WIP FPC-III support

[linux/fpc-iii.git] / drivers / firmware / google / gsmi.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright 2010 Google Inc. All Rights Reserved.
 * Author: dlaurie@google.com (Duncan Laurie)
 *
 * Re-worked to expose sysfs APIs by mikew@google.com (Mike Waychison)
 *
 * EFI SMI interface for Google platforms
 */

#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/types.h>
#include <linux/device.h>
#include <linux/platform_device.h>
#include <linux/errno.h>
#include <linux/string.h>
#include <linux/spinlock.h>
#include <linux/dma-mapping.h>
#include <linux/fs.h>
#include <linux/slab.h>
#include <linux/ioctl.h>
#include <linux/acpi.h>
#include <linux/io.h>
#include <linux/uaccess.h>
#include <linux/dmi.h>
#include <linux/kdebug.h>
#include <linux/reboot.h>
#include <linux/efi.h>
#include <linux/module.h>
#include <linux/ucs2_string.h>
#include <linux/suspend.h>

#define GSMI_SHUTDOWN_CLEAN     0       /* Clean Shutdown */
/* TODO(mikew@google.com): Tie in HARDLOCKUP_DETECTOR with NMIWDT */
#define GSMI_SHUTDOWN_NMIWDT    1       /* NMI Watchdog */
#define GSMI_SHUTDOWN_PANIC     2       /* Panic */
#define GSMI_SHUTDOWN_OOPS      3       /* Oops */
#define GSMI_SHUTDOWN_DIE       4       /* Die -- No longer meaningful */
#define GSMI_SHUTDOWN_MCE       5       /* Machine Check */
#define GSMI_SHUTDOWN_SOFTWDT   6       /* Software Watchdog */
#define GSMI_SHUTDOWN_MBE       7       /* Uncorrected ECC */
#define GSMI_SHUTDOWN_TRIPLE    8       /* Triple Fault */

#define DRIVER_VERSION          "1.0"
#define GSMI_GUID_SIZE          16
#define GSMI_BUF_SIZE           1024
#define GSMI_BUF_ALIGN          sizeof(u64)
#define GSMI_CALLBACK           0xef

/* SMI return codes */
#define GSMI_SUCCESS            0x00
#define GSMI_UNSUPPORTED2       0x03
#define GSMI_LOG_FULL           0x0b
#define GSMI_VAR_NOT_FOUND      0x0e
#define GSMI_HANDSHAKE_SPIN     0x7d
#define GSMI_HANDSHAKE_CF       0x7e
#define GSMI_HANDSHAKE_NONE     0x7f
#define GSMI_INVALID_PARAMETER  0x82
#define GSMI_UNSUPPORTED        0x83
#define GSMI_BUFFER_TOO_SMALL   0x85
#define GSMI_NOT_READY          0x86
#define GSMI_DEVICE_ERROR       0x87
#define GSMI_NOT_FOUND          0x8e

#define QUIRKY_BOARD_HASH 0x78a30a50

/* Internally used commands passed to the firmware */
#define GSMI_CMD_GET_NVRAM_VAR          0x01
#define GSMI_CMD_GET_NEXT_VAR           0x02
#define GSMI_CMD_SET_NVRAM_VAR          0x03
#define GSMI_CMD_SET_EVENT_LOG          0x08
#define GSMI_CMD_CLEAR_EVENT_LOG        0x09
#define GSMI_CMD_LOG_S0IX_SUSPEND       0x0a
#define GSMI_CMD_LOG_S0IX_RESUME        0x0b
#define GSMI_CMD_CLEAR_CONFIG           0x20
#define GSMI_CMD_HANDSHAKE_TYPE         0xC1
#define GSMI_CMD_RESERVED               0xff

/* Magic entry type for kernel events */
#define GSMI_LOG_ENTRY_TYPE_KERNEL     0xDEAD

/* SMI buffers must be in 32bit physical address space */
struct gsmi_buf {
        u8 *start;                      /* start of buffer */
        size_t length;                  /* length of buffer */
        u32 address;                    /* physical address of buffer */
};

static struct gsmi_device {
        struct platform_device *pdev;   /* platform device */
        struct gsmi_buf *name_buf;      /* variable name buffer */
        struct gsmi_buf *data_buf;      /* generic data buffer */
        struct gsmi_buf *param_buf;     /* parameter buffer */
        spinlock_t lock;                /* serialize access to SMIs */
        u16 smi_cmd;                    /* SMI command port */
        int handshake_type;             /* firmware handler interlock type */
        struct kmem_cache *mem_pool;    /* kmem cache for gsmi_buf allocations */
} gsmi_dev;

