// SPDX-License-Identifier: GPL-2.0-only
/*
 *  dcdbas.c: Dell Systems Management Base Driver
 *
 *  The Dell Systems Management Base Driver provides a sysfs interface for
 *  systems management software to perform System Management Interrupts (SMIs)
 *  and Host Control Actions (power cycle or power off after OS shutdown) on
 *  Dell systems.
 *
 *  See Documentation/userspace-api/dcdbas.rst for more information.
 *
 *  Copyright (C) 1995-2006 Dell Inc.
 */

#include <linux/platform_device.h>
#include <linux/acpi.h>
#include <linux/dma-mapping.h>
#include <linux/dmi.h>
#include <linux/errno.h>
#include <linux/cpu.h>
#include <linux/gfp.h>
#include <linux/init.h>
#include <linux/io.h>
#include <linux/kernel.h>
#include <linux/mc146818rtc.h>
#include <linux/module.h>
#include <linux/reboot.h>
#include <linux/sched.h>
#include <linux/smp.h>
#include <linux/spinlock.h>
#include <linux/string.h>
#include <linux/sysfs.h>
#include <linux/types.h>
#include <linux/mutex.h>

#include "dcdbas.h"

#define DRIVER_NAME             "dcdbas"
#define DRIVER_VERSION          "5.6.0-3.4"
#define DRIVER_DESCRIPTION      "Dell Systems Management Base Driver"

static struct platform_device *dcdbas_pdev;

static unsigned long max_smi_data_buf_size = MAX_SMI_DATA_BUF_SIZE;
static DEFINE_MUTEX(smi_data_lock);
static u8 *bios_buffer;
static struct smi_buffer smi_buf;

static unsigned int host_control_action;
static unsigned int host_control_smi_type;
static unsigned int host_control_on_shutdown;

static bool wsmt_enabled;

int dcdbas_smi_alloc(struct smi_buffer *smi_buffer, unsigned long size)
{
        smi_buffer->virt = dma_alloc_coherent(&dcdbas_pdev->dev, size,
                                              &smi_buffer->dma, GFP_KERNEL);
        if (!smi_buffer->virt) {
                dev_dbg(&dcdbas_pdev->dev,
                        "%s: failed to allocate memory size %lu\n",
                        __func__, size);
                return -ENOMEM;
        }
        smi_buffer->size = size;

        dev_dbg(&dcdbas_pdev->dev, "%s: phys: %x size: %lu\n",
                __func__, (u32)smi_buffer->dma, smi_buffer->size);

        return 0;
}
EXPORT_SYMBOL_GPL(dcdbas_smi_alloc);

void dcdbas_smi_free(struct smi_buffer *smi_buffer)
{
        if (!smi_buffer->virt)
                return;

        dev_dbg(&dcdbas_pdev->dev, "%s: phys: %x size: %lu\n",
                __func__, (u32)smi_buffer->dma, smi_buffer->size);
        dma_free_coherent(&dcdbas_pdev->dev, smi_buffer->size,
                          smi_buffer->virt, smi_buffer->dma);
        smi_buffer->virt = NULL;
        smi_buffer->dma = 0;
        smi_buffer->size = 0;
}
EXPORT_SYMBOL_GPL(dcdbas_smi_free);

/**
 * smi_data_buf_free: free SMI data buffer
 */
static void smi_data_buf_free(void)
{
        if (!smi_buf.virt || wsmt_enabled)
                return;

        dcdbas_smi_free(&smi_buf);
}

/**
 * smi_data_buf_realloc: grow SMI data buffer if needed
 */
static int smi_data_buf_realloc(unsigned long size)
{
        struct smi_buffer tmp;
        int ret;

        if (smi_buf.size >= size)
                return 0;

        if (size > max_smi_data_buf_size)
                return -EINVAL;

        /* new buffer is needed */
        ret = dcdbas_smi_alloc(&tmp, size);
        if (ret)
                return ret;

        /* memory zeroed by dma_alloc_coherent */
        if (smi_buf.virt)
                memcpy(tmp.virt, smi_buf.virt, smi_buf.size);

        /* free any existing buffer */
        smi_data_buf_free();

