// SPDX-License-Identifier: GPL-2.0
// LPC variant I/O for Microchip EC
//
// Copyright (C) 2016 Google, Inc

#include <linux/delay.h>
#include <linux/io.h>
#include <linux/mutex.h>
#include <linux/types.h>

#include "cros_ec_lpc_mec.h"

#define ACPI_LOCK_DELAY_MS 500

/*
 * This mutex must be held while accessing the EMI unit. We can't rely on the
 * EC mutex because memmap data may be accessed without it being held.
 */
static DEFINE_MUTEX(io_mutex);
/*
 * An alternative mutex to be used when the ACPI AML code may also
 * access memmap data.  When set, this mutex is used in preference to
 * io_mutex.
 */
static acpi_handle aml_mutex;

static u16 mec_emi_base, mec_emi_end;

/**
 * cros_ec_lpc_mec_lock() - Acquire mutex for EMI
 *
 * @return: Negative error code, or zero for success
 */
static int cros_ec_lpc_mec_lock(void)
{
        bool success;

        if (!aml_mutex) {
                mutex_lock(&io_mutex);
                return 0;
        }

        success = ACPI_SUCCESS(acpi_acquire_mutex(aml_mutex,
                                                  NULL, ACPI_LOCK_DELAY_MS));
        if (!success)
                return -EBUSY;

        return 0;
}

/**
 * cros_ec_lpc_mec_unlock() - Release mutex for EMI
 *
 * @return: Negative error code, or zero for success
 */
static int cros_ec_lpc_mec_unlock(void)
{
        bool success;

        if (!aml_mutex) {
                mutex_unlock(&io_mutex);
                return 0;
        }

        success = ACPI_SUCCESS(acpi_release_mutex(aml_mutex, NULL));
        if (!success)
                return -EBUSY;

        return 0;
}

/**
 * cros_ec_lpc_mec_emi_write_address() - Initialize EMI at a given address.
 *
 * @addr: Starting read / write address
 * @access_type: Type of access, typically 32-bit auto-increment
 */
static void cros_ec_lpc_mec_emi_write_address(u16 addr,
                        enum cros_ec_lpc_mec_emi_access_mode access_type)
{
        outb((addr & 0xfc) | access_type, MEC_EMI_EC_ADDRESS_B0(mec_emi_base));
        outb((addr >> 8) & 0x7f, MEC_EMI_EC_ADDRESS_B1(mec_emi_base));
}

/**
 * cros_ec_lpc_mec_in_range() - Determine if addresses are in MEC EMI range.
 *
 * @offset: Address offset
 * @length: Number of bytes to check
 *
 * Return: 1 if in range, 0 if not, and -EINVAL on failure
 *         such as the mec range not being initialized
 */
int cros_ec_lpc_mec_in_range(unsigned int offset, unsigned int length)
{
        if (WARN_ON(mec_emi_base == 0 || mec_emi_end == 0))
                return -EINVAL;

        if (offset >= mec_emi_base && offset < mec_emi_end) {
                if (WARN_ON(offset + length - 1 >= mec_emi_end))
                        return -EINVAL;
                return 1;
        }

        if (WARN_ON(offset + length > mec_emi_base && offset < mec_emi_end))
                return -EINVAL;

        return 0;
}

/**
 * cros_ec_lpc_io_bytes_mec() - Read / write bytes to MEC EMI port.
 *
 * @io_type: MEC_IO_READ or MEC_IO_WRITE, depending on request
 * @offset:  Base read / write address
 * @length:  Number of bytes to read / write
 * @buf:     Destination / source buffer
 *
 * @return:  A negative error code on error, or 8-bit checksum of all
 *           bytes read / written
 */
int cros_ec_lpc_io_bytes_mec(enum cros_ec_lpc_mec_io_type io_type,
                             unsigned int offset, unsigned int length,
                             u8 *buf)
{
        int i = 0;
        int io_addr;
        u8 sum = 0;
        enum cros_ec_lpc_mec_emi_access_mode access, new_access;
        int ret;

        if (length == 0)
                return 0;

        /* Return checksum of 0 if window is not initialized */
        WARN_ON(mec_emi_base == 0 || mec_emi_end == 0);
        if (mec_emi_base == 0 || mec_emi_end == 0)
                return 0;

        /*
         * Long access cannot be used on misaligned data since reading B0 loads
         * the data register and writing B3 flushes.
         */
        if (offset & 0x3 || length < 4)
                access = ACCESS_TYPE_BYTE;
        else
                access = ACCESS_TYPE_LONG_AUTO_INCREMENT;

        ret = cros_ec_lpc_mec_lock();
        if (ret)
                return ret;

        /* Initialize I/O at desired address */
        cros_ec_lpc_mec_emi_write_address(offset, access);

        /* Skip bytes in case of misaligned offset */
        io_addr = MEC_EMI_EC_DATA_B0(mec_emi_base) + (offset & 0x3);
        while (i < length) {
                while (io_addr <= MEC_EMI_EC_DATA_B3(mec_emi_base)) {
                        if (io_type == MEC_IO_READ)
                                buf[i] = inb(io_addr++);
                        else
                                outb(buf[i], io_addr++);

                        sum += buf[i++];
                        offset++;

                        /* Extra bounds check in case of misaligned length */
                        if (i == length)
                                goto done;
                }

                /*
                 * Use long auto-increment access except for misaligned write,
                 * since writing B3 triggers the flush.
                 */
                if (length - i < 4 && io_type == MEC_IO_WRITE)
                        new_access = ACCESS_TYPE_BYTE;
                else
                        new_access = ACCESS_TYPE_LONG_AUTO_INCREMENT;

                if (new_access != access ||
                    access != ACCESS_TYPE_LONG_AUTO_INCREMENT) {
                        access = new_access;
                        cros_ec_lpc_mec_emi_write_address(offset, access);
                }

                /* Access [B0, B3] on each loop pass */
                io_addr = MEC_EMI_EC_DATA_B0(mec_emi_base);
        }

done:
        ret = cros_ec_lpc_mec_unlock();
        if (ret)
                return ret;

        return sum;
}
EXPORT_SYMBOL(cros_ec_lpc_io_bytes_mec);

void cros_ec_lpc_mec_init(unsigned int base, unsigned int end)
{
        mec_emi_base = base;
        mec_emi_end = end;
}
EXPORT_SYMBOL(cros_ec_lpc_mec_init);

int cros_ec_lpc_mec_acpi_mutex(struct acpi_device *adev, const char *pathname)
{
        int status;

        if (!adev)
                return -ENOENT;

        status = acpi_get_handle(adev->handle, pathname, &aml_mutex);
        if (ACPI_FAILURE(status))
                return -ENOENT;

        return 0;
}
EXPORT_SYMBOL(cros_ec_lpc_mec_acpi_mutex);