/* Packed structures for communicating with the firmware */
struct gsmi_nvram_var_param {
        efi_guid_t      guid;
        u32             name_ptr;
        u32             attributes;
        u32             data_len;
        u32             data_ptr;
} __packed;

struct gsmi_get_next_var_param {
        u8      guid[GSMI_GUID_SIZE];
        u32     name_ptr;
        u32     name_len;
} __packed;

struct gsmi_set_eventlog_param {
        u32     data_ptr;
        u32     data_len;
        u32     type;
} __packed;

/* Event log formats */
struct gsmi_log_entry_type_1 {
        u16     type;
        u32     instance;
} __packed;

/*
 * Some platforms don't have explicit SMI handshake
 * and need to wait for SMI to complete.
 */
#define GSMI_DEFAULT_SPINCOUNT  0x10000
static unsigned int spincount = GSMI_DEFAULT_SPINCOUNT;
module_param(spincount, uint, 0600);
MODULE_PARM_DESC(spincount,
        "The number of loop iterations to use when using the spin handshake.");

/*
 * Platforms might not support S0ix logging in their GSMI handlers. In order to
 * avoid any side-effects of generating an SMI for S0ix logging, use the S0ix
 * related GSMI commands only for those platforms that explicitly enable this
 * option.
 */
static bool s0ix_logging_enable;
module_param(s0ix_logging_enable, bool, 0600);

static struct gsmi_buf *gsmi_buf_alloc(void)
{
        struct gsmi_buf *smibuf;

        smibuf = kzalloc(sizeof(*smibuf), GFP_KERNEL);
        if (!smibuf) {
                printk(KERN_ERR "gsmi: out of memory\n");
                return NULL;
        }

        /* allocate buffer in 32bit address space */
        smibuf->start = kmem_cache_alloc(gsmi_dev.mem_pool, GFP_KERNEL);
        if (!smibuf->start) {
                printk(KERN_ERR "gsmi: failed to allocate name buffer\n");
                kfree(smibuf);
                return NULL;
        }

        /* fill in the buffer handle */
        smibuf->length = GSMI_BUF_SIZE;
        smibuf->address = (u32)virt_to_phys(smibuf->start);

        return smibuf;
}

static void gsmi_buf_free(struct gsmi_buf *smibuf)
{
        if (smibuf) {
                if (smibuf->start)
                        kmem_cache_free(gsmi_dev.mem_pool, smibuf->start);
                kfree(smibuf);
        }
}

/*
 * Make a call to gsmi func(sub).  GSMI error codes are translated to
 * in-kernel errnos (0 on success, -ERRNO on error).
 */
static int gsmi_exec(u8 func, u8 sub)
{
        u16 cmd = (sub << 8) | func;
        u16 result = 0;
        int rc = 0;

        /*
         * AH  : Subfunction number
         * AL  : Function number
         * EBX : Parameter block address
         * DX  : SMI command port
         *
         * Three protocols here. See also the comment in gsmi_init().
         */
        if (gsmi_dev.handshake_type == GSMI_HANDSHAKE_CF) {
                /*
                 * If handshake_type == HANDSHAKE_CF then set CF on the
                 * way in and wait for the handler to clear it; this avoids
                 * corrupting register state on those chipsets which have
                 * a delay between writing the SMI trigger register and
                 * entering SMM.
                 */
                asm volatile (
                        "stc\n"
                        "outb %%al, %%dx\n"
                "1:      jc 1b\n"
                        : "=a" (result)
                        : "0" (cmd),
                          "d" (gsmi_dev.smi_cmd),
                          "b" (gsmi_dev.param_buf->address)
                        : "memory", "cc"
                );
        } else if (gsmi_dev.handshake_type == GSMI_HANDSHAKE_SPIN) {
                /*
                 * If handshake_type == HANDSHAKE_SPIN we spin a
                 * hundred-ish usecs to ensure the SMI has triggered.
                 */
                asm volatile (
                        "outb %%al, %%dx\n"
                "1:      loop 1b\n"
                        : "=a" (result)
                        : "0" (cmd),
                          "d" (gsmi_dev.smi_cmd),
                          "b" (gsmi_dev.param_buf->address),
                          "c" (spincount)
                        : "memory", "cc"
                );
        } else {
                /*
                 * If handshake_type == HANDSHAKE_NONE we do nothing;
                 * either we don't need to or it's legacy firmware that
                 * doesn't understand the CF protocol.
                 */
                asm volatile (
                        "outb %%al, %%dx\n\t"
                        : "=a" (result)
                        : "0" (cmd),
                          "d" (gsmi_dev.smi_cmd),
                          "b" (gsmi_dev.param_buf->address)
                        : "memory", "cc"
                );
        }