        /* set up new buffer for use */
        smi_buf = tmp;

        return 0;
}

static ssize_t smi_data_buf_phys_addr_show(struct device *dev,
                                           struct device_attribute *attr,
                                           char *buf)
{
        return sysfs_emit(buf, "%x\n", (u32)smi_buf.dma);
}

static ssize_t smi_data_buf_size_show(struct device *dev,
                                      struct device_attribute *attr,
                                      char *buf)
{
        return sysfs_emit(buf, "%lu\n", smi_buf.size);
}

static ssize_t smi_data_buf_size_store(struct device *dev,
                                       struct device_attribute *attr,
                                       const char *buf, size_t count)
{
        unsigned long buf_size;
        ssize_t ret;

        buf_size = simple_strtoul(buf, NULL, 10);

        /* make sure SMI data buffer is at least buf_size */
        mutex_lock(&smi_data_lock);
        ret = smi_data_buf_realloc(buf_size);
        mutex_unlock(&smi_data_lock);
        if (ret)
                return ret;

        return count;
}

static ssize_t smi_data_read(struct file *filp, struct kobject *kobj,
                             const struct bin_attribute *bin_attr,
                             char *buf, loff_t pos, size_t count)
{
        ssize_t ret;

        mutex_lock(&smi_data_lock);
        ret = memory_read_from_buffer(buf, count, &pos, smi_buf.virt,
                                        smi_buf.size);
        mutex_unlock(&smi_data_lock);
        return ret;
}

static ssize_t smi_data_write(struct file *filp, struct kobject *kobj,
                              const struct bin_attribute *bin_attr,
                              char *buf, loff_t pos, size_t count)
{
        ssize_t ret;

        if ((pos + count) > max_smi_data_buf_size)
                return -EINVAL;

        mutex_lock(&smi_data_lock);

        ret = smi_data_buf_realloc(pos + count);
        if (ret)
                goto out;

        memcpy(smi_buf.virt + pos, buf, count);
        ret = count;
out:
        mutex_unlock(&smi_data_lock);
        return ret;
}

static ssize_t host_control_action_show(struct device *dev,
                                        struct device_attribute *attr,
                                        char *buf)
{
        return sysfs_emit(buf, "%u\n", host_control_action);
}

static ssize_t host_control_action_store(struct device *dev,
                                         struct device_attribute *attr,
                                         const char *buf, size_t count)
{
        ssize_t ret;

        /* make sure buffer is available for host control command */
        mutex_lock(&smi_data_lock);
        ret = smi_data_buf_realloc(sizeof(struct apm_cmd));
        mutex_unlock(&smi_data_lock);
        if (ret)
                return ret;

        host_control_action = simple_strtoul(buf, NULL, 10);
        return count;
}

static ssize_t host_control_smi_type_show(struct device *dev,
                                          struct device_attribute *attr,
                                          char *buf)
{
        return sysfs_emit(buf, "%u\n", host_control_smi_type);
}

static ssize_t host_control_smi_type_store(struct device *dev,
                                           struct device_attribute *attr,
                                           const char *buf, size_t count)
{
        host_control_smi_type = simple_strtoul(buf, NULL, 10);
        return count;
}

static ssize_t host_control_on_shutdown_show(struct device *dev,
                                             struct device_attribute *attr,
                                             char *buf)
{
        return sysfs_emit(buf, "%u\n", host_control_on_shutdown);
}

static ssize_t host_control_on_shutdown_store(struct device *dev,
                                              struct device_attribute *attr,
                                              const char *buf, size_t count)
{
        host_control_on_shutdown = simple_strtoul(buf, NULL, 10);
        return count;
}

static int raise_smi(void *par)
{
        struct smi_cmd *smi_cmd = par;

        if (smp_processor_id() != 0) {
                dev_dbg(&dcdbas_pdev->dev, "%s: failed to get CPU 0\n",
                        __func__);
                return -EBUSY;
        }

        /* generate SMI */
        /* inb to force posted write through and make SMI happen now */
        asm volatile (
                "outb %b0,%w1\n"
                "inb %w1"
                : /* no output args */
                : "a" (smi_cmd->command_code),
                  "d" (smi_cmd->command_address),
                  "b" (smi_cmd->ebx),
                  "c" (smi_cmd->ecx)
                : "memory"
        );

        return 0;
}
/**
 * dcdbas_smi_request: generate SMI request
 *
 * Called with smi_data_lock.
 */
int dcdbas_smi_request(struct smi_cmd *smi_cmd)
{
        int ret;

        if (smi_cmd->magic != SMI_CMD_MAGIC) {
                dev_info(&dcdbas_pdev->dev, "%s: invalid magic value\n",
                         __func__);
                return -EBADR;
        }

