// SPDX-License-Identifier: GPL-2.0
/*
 * Thunderbolt driver - capabilities lookup
 *
 * Copyright (c) 2014 Andreas Noever <andreas.noever@gmail.com>
 * Copyright (C) 2018, Intel Corporation
 */

#include <linux/slab.h>
#include <linux/errno.h>

#include "tb.h"

#define CAP_OFFSET_MAX          0xff
#define VSE_CAP_OFFSET_MAX      0xffff
#define TMU_ACCESS_EN           BIT(20)

static int tb_port_enable_tmu(struct tb_port *port, bool enable)
{
        struct tb_switch *sw = port->sw;
        u32 value, offset;
        int ret;

        /*
         * Legacy devices need to have TMU access enabled before port
         * space can be fully accessed.
         */
        if (tb_switch_is_light_ridge(sw))
                offset = 0x26;
        else if (tb_switch_is_eagle_ridge(sw))
                offset = 0x2a;
        else
                return 0;

        ret = tb_sw_read(sw, &value, TB_CFG_SWITCH, offset, 1);
        if (ret)
                return ret;

        if (enable)
                value |= TMU_ACCESS_EN;
        else
                value &= ~TMU_ACCESS_EN;

        return tb_sw_write(sw, &value, TB_CFG_SWITCH, offset, 1);
}

static void tb_port_dummy_read(struct tb_port *port)
{
        /*
         * When reading from next capability pointer location in port
         * config space the read data is not cleared on LR. To avoid
         * reading stale data on next read perform one dummy read after
         * port capabilities are walked.
         */
        if (tb_switch_is_light_ridge(port->sw)) {
                u32 dummy;

                tb_port_read(port, &dummy, TB_CFG_PORT, 0, 1);
        }
}

/**
 * tb_port_next_cap() - Return next capability in the linked list
 * @port: Port to find the capability for
 * @offset: Previous capability offset (%0 for start)
 *
 * Returns dword offset of the next capability in port config space
 * capability list and returns it. Passing %0 returns the first entry in
 * the capability list. If no next capability is found returns %0. In case
 * of failure returns negative errno.
 */
int tb_port_next_cap(struct tb_port *port, unsigned int offset)
{
        struct tb_cap_any header;
        int ret;

        if (!offset)
                return port->config.first_cap_offset;

        ret = tb_port_read(port, &header, TB_CFG_PORT, offset, 1);
        if (ret)
                return ret;

        return header.basic.next;
}

static int __tb_port_find_cap(struct tb_port *port, enum tb_port_cap cap)
{
        int offset = 0;

        do {
                struct tb_cap_any header;
                int ret;

                offset = tb_port_next_cap(port, offset);
                if (offset < 0)
                        return offset;

                ret = tb_port_read(port, &header, TB_CFG_PORT, offset, 1);
                if (ret)
                        return ret;

                if (header.basic.cap == cap)
                        return offset;
        } while (offset > 0);

        return -ENOENT;
}

/**
 * tb_port_find_cap() - Find port capability
 * @port: Port to find the capability for
 * @cap: Capability to look
 *
 * Returns offset to start of capability or %-ENOENT if no such
 * capability was found. Negative errno is returned if there was an
 * error.
 */
int tb_port_find_cap(struct tb_port *port, enum tb_port_cap cap)
{
        int ret;

        ret = tb_port_enable_tmu(port, true);
        if (ret)
                return ret;

        ret = __tb_port_find_cap(port, cap);

        tb_port_dummy_read(port);
        tb_port_enable_tmu(port, false);

        return ret;
}

/**
 * tb_switch_next_cap() - Return next capability in the linked list
 * @sw: Switch to find the capability for
 * @offset: Previous capability offset (%0 for start)
 *
 * Finds dword offset of the next capability in router config space
 * capability list and returns it. Passing %0 returns the first entry in
 * the capability list. If no next capability is found returns %0. In case
 