        /* check return code from SMI handler */
        switch (result) {
        case GSMI_SUCCESS:
                break;
        case GSMI_VAR_NOT_FOUND:
                /* not really an error, but let the caller know */
                rc = 1;
                break;
        case GSMI_INVALID_PARAMETER:
                printk(KERN_ERR "gsmi: exec 0x%04x: Invalid parameter\n", cmd);
                rc = -EINVAL;
                break;
        case GSMI_BUFFER_TOO_SMALL:
                printk(KERN_ERR "gsmi: exec 0x%04x: Buffer too small\n", cmd);
                rc = -ENOMEM;
                break;
        case GSMI_UNSUPPORTED:
        case GSMI_UNSUPPORTED2:
                if (sub != GSMI_CMD_HANDSHAKE_TYPE)
                        printk(KERN_ERR "gsmi: exec 0x%04x: Not supported\n",
                               cmd);
                rc = -ENOSYS;
                break;
        case GSMI_NOT_READY:
                printk(KERN_ERR "gsmi: exec 0x%04x: Not ready\n", cmd);
                rc = -EBUSY;
                break;
        case GSMI_DEVICE_ERROR:
                printk(KERN_ERR "gsmi: exec 0x%04x: Device error\n", cmd);
                rc = -EFAULT;
                break;
        case GSMI_NOT_FOUND:
                printk(KERN_ERR "gsmi: exec 0x%04x: Data not found\n", cmd);
                rc = -ENOENT;
                break;
        case GSMI_LOG_FULL:
                printk(KERN_ERR "gsmi: exec 0x%04x: Log full\n", cmd);
                rc = -ENOSPC;
                break;
        case GSMI_HANDSHAKE_CF:
        case GSMI_HANDSHAKE_SPIN:
        case GSMI_HANDSHAKE_NONE:
                rc = result;
                break;
        default:
                printk(KERN_ERR "gsmi: exec 0x%04x: Unknown error 0x%04x\n",
                       cmd, result);
                rc = -ENXIO;
        }

        return rc;
}

#ifdef CONFIG_EFI

static struct efivars efivars;

static efi_status_t gsmi_get_variable(efi_char16_t *name,
                                      efi_guid_t *vendor, u32 *attr,
                                      unsigned long *data_size,
                                      void *data)
{
        struct gsmi_nvram_var_param param = {
                .name_ptr = gsmi_dev.name_buf->address,
                .data_ptr = gsmi_dev.data_buf->address,
                .data_len = (u32)*data_size,
        };
        efi_status_t ret = EFI_SUCCESS;
        unsigned long flags;
        size_t name_len = ucs2_strnlen(name, GSMI_BUF_SIZE / 2);
        int rc;

        if (name_len >= GSMI_BUF_SIZE / 2)
                return EFI_BAD_BUFFER_SIZE;

        spin_lock_irqsave(&gsmi_dev.lock, flags);

        /* Vendor guid */
        memcpy(&param.guid, vendor, sizeof(param.guid));

        /* variable name, already in UTF-16 */
        memset(gsmi_dev.name_buf->start, 0, gsmi_dev.name_buf->length);
        memcpy(gsmi_dev.name_buf->start, name, name_len * 2);

        /* data pointer */
        memset(gsmi_dev.data_buf->start, 0, gsmi_dev.data_buf->length);

        /* parameter buffer */
        memset(gsmi_dev.param_buf->start, 0, gsmi_dev.param_buf->length);
        memcpy(gsmi_dev.param_buf->start, &param, sizeof(param));

        rc = gsmi_exec(GSMI_CALLBACK, GSMI_CMD_GET_NVRAM_VAR);
        if (rc < 0) {
                printk(KERN_ERR "gsmi: Get Variable failed\n");
                ret = EFI_LOAD_ERROR;
        } else if (rc == 1) {
                /* variable was not found */
                ret = EFI_NOT_FOUND;
        } else {
                /* Get the arguments back */
                memcpy(&param, gsmi_dev.param_buf->start, sizeof(param));

                /* The size reported is the min of all of our buffers */
                *data_size = min_t(unsigned long, *data_size,
                                                gsmi_dev.data_buf->length);
                *data_size = min_t(unsigned long, *data_size, param.data_len);

                /* Copy data back to return buffer. */
                memcpy(data, gsmi_dev.data_buf->start, *data_size);

                /* All variables are have the following attributes */
                *attr = EFI_VARIABLE_NON_VOLATILE |
                        EFI_VARIABLE_BOOTSERVICE_ACCESS |
                        EFI_VARIABLE_RUNTIME_ACCESS;
        }

        spin_unlock_irqrestore(&gsmi_dev.lock, flags);

        return ret;
}

static efi_status_t gsmi_get_next_variable(unsigned long *name_size,
                                           efi_char16_t *name,
                                           efi_guid_t *vendor)
{
        struct gsmi_get_next_var_param param = {
                .name_ptr = gsmi_dev.name_buf->address,
                .name_len = gsmi_dev.name_buf->length,
        };
        efi_status_t ret = EFI_SUCCESS;
        int rc;
        unsigned long flags;