        /* SMI requires CPU 0 */
        cpus_read_lock();
        ret = smp_call_on_cpu(0, raise_smi, smi_cmd, true);
        cpus_read_unlock();

        return ret;
}
EXPORT_SYMBOL(dcdbas_smi_request);

/**
 * smi_request_store:
 *
 * The valid values are:
 * 0: zero SMI data buffer
 * 1: generate calling interface SMI
 * 2: generate raw SMI
 *
 * User application writes smi_cmd to smi_data before telling driver
 * to generate SMI.
 */
static ssize_t smi_request_store(struct device *dev,
                                 struct device_attribute *attr,
                                 const char *buf, size_t count)
{
        struct smi_cmd *smi_cmd;
        unsigned long val = simple_strtoul(buf, NULL, 10);
        ssize_t ret;

        mutex_lock(&smi_data_lock);

        if (smi_buf.size < sizeof(struct smi_cmd)) {
                ret = -ENODEV;
                goto out;
        }
        smi_cmd = (struct smi_cmd *)smi_buf.virt;

        switch (val) {
        case 2:
                /* Raw SMI */
                ret = dcdbas_smi_request(smi_cmd);
                if (!ret)
                        ret = count;
                break;
        case 1:
                /*
                 * Calling Interface SMI
                 *
                 * Provide physical address of command buffer field within
                 * the struct smi_cmd to BIOS.
                 *
                 * Because the address that smi_cmd (smi_buf.virt) points to
                 * will be from memremap() of a non-memory address if WSMT
                 * is present, we can't use virt_to_phys() on smi_cmd, so
                 * we have to use the physical address that was saved when
                 * the virtual address for smi_cmd was received.
                 */
                smi_cmd->ebx = (u32)smi_buf.dma +
                                offsetof(struct smi_cmd, command_buffer);
                ret = dcdbas_smi_request(smi_cmd);
                if (!ret)
                        ret = count;
                break;
        case 0:
                memset(smi_buf.virt, 0, smi_buf.size);
                ret = count;
                break;
        default:
                ret = -EINVAL;
                break;
        }

out:
        mutex_unlock(&smi_data_lock);
        return ret;
}

/**
 * host_control_smi: generate host control SMI
 *
 * Caller must set up the host control command in smi_buf.virt.
 */
static int host_control_smi(void)
{
        struct apm_cmd *apm_cmd;
        u8 *data;
        unsigned long flags;
        u32 num_ticks;
        s8 cmd_status;
        u8 index;

        apm_cmd = (struct apm_cmd *)smi_buf.virt;
        apm_cmd->status = ESM_STATUS_CMD_UNSUCCESSFUL;

        switch (host_control_smi_type) {
        case HC_SMITYPE_TYPE1:
                spin_lock_irqsave(&rtc_lock, flags);
                /* write SMI data buffer physical address */
                data = (u8 *)&smi_buf.dma;
                for (index = PE1300_CMOS_CMD_STRUCT_PTR;
                     index < (PE1300_CMOS_CMD_STRUCT_PTR + 4);
                     index++, data++) {
                        outb(index,
                             (CMOS_BASE_PORT + CMOS_PAGE2_INDEX_PORT_PIIX4));
                        outb(*data,
                             (CMOS_BASE_PORT + CMOS_PAGE2_DATA_PORT_PIIX4));
                }

                /* first set status to -1 as called by spec */
                cmd_status = ESM_STATUS_CMD_UNSUCCESSFUL;
                outb((u8) cmd_status, PCAT_APM_STATUS_PORT);

                /* generate SMM call */
                outb(ESM_APM_CMD, PCAT_APM_CONTROL_PORT);
                spin_unlock_irqrestore(&rtc_lock, flags);

