev_unregister(int device_type)
{
	mutex_lock(&punit_misc_dev_lock);
	misc_usage_count--;
	punit_callbacks[device_type].registered = 0;
	if (!misc_usage_count && !misc_device_ret) {
		misc_deregister(&isst_if_char_driver);
		isst_if_cpu_info_exit();
	}
	mutex_unlock(&punit_misc_dev_lock);
}
EXPORT_SYMBOL_GPL(isst_if_cdev_unregister);

MODULE_LICENSE("GPL v2");