        /* For the moment, only support buffers that exactly match in size */
        if (*name_size != GSMI_BUF_SIZE)
                return EFI_BAD_BUFFER_SIZE;

        /* Let's make sure the thing is at least null-terminated */
        if (ucs2_strnlen(name, GSMI_BUF_SIZE / 2) == GSMI_BUF_SIZE / 2)
                return EFI_INVALID_PARAMETER;

        spin_lock_irqsave(&gsmi_dev.lock, flags);

        /* guid */
        memcpy(&param.guid, vendor, sizeof(param.guid));

        /* variable name, already in UTF-16 */
        memcpy(gsmi_dev.name_buf->start, name, *name_size);

        /* parameter buffer */
        memset(gsmi_dev.param_buf->start, 0, gsmi_dev.param_buf->length);
        memcpy(gsmi_dev.param_buf->start, &param, sizeof(param));

        rc = gsmi_exec(GSMI_CALLBACK, GSMI_CMD_GET_NEXT_VAR);
        if (rc < 0) {
                printk(KERN_ERR "gsmi: Get Next Variable Name failed\n");
                ret = EFI_LOAD_ERROR;
        } else if (rc == 1) {
                /* variable not found -- end of list */
                ret = EFI_NOT_FOUND;
        } else {
                /* copy variable data back to return buffer */
                memcpy(&param, gsmi_dev.param_buf->start, sizeof(param));

                /* Copy the name back */
                memcpy(name, gsmi_dev.name_buf->start, GSMI_BUF_SIZE);
                *name_size = ucs2_strnlen(name, GSMI_BUF_SIZE / 2) * 2;

                /* copy guid to return buffer */
                memcpy(vendor, &param.guid, sizeof(param.guid));
                ret = EFI_SUCCESS;
        }

        spin_unlock_irqrestore(&gsmi_dev.lock, flags);

        return ret;
}

static efi_status_t gsmi_set_variable(efi_char16_t *name,
                                      efi_guid_t *vendor,
                                      u32 attr,
                                      unsigned long data_size,
                                      void *data)
{
        struct gsmi_nvram_var_param param = {
                .name_ptr = gsmi_dev.name_buf->address,
                .data_ptr = gsmi_dev.data_buf->address,
                .data_len = (u32)data_size,
                .attributes = EFI_VARIABLE_NON_VOLATILE |
                              EFI_VARIABLE_BOOTSERVICE_ACCESS |
                              EFI_VARIABLE_RUNTIME_ACCESS,
        };
        size_t name_len = ucs2_strnlen(name, GSMI_BUF_SIZE / 2);
        efi_status_t ret = EFI_SUCCESS;
        int rc;
        unsigned long flags;

        if (name_len >= GSMI_BUF_SIZE / 2)
                return EFI_BAD_BUFFER_SIZE;

        spin_lock_irqsave(&gsmi_dev.lock, flags);

        /* guid */
        memcpy(&param.guid, vendor, sizeof(param.guid));

        /* variable name, already in UTF-16 */
        memset(gsmi_dev.name_buf->start, 0, gsmi_dev.name_buf->length);
        memcpy(gsmi_dev.name_buf->start, name, name_len * 2);

        /* data pointer */
        memset(gsmi_dev.data_buf->start, 0, gsmi_dev.data_buf->length);
        memcpy(gsmi_dev.data_buf->start, data, data_size);

        /* parameter buffer */
        memset(gsmi_dev.param_buf->start, 0, gsmi_dev.param_buf->length);
        memcpy(gsmi_dev.param_buf->start, &param, sizeof(param));

        rc = gsmi_exec(GSMI_CALLBACK, GSMI_CMD_SET_NVRAM_VAR);
        if (rc < 0) {
                printk(KERN_ERR "gsmi: Set Variable failed\n");
                ret = EFI_INVALID_PARAMETER;
        }

        spin_unlock_irqrestore(&gsmi_dev.lock, flags);

        return ret;
}

static const struct efivar_operations efivar_ops = {
        .get_variable = gsmi_get_variable,
        .set_variable = gsmi_set_variable,
        .get_next_variable = gsmi_get_next_variable,
};

#endif /* CONFIG_EFI */

static ssize_t eventlog_write(struct file *filp, struct kobject *kobj,
                               struct bin_attribute *bin_attr,
                               char *buf, loff_t pos, size_t count)
{
        struct gsmi_set_eventlog_param param = {
                .data_ptr = gsmi_dev.data_buf->address,
        };
        int rc = 0;
        unsigned long flags;

        /* Pull the type out */
        if (count < sizeof(u32))
                return -EINVAL;
        param.type = *(u32 *)buf;
        buf += sizeof(u32);

        /* The remaining buffer is the data payload */
        if ((count - sizeof(u32)) > gsmi_dev.data_buf->length)
                return -EINVAL;
        param.data_len = count - sizeof(u32);

        spin_lock_irqsave(&gsmi_dev.lock, flags);