                /* wait a few to see if it executed */
                num_ticks = TIMEOUT_USEC_SHORT_SEMA_BLOCKING;
                while ((s8)inb(PCAT_APM_STATUS_PORT) == ESM_STATUS_CMD_UNSUCCESSFUL) {
                        num_ticks--;
                        if (num_ticks == EXPIRED_TIMER)
                                return -ETIME;
                }
                break;

        case HC_SMITYPE_TYPE2:
        case HC_SMITYPE_TYPE3:
                spin_lock_irqsave(&rtc_lock, flags);
                /* write SMI data buffer physical address */
                data = (u8 *)&smi_buf.dma;
                for (index = PE1400_CMOS_CMD_STRUCT_PTR;
                     index < (PE1400_CMOS_CMD_STRUCT_PTR + 4);
                     index++, data++) {
                        outb(index, (CMOS_BASE_PORT + CMOS_PAGE1_INDEX_PORT));
                        outb(*data, (CMOS_BASE_PORT + CMOS_PAGE1_DATA_PORT));
                }

                /* generate SMM call */
                if (host_control_smi_type == HC_SMITYPE_TYPE3)
                        outb(ESM_APM_CMD, PCAT_APM_CONTROL_PORT);
                else
                        outb(ESM_APM_CMD, PE1400_APM_CONTROL_PORT);

                /* restore RTC index pointer since it was written to above */
                CMOS_READ(RTC_REG_C);
                spin_unlock_irqrestore(&rtc_lock, flags);

                /* read control port back to serialize write */
                cmd_status = inb(PE1400_APM_CONTROL_PORT);

                /* wait a few to see if it executed */
                num_ticks = TIMEOUT_USEC_SHORT_SEMA_BLOCKING;
                while (apm_cmd->status == ESM_STATUS_CMD_UNSUCCESSFUL) {
                        num_ticks--;
                        if (num_ticks == EXPIRED_TIMER)
                                return -ETIME;
                }
                break;

        default:
                dev_dbg(&dcdbas_pdev->dev, "%s: invalid SMI type %u\n",
                        __func__, host_control_smi_type);
                return -ENOSYS;
        }

        return 0;
}

/**
 * dcdbas_host_control: initiate host control
 *
 * This function is called by the driver after the system has
 * finished shutting down if the user application specified a
 * host control action to perform on shutdown.  It is safe to
 * use smi_buf.virt at this point because the system has finished
 * shutting down and no userspace apps are running.
 */
static void dcdbas_host_control(void)
{
        struct apm_cmd *apm_cmd;
        u8 action;

        if (host_control_action == HC_ACTION_NONE)
                return;

        action = host_control_action;
        host_control_action = HC_ACTION_NONE;

        if (!smi_buf.virt) {
                dev_dbg(&dcdbas_pdev->dev, "%s: no SMI buffer\n", __func__);
                return;
        }

        if (smi_buf.size < sizeof(struct apm_cmd)) {
                dev_dbg(&dcdbas_pdev->dev, "%s: SMI buffer too small\n",
                        __func__);
                return;
        }

        apm_cmd = (struct apm_cmd *)smi_buf.virt;

        /* power off takes precedence */
        if (action & HC_ACTION_HOST_CONTROL_POWEROFF) {
                apm_cmd->command = ESM_APM_POWER_CYCLE;
                apm_cmd->reserved = 0;
                *((s16 *)&apm_cmd->parameters.shortreq.parm[0]) = (s16) 0;
                host_control_smi();
        } else if (action & HC_ACTION_HOST_CONTROL_POWERCYCLE) {
                apm_cmd->command = ESM_APM_POWER_CYCLE;
                apm_cmd->reserved = 0;
                *((s16 *)&apm_cmd->parameters.shortreq.parm[0]) = (s16) 20;
                host_control_smi();
        }
}

/* WSMT */

static u8 checksum(u8 *buffer, u8 length)
{
        u8 sum = 0;
        u8 *end = buffer + length;

        while (buffer < end)
                sum += *buffer++;
        return sum;
}

static inline struct smm_eps_table *check_eps_table(u8 *addr)
{
        struct smm_eps_table *eps = (struct smm_eps_table *)addr;

        if (strncmp(eps->smm_comm_buff_anchor, SMM_EPS_SIG, 4) != 0)
                return NULL;

        if (checksum(addr, eps->length) != 0)
                return NULL;

        return eps;
}

static int dcdbas_check_wsmt(void)
{
        const struct dmi_device *dev = NULL;
        struct acpi_table_wsmt *wsmt = NULL;
        struct smm_eps_table *eps = NULL;
        u64 bios_buf_paddr;
        u64 remap_size;
        u8 *addr;

        acpi_get_table(ACPI_SIG_WSMT, 0, (struct acpi_table_header **)&wsmt);
        if (!wsmt)
                return 0;

