// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Marvell 88E6xxx System Management Interface (SMI) support
 *
 * Copyright (c) 2008 Marvell Semiconductor
 *
 * Copyright (c) 2019 Vivien Didelot <vivien.didelot@gmail.com>
 */

#include "chip.h"
#include "smi.h"

/* The switch ADDR[4:1] configuration pins define the chip SMI device address
 * (ADDR[0] is always zero, thus only even SMI addresses can be strapped).
 *
 * When ADDR is all zero, the chip uses Single-chip Addressing Mode, assuming it
 * is the only device connected to the SMI master. In this mode it responds to
 * all 32 possible SMI addresses, and thus maps directly the internal devices.
 *
 * When ADDR is non-zero, the chip uses Multi-chip Addressing Mode, allowing
 * multiple devices to share the SMI interface. In this mode it responds to only
 * 2 registers, used to indirectly access the internal SMI devices.
 *
 * Some chips use a different scheme: Only the ADDR4 pin is used for
 * configuration, and the device responds to 16 of the 32 SMI
 * addresses, allowing two to coexist on the same SMI interface.
 */

static int mv88e6xxx_smi_direct_read(struct mv88e6xxx_chip *chip,
                                     int dev, int reg, u16 *data)
{
        int ret;

        ret = mdiobus_read_nested(chip->bus, dev, reg);
        if (ret < 0)
                return ret;

        *data = ret & 0xffff;

        return 0;
}

static int mv88e6xxx_smi_direct_write(struct mv88e6xxx_chip *chip,
                                      int dev, int reg, u16 data)
{
        int ret;

        ret = mdiobus_write_nested(chip->bus, dev, reg, data);
        if (ret < 0)
                return ret;

        return 0;
}

static int mv88e6xxx_smi_direct_wait(struct mv88e6xxx_chip *chip,
                                     int dev, int reg, int bit, int val)
{
        const unsigned long timeout = jiffies + msecs_to_jiffies(50);
        u16 data;
        int err;
        int i;

        /* Even if the initial poll takes longer than 50ms, always do
         * at least one more attempt.
         */
        for (i = 0; time_before(jiffies, timeout) || (i < 2); i++) {
                err = mv88e6xxx_smi_direct_read(chip, dev, reg, &data);
                if (err)
                        return err;

                if (!!(data & BIT(bit)) == !!val)
                        return 0;

                if (i < 2)
                        cpu_relax();
                else
                        usleep_range(1000, 2000);
        }

        return -ETIMEDOUT;
}

static const struct mv88e6xxx_bus_ops mv88e6xxx_smi_direct_ops = {
        .read = mv88e6xxx_smi_direct_read,
        .write = mv88e6xxx_smi_direct_write,
};

static int mv88e6xxx_smi_dual_direct_read(struct mv88e6xxx_chip *chip,
                                          int dev, int reg, u16 *data)
{
        return mv88e6xxx_smi_direct_read(chip, chip->sw_addr + dev, reg, data);
}

static int mv88e6xxx_smi_dual_direct_write(struct mv88e6xxx_chip *chip,
                                           int dev, int reg, u16 data)
{
        return mv88e6xxx_smi_direct_write(chip, chip->sw_addr + dev, reg, data);
}

static const struct mv88e6xxx_bus_ops mv88e6xxx_smi_dual_direct_ops = {
        .read = mv88e6xxx_smi_dual_direct_read,
        .write = mv88e6xxx_smi_dual_direct_write,
};

/* Offset 0x00: SMI Command Register
 * Offset 0x01: SMI Data Register
 */

static int mv88e6xxx_smi_indirect_read(struct mv88e6xxx_chip *chip,
                                       int dev, int reg, u16 *data)
{
        int err;

        err = mv88e6xxx_smi_direct_write(chip, chip->sw_addr,
                                         MV88E6XXX_SMI_CMD,
                                         MV88E6XXX_SMI_CMD_BUSY |
                                         MV88E6XXX_SMI_CMD_MODE_22 |
                                         MV88E6XXX_SMI_CMD_OP_22_READ |
                                         (dev << 5) | reg);
        if (err)
                return err;

        err = mv88e6xxx_smi_direct_wait(chip, chip->sw_addr,
                                        MV88E6XXX_SMI_CMD, 15, 0);
        if (err)
                return err;

        return mv88e6xxx_smi_direct_read(chip, chip->sw_addr,
                                         MV88E6XXX_SMI_DATA, data);
}

static int mv88e6xxx_smi_indirect_write(struct mv88e6xxx_chip *chip,
                                        int dev, int reg, u16 data)
{
        int err;

        err = mv88e6xxx_smi_direct_write(chip, chip->sw_addr,
                                         MV88E6XXX_SMI_DATA, data);
        if (err)
                return err;

        err = mv88e6xxx_smi_direct_write(chip, chip->sw_addr,
                                         MV88E6XXX_SMI_CMD,
                                         MV88E6XXX_SMI_CMD_BUSY |
                                         MV88E6XXX_SMI_CMD_MODE_22 |
                                         MV88E6XXX_SMI_CMD_OP_22_WRITE |
                                         (dev << 5) | reg);
        if (err)
                return err;

        return mv88e6xxx_smi_direct_wait(chip, chip->sw_addr,
                                         MV88E6XXX_SMI_CMD, 15, 0);
}

static int mv88e6xxx_smi_indirect_init(struct mv88e6xxx_chip *chip)
{
        /* Ensure that the chip starts out in the ready state. As both
         * reads and writes always ensure this on return, they can
         * safely depend on the chip not being busy on entry.
         */
        return mv88e6xxx_smi_direct_wait(chip, chip->sw_addr,
                                         MV88E6XXX_SMI_CMD, 15, 0);
}

static const struct mv88e6xxx_bus_ops mv88e6xxx_smi_indirect_ops = {
        .read = mv88e6xxx_smi_indirect_read,
        .write = mv88e6xxx_smi_indirect_write,
        .init = mv88e6xxx_smi_indirect_init,
};

int mv88e6xxx_smi_init(struct mv88e6xxx_chip *chip,
                       struct mii_bus *bus, int sw_addr)
{
        if (chip->info->dual_chip)
                chip->smi_ops = &mv88e6xxx_smi_dual_direct_ops;
        else if (sw_addr == 0)
                chip->smi_ops = &mv88e6xxx_smi_direct_ops;
        else if (chip->info->multi_chip)
                chip->smi_ops = &mv88e6xxx_smi_indirect_ops;
        else
                return -EINVAL;

        chip->bus = bus;
        chip->sw_addr = sw_addr;

        if (chip->smi_ops->init)
                return chip->smi_ops->init(chip);

        return 0;
}