        /* data pointer */
        memset(gsmi_dev.data_buf->start, 0, gsmi_dev.data_buf->length);
        memcpy(gsmi_dev.data_buf->start, buf, param.data_len);

        /* parameter buffer */
        memset(gsmi_dev.param_buf->start, 0, gsmi_dev.param_buf->length);
        memcpy(gsmi_dev.param_buf->start, &param, sizeof(param));

        rc = gsmi_exec(GSMI_CALLBACK, GSMI_CMD_SET_EVENT_LOG);
        if (rc < 0)
                printk(KERN_ERR "gsmi: Set Event Log failed\n");

        spin_unlock_irqrestore(&gsmi_dev.lock, flags);

        return (rc == 0) ? count : rc;

}

static struct bin_attribute eventlog_bin_attr = {
        .attr = {.name = "append_to_eventlog", .mode = 0200},
        .write = eventlog_write,
};

static ssize_t gsmi_clear_eventlog_store(struct kobject *kobj,
                                         struct kobj_attribute *attr,
                                         const char *buf, size_t count)
{
        int rc;
        unsigned long flags;
        unsigned long val;
        struct {
                u32 percentage;
                u32 data_type;
        } param;

        rc = kstrtoul(buf, 0, &val);
        if (rc)
                return rc;

        /*
         * Value entered is a percentage, 0 through 100, anything else
         * is invalid.
         */
        if (val > 100)
                return -EINVAL;

        /* data_type here selects the smbios event log. */
        param.percentage = val;
        param.data_type = 0;

        spin_lock_irqsave(&gsmi_dev.lock, flags);

        /* parameter buffer */
        memset(gsmi_dev.param_buf->start, 0, gsmi_dev.param_buf->length);
        memcpy(gsmi_dev.param_buf->start, &param, sizeof(param));

        rc = gsmi_exec(GSMI_CALLBACK, GSMI_CMD_CLEAR_EVENT_LOG);

        spin_unlock_irqrestore(&gsmi_dev.lock, flags);

        if (rc)
                return rc;
        return count;
}

static struct kobj_attribute gsmi_clear_eventlog_attr = {
        .attr = {.name = "clear_eventlog", .mode = 0200},
        .store = gsmi_clear_eventlog_store,
};

static ssize_t gsmi_clear_config_store(struct kobject *kobj,
                                       struct kobj_attribute *attr,
                                       const char *buf, size_t count)
{
        int rc;
        unsigned long flags;

        spin_lock_irqsave(&gsmi_dev.lock, flags);

        /* clear parameter buffer */
        memset(gsmi_dev.param_buf->start, 0, gsmi_dev.param_buf->length);

        rc = gsmi_exec(GSMI_CALLBACK, GSMI_CMD_CLEAR_CONFIG);

        spin_unlock_irqrestore(&gsmi_dev.lock, flags);

        if (rc)
                return rc;
        return count;
}

static struct kobj_attribute gsmi_clear_config_attr = {
        .attr = {.name = "clear_config", .mode = 0200},
        .store = gsmi_clear_config_store,
};

static const struct attribute *gsmi_attrs[] = {
        &gsmi_clear_config_attr.attr,
        &gsmi_clear_eventlog_attr.attr,
        NULL,
};

static int gsmi_shutdown_reason(int reason)
{
        struct gsmi_log_entry_type_1 entry = {
                .type     = GSMI_LOG_ENTRY_TYPE_KERNEL,
                .instance = reason,
        };
        struct gsmi_set_eventlog_param param = {
                .data_len = sizeof(entry),
                .type     = 1,
        };
        static int saved_reason;
        int rc = 0;
        unsigned long flags;

        /* avoid duplicate entries in the log */
        if (saved_reason & (1 << reason))
                return 0;

        spin_lock_irqsave(&gsmi_dev.lock, flags);

        saved_reason |= (1 << reason);

        /* data pointer */
        memset(gsmi_dev.data_buf->start, 0, gsmi_dev.data_buf->length);
        memcpy(gsmi_dev.data_buf->start, &entry, sizeof(entry));

        /* parameter buffer */
        param.data_ptr = gsmi_dev.data_buf->address;
        memset(gsmi_dev.param_buf->start, 0, gsmi_dev.param_buf->length);
        memcpy(gsmi_dev.param_buf->start, &param, sizeof(param));

        rc = gsmi_exec(GSMI_CALLBACK, GSMI_CMD_SET_EVENT_LOG);

        spin_unlock_irqrestore(&gsmi_dev.lock, flags);

        if (rc < 0)
                printk(KERN_ERR "gsmi: Log Shutdown Reason failed\n");
        else
                printk(KERN_EMERG "gsmi: Log Shutdown Reason 0x%02x\n",
                       reason);