        /* Check if WSMT ACPI table shows that protection is enabled */
        if (!(wsmt->protection_flags & ACPI_WSMT_FIXED_COMM_BUFFERS) ||
            !(wsmt->protection_flags & ACPI_WSMT_COMM_BUFFER_NESTED_PTR_PROTECTION))
                return 0;

        /*
         * BIOS could provide the address/size of the protected buffer
         * in an SMBIOS string or in an EPS structure in 0xFxxxx.
         */

        /* Check SMBIOS for buffer address */
        while ((dev = dmi_find_device(DMI_DEV_TYPE_OEM_STRING, NULL, dev)))
                if (sscanf(dev->name, "30[%16llx;%8llx]", &bios_buf_paddr,
                    &remap_size) == 2)
                        goto remap;

        /* Scan for EPS (entry point structure) */
        for (addr = (u8 *)__va(0xf0000);
             addr < (u8 *)__va(0x100000 - sizeof(struct smm_eps_table));
             addr += 16) {
                eps = check_eps_table(addr);
                if (eps)
                        break;
        }

        if (!eps) {
                dev_dbg(&dcdbas_pdev->dev, "found WSMT, but no firmware buffer found\n");
                return -ENODEV;
        }
        bios_buf_paddr = eps->smm_comm_buff_addr;
        remap_size = eps->num_of_4k_pages * PAGE_SIZE;

remap:
        /*
         * Get physical address of buffer and map to virtual address.
         * Table gives size in 4K pages, regardless of actual system page size.
         */
        if (upper_32_bits(bios_buf_paddr + 8)) {
                dev_warn(&dcdbas_pdev->dev, "found WSMT, but buffer address is above 4GB\n");
                return -EINVAL;
        }
        /*
         * Limit remap size to MAX_SMI_DATA_BUF_SIZE + 8 (since the first 8
         * bytes are used for a semaphore, not the data buffer itself).
         */
        if (remap_size > MAX_SMI_DATA_BUF_SIZE + 8)
                remap_size = MAX_SMI_DATA_BUF_SIZE + 8;

        bios_buffer = memremap(bios_buf_paddr, remap_size, MEMREMAP_WB);
        if (!bios_buffer) {
                dev_warn(&dcdbas_pdev->dev, "found WSMT, but failed to map buffer\n");
                return -ENOMEM;
        }

        /* First 8 bytes is for a semaphore, not part of the smi_buf.virt */
        smi_buf.dma = bios_buf_paddr + 8;
        smi_buf.virt = bios_buffer + 8;
        smi_buf.size = remap_size - 8;
        max_smi_data_buf_size = smi_buf.size;
        wsmt_enabled = true;
        dev_info(&dcdbas_pdev->dev,
                 "WSMT found, using firmware-provided SMI buffer.\n");
        return 1;
}

/**
 * dcdbas_reboot_notify: handle reboot notification for host control
 */
static int dcdbas_reboot_notify(struct notifier_block *nb, unsigned long code,
                                void *unused)
{
        switch (code) {
        case SYS_DOWN:
        case SYS_HALT:
        case SYS_POWER_OFF:
                if (host_control_on_shutdown) {
                        /* firmware is going to perform host control action */
                        printk(KERN_WARNING "Please wait for shutdown "
                               "action to complete...\n");
                        dcdbas_host_control();
                }
                break;
        }

        return NOTIFY_DONE;
}

static struct notifier_block dcdbas_reboot_nb = {
        .notifier_call = dcdbas_reboot_notify,
        .next = NULL,
        .priority = INT_MIN
};

static const BIN_ATTR_ADMIN_RW(smi_data, 0);

static const struct bin_attribute *const dcdbas_bin_attrs[] = {
        &bin_attr_smi_data,
        NULL
};

static DCDBAS_DEV_ATTR_RW(smi_data_buf_size);
static DCDBAS_DEV_ATTR_RO(smi_data_buf_phys_addr);
static DCDBAS_DEV_ATTR_WO(smi_request);
static DCDBAS_DEV_ATTR_RW(host_control_action);
static DCDBAS_DEV_ATTR_RW(host_control_smi_type);
static DCDBAS_DEV_ATTR_RW(host_control_on_shutdown);

static struct attribute *dcdbas_dev_attrs[] = {
        &dev_attr_smi_data_buf_size.attr,
        &dev_attr_smi_data_buf_phys_addr.attr,
        &dev_attr_smi_request.attr,
        &dev_attr_host_control_action.attr,
        &dev_attr_host_control_smi_type.attr,
        &dev_attr_host_control_on_shutdown.attr,
        NULL
};

static const struct attribute_group dcdbas_attr_group = {
        .attrs = dcdbas_dev_attrs,
        .bin_attrs = dcdbas_bin_attrs,
};

static int dcdbas_probe(struct platform_device *dev)
{
        int error;

        host_control_action = HC_ACTION_NONE;
        host_control_smi_type = HC_SMITYPE_NONE;

        dcdbas_pdev = dev;

        /* Check if ACPI WSMT table specifies protected SMI buffer address */
        error = dcdbas_check_wsmt();
        if (error < 0)
                return error;

        /*
         * BIOS SMI calls require buffer addresses be in 32-bit address space.
         * This is done by setting the DMA mask below.
         */
        error = dma_set_coherent_mask(&dcdbas_pdev->dev, DMA_BIT_MASK(32));
        if (error)
                return error;

        error = sysfs_create_group(&dev->dev.kobj, &dcdbas_attr_group);
        if (error)
                return error;

        register_reboot_notifier(&dcdbas_reboot_nb);

        dev_info(&dev->dev, "%s (version %s)\n",
                 DRIVER_DESCRIPTION, DRIVER_VERSION);

        return 0;
}

static void dcdbas_remove(struct platform_device *dev)
{
        unregister_reboot_notifier(&dcdbas_reboot_nb);
        sysfs_remove_group(&dev->dev.kobj, &dcdbas_attr_group);
}

static struct platform_driver dcdbas_driver = {
        .driver         = {
                .name   = DRIVER_NAME,
        },
        .probe          = dcdbas_probe,
        .remove         = dcdbas_remove,
};

static const struct platform_device_info dcdbas_dev_info __initconst = {
        .name           = DRIVER_NAME,
        .id             = PLATFORM_DEVID_NONE,
        .dma_mask       = DMA_BIT_MASK(32),
};

static struct platform_device *dcdbas_pdev_reg;

/**
 * dcdbas_init: initialize driver
 */
static int __init dcdbas_init(void)
{
        int error;

        error = platform_driver_register(&dcdbas_driver);
        if (error)
                return error;

        dcdbas_pdev_reg = platform_device_register_full(&dcdbas_dev_info);
        if (IS_ERR(dcdbas_pdev_reg)) {
                error = PTR_ERR(dcdbas_pdev_reg);
                goto err_unregister_driver;
        }

        return 0;

 err_unregister_driver:
        platform_driver_unregister(&dcdbas_driver);
        return error;
}

/**
 * dcdbas_exit: perform driver cleanup
 */
static void __exit dcdbas_exit(void)
{
        /*
         * make sure functions that use dcdbas_pdev are called
         * before platform_device_unregister
         */
        unregister_reboot_notifier(&dcdbas_reboot_nb);

        /*
         * We have to free the buffer here instead of dcdbas_remove
         * because only in module exit function we can be sure that
         * all sysfs attributes belonging to this module have been
         * released.
         */
        if (dcdbas_pdev)
                smi_data_buf_free();
        if (bios_buffer)
                memunmap(bios_buffer);
        platform_device_unregister(dcdbas_pdev_reg);
        platform_driver_unregister(&dcdbas_driver);
}

subsys_initcall_sync(dcdbas_init);
module_exit(dcdbas_exit);

MODULE_DESCRIPTION(DRIVER_DESCRIPTION " (version " DRIVER_VERSION ")");
MODULE_VERSION(DRIVER_VERSION);
MODULE_AUTHOR("Dell Inc.");
MODULE_LICENSE("GPL");
/* Any System or BIOS claiming to be by Dell */
MODULE_ALIAS("dmi:*:[bs]vnD[Ee][Ll][Ll]*:*");