        return rc;
}

static int gsmi_reboot_callback(struct notifier_block *nb,
                                unsigned long reason, void *arg)
{
        gsmi_shutdown_reason(GSMI_SHUTDOWN_CLEAN);
        return NOTIFY_DONE;
}

static struct notifier_block gsmi_reboot_notifier = {
        .notifier_call = gsmi_reboot_callback
};

static int gsmi_die_callback(struct notifier_block *nb,
                             unsigned long reason, void *arg)
{
        if (reason == DIE_OOPS)
                gsmi_shutdown_reason(GSMI_SHUTDOWN_OOPS);
        return NOTIFY_DONE;
}

static struct notifier_block gsmi_die_notifier = {
        .notifier_call = gsmi_die_callback
};

static int gsmi_panic_callback(struct notifier_block *nb,
                               unsigned long reason, void *arg)
{
        gsmi_shutdown_reason(GSMI_SHUTDOWN_PANIC);
        return NOTIFY_DONE;
}

static struct notifier_block gsmi_panic_notifier = {
        .notifier_call = gsmi_panic_callback,
};

/*
 * This hash function was blatantly copied from include/linux/hash.h.
 * It is used by this driver to obfuscate a board name that requires a
 * quirk within this driver.
 *
 * Please do not remove this copy of the function as any changes to the
 * global utility hash_64() function would break this driver's ability
 * to identify a board and provide the appropriate quirk -- mikew@google.com
 */
static u64 __init local_hash_64(u64 val, unsigned bits)
{
        u64 hash = val;

        /*  Sigh, gcc can't optimise this alone like it does for 32 bits. */
        u64 n = hash;
        n <<= 18;
        hash -= n;
        n <<= 33;
        hash -= n;
        n <<= 3;
        hash += n;
        n <<= 3;
        hash -= n;
        n <<= 4;
        hash += n;
        n <<= 2;
        hash += n;

        /* High bits are more random, so use them. */
        return hash >> (64 - bits);
}

static u32 __init hash_oem_table_id(char s[8])
{
        u64 input;
        memcpy(&input, s, 8);
        return local_hash_64(input, 32);
}

static const struct dmi_system_id gsmi_dmi_table[] __initconst = {
        {
                .ident = "Google Board",
                .matches = {
                        DMI_MATCH(DMI_BOARD_VENDOR, "Google, Inc."),
                },
        },
        {
                .ident = "Coreboot Firmware",
                .matches = {
                        DMI_MATCH(DMI_BIOS_VENDOR, "coreboot"),
                },
        },
        {}
};
MODULE_DEVICE_TABLE(dmi, gsmi_dmi_table);

static __init int gsmi_system_valid(void)
{
        u32 hash;
        u16 cmd, result;

        if (!dmi_check_system(gsmi_dmi_table))
                return -ENODEV;

        /*
         * Only newer firmware supports the gsmi interface.  All older
         * firmware that didn't support this interface used to plug the
         * table name in the first four bytes of the oem_table_id field.
         * Newer firmware doesn't do that though, so use that as the
         * discriminant factor.  We have to do this in order to
         * whitewash our board names out of the public driver.
         */
        if (!strncmp(acpi_gbl_FADT.header.oem_table_id, "FACP", 4)) {
                printk(KERN_INFO "gsmi: Board is too old\n");
                return -ENODEV;
        }

        /* Disable on board with 1.0 BIOS due to Google bug 2602657 */
        hash = hash_oem_table_id(acpi_gbl_FADT.header.oem_table_id);
        if (hash == QUIRKY_BOARD_HASH) {
                const char *bios_ver = dmi_get_system_info(DMI_BIOS_VERSION);
                if (strncmp(bios_ver, "1.0", 3) == 0) {
                        pr_info("gsmi: disabled on this board's BIOS %s\n",
                                bios_ver);
                        return -ENODEV;
                }
        }

        /* check for valid SMI command port in ACPI FADT */
        if (acpi_gbl_FADT.smi_command == 0) {
                pr_info("gsmi: missing smi_command\n");
                return -ENODEV;
        }

        /* Test the smihandler with a bogus command. If it leaves the
         * calling argument in %ax untouched, there is no handler for
         * GSMI commands.
         */
        cmd = GSMI_CALLBACK | GSMI_CMD_RESERVED << 8;
        asm volatile (
                "outb %%al, %%dx\n\t"
                : "=a" (result)
                : "0" (cmd),
                  "d" (acpi_gbl_FADT.smi_command)
                : "memory", "cc"
                );
        if (cmd == result) {
                pr_info("gsmi: no gsmi handler in firmware\n");
                return -ENODEV;
        }

        /* Found */
        return 0;
}

static struct kobject *gsmi_kobj;

static const struct platform_device_info gsmi_dev_info = {
        .name           = "gsmi",
        .id             = -1,
        /* SMI callbacks require 32bit addresses */
        .dma_mask       = DMA_BIT_MASK(32),
};

#ifdef CONFIG_PM
static void gsmi_log_s0ix_info(u8 cmd)
{
        unsigned long flags;

        /*
         * If platform has not enabled S0ix logging, then no action is
         * necessary.
         */
        if (!s0ix_logging_enable)
                return;

        spin_lock_irqsave(&gsmi_dev.lock, flags);

        memset(gsmi_dev.param_buf->start, 0, gsmi_dev.param_buf->length);

        gsmi_exec(GSMI_CALLBACK, cmd);

        spin_unlock_irqrestore(&gsmi_dev.lock, flags);
}

static int gsmi_log_s0ix_suspend(struct device *dev)
{
        /*
         * If system is not suspending via firmware using the standard ACPI Sx
         * types, then make a GSMI call to log the suspend info.
         */
        if (!pm_suspend_via_firmware())
                gsmi_log_s0ix_info(GSMI_CMD_LOG_S0IX_SUSPEND);

        /*
         * Always return success, since we do not want suspend
         * to fail just because of logging failure.
         */
        return 0;
}

static int gsmi_log_s0ix_resume(struct device *dev)
{
        /*
         * If system did not resume via firmware, then make a GSMI call to log
         * the resume info and wake source.
         */
        if (!pm_resume_via_firmware())
                gsmi_log_s0ix_info(GSMI_CMD_LOG_S0IX_RESUME);

        /*
         * Always return success, since we do not want resume
         * to fail just because of logging failure.
         */
        return 0;
}

static const struct dev_pm_ops gsmi_pm_ops = {
        .suspend_noirq = gsmi_log_s0ix_suspend,
        .resume_noirq = gsmi_log_s0ix_resume,
};

static int gsmi_platform_driver_probe(struct platform_device *dev)
{
        return 0;
}

static struct platform_driver gsmi_driver_info = {
        .driver = {
                .name = "gsmi",
                .pm = &gsmi_pm_ops,
        },
        .probe = gsmi_platform_driver_probe,
};
#endif

static __init int gsmi_init(void)
{
        unsigned long flags;
        int ret;

        ret = gsmi_system_valid();
        if (ret)
                return ret;

        gsmi_dev.smi_cmd = acpi_gbl_FADT.smi_command;

#ifdef CONFIG_PM
        ret = platform_driver_register(&gsmi_driver_info);
        if (unlikely(ret)) {
                printk(KERN_ERR "gsmi: unable to register platform driver\n");
                return ret;
        }
#endif

        /* register device */
        gsmi_dev.pdev = platform_device_register_full(&gsmi_dev_info);
        if (IS_ERR(gsmi_dev.pdev)) {
                printk(KERN_ERR "gsmi: unable to register platform device\n");
                return PTR_ERR(gsmi_dev.pdev);
        }

        /* SMI access needs to be serialized */
        spin_lock_init(&gsmi_dev.lock);

        ret = -ENOMEM;

        /*
         * SLAB cache is created using SLAB_CACHE_DMA32 to ensure that the
         * allocations for gsmi_buf come from the DMA32 memory zone. These
         * buffers have nothing to do with DMA. They are required for
         * communication with firmware executing in SMI mode which can only
         * access the bottom 4GiB of physical memory. Since DMA32 memory zone
         * guarantees allocation under the 4GiB boundary, this driver creates
         * a SLAB cache with SLAB_CACHE_DMA32 flag.
         */
        gsmi_dev.mem_pool = kmem_cache_create("gsmi", GSMI_BUF_SIZE,
                                              GSMI_BUF_ALIGN,
                                              SLAB_CACHE_DMA32, NULL);
        if (!gsmi_dev.mem_pool)
                goto out_err;

        /*
         * pre-allocate buffers because sometimes we are called when
         * this is not feasible: oops, panic, die, mce, etc
         */
        gsmi_dev.name_buf = gsmi_buf_alloc();
        if (!gsmi_dev.name_buf) {
                printk(KERN_ERR "gsmi: failed to allocate name buffer\n");
                goto out_err;
        }

        gsmi_dev.data_buf = gsmi_buf_alloc();
        if (!gsmi_dev.data_buf) {
                printk(KERN_ERR "gsmi: failed to allocate data buffer\n");
                goto out_err;
        }

        gsmi_dev.param_buf = gsmi_buf_alloc();
        if (!gsmi_dev.param_buf) {
                printk(KERN_ERR "gsmi: failed to allocate param buffer\n");
                goto out_err;
        }

        /*
         * Determine type of handshake used to serialize the SMI
         * entry. See also gsmi_exec().
         *
         * There's a "behavior" present on some chipsets where writing the
         * SMI trigger register in the southbridge doesn't result in an
         * immediate SMI. Rather, the processor can execute "a few" more
         * instructions before the SMI takes effect. To ensure synchronous
         * behavior, implement a handshake between the kernel driver and the
         * firmware handler to spin until released. This ioctl determines
         * the type of handshake.
         *
         * NONE: The firmware handler does not implement any
         * handshake. Either it doesn't need to, or it's legacy firmware
         * that doesn't know it needs to and never will.
         *
         * CF: The firmware handler will clear the CF in the saved
         * state before returning. The driver may set the CF and test for
         * it to clear before proceeding.
         *
         * SPIN: The firmware handler does not implement any handshake
         * but the driver should spin for a hundred or so microseconds
         * to ensure the SMI has triggered.
         *
         * Finally, the handler will return -ENOSYS if
         * GSMI_CMD_HANDSHAKE_TYPE is unimplemented, which implies
         * HANDSHAKE_NONE.
         */
        spin_lock_irqsave(&gsmi_dev.lock, flags);
        gsmi_dev.handshake_type = GSMI_HANDSHAKE_SPIN;
        gsmi_dev.handshake_type =
            gsmi_exec(GSMI_CALLBACK, GSMI_CMD_HANDSHAKE_TYPE);
        if (gsmi_dev.handshake_type == -ENOSYS)
                gsmi_dev.handshake_type = GSMI_HANDSHAKE_NONE;
        spin_unlock_irqrestore(&gsmi_dev.lock, flags);

        /* Remove and clean up gsmi if the handshake could not complete. */
        if (gsmi_dev.handshake_type == -ENXIO) {
                printk(KERN_INFO "gsmi version " DRIVER_VERSION
                       " failed to load\n");
                ret = -ENODEV;
                goto out_err;
        }

        /* Register in the firmware directory */
        ret = -ENOMEM;
        gsmi_kobj = kobject_create_and_add("gsmi", firmware_kobj);
        if (!gsmi_kobj) {
                printk(KERN_INFO "gsmi: Failed to create firmware kobj\n");
                goto out_err;
        }

        /* Setup eventlog access */
        ret = sysfs_create_bin_file(gsmi_kobj, &eventlog_bin_attr);
        if (ret) {
                printk(KERN_INFO "gsmi: Failed to setup eventlog");
                goto out_err;
        }

        /* Other attributes */
        ret = sysfs_create_files(gsmi_kobj, gsmi_attrs);
        if (ret) {
                printk(KERN_INFO "gsmi: Failed to add attrs");
                goto out_remove_bin_file;
        }

#ifdef CONFIG_EFI
        ret = efivars_register(&efivars, &efivar_ops, gsmi_kobj);
        if (ret) {
                printk(KERN_INFO "gsmi: Failed to register efivars\n");
                sysfs_remove_files(gsmi_kobj, gsmi_attrs);
                goto out_remove_bin_file;
        }
#endif

        register_reboot_notifier(&gsmi_reboot_notifier);
        register_die_notifier(&gsmi_die_notifier);
        atomic_notifier_chain_register(&panic_notifier_list,
                                       &gsmi_panic_notifier);

        printk(KERN_INFO "gsmi version " DRIVER_VERSION " loaded\n");

        return 0;

out_remove_bin_file:
        sysfs_remove_bin_file(gsmi_kobj, &eventlog_bin_attr);
out_err:
        kobject_put(gsmi_kobj);
        gsmi_buf_free(gsmi_dev.param_buf);
        gsmi_buf_free(gsmi_dev.data_buf);
        gsmi_buf_free(gsmi_dev.name_buf);
        kmem_cache_destroy(gsmi_dev.mem_pool);
        platform_device_unregister(gsmi_dev.pdev);
        pr_info("gsmi: failed to load: %d\n", ret);
#ifdef CONFIG_PM
        platform_driver_unregister(&gsmi_driver_info);
#endif
        return ret;
}

static void __exit gsmi_exit(void)
{
        unregister_reboot_notifier(&gsmi_reboot_notifier);
        unregister_die_notifier(&gsmi_die_notifier);
        atomic_notifier_chain_unregister(&panic_notifier_list,
                                         &gsmi_panic_notifier);
#ifdef CONFIG_EFI
        efivars_unregister(&efivars);
#endif

        sysfs_remove_files(gsmi_kobj, gsmi_attrs);
        sysfs_remove_bin_file(gsmi_kobj, &eventlog_bin_attr);
        kobject_put(gsmi_kobj);
        gsmi_buf_free(gsmi_dev.param_buf);
        gsmi_buf_free(gsmi_dev.data_buf);
        gsmi_buf_free(gsmi_dev.name_buf);
        kmem_cache_destroy(gsmi_dev.mem_pool);
        platform_device_unregister(gsmi_dev.pdev);
#ifdef CONFIG_PM
        platform_driver_unregister(&gsmi_driver_info);
#endif
}

module_init(gsmi_init);
module_exit(gsmi_exit);

MODULE_AUTHOR("Google, Inc.");
MODULE_LICENSE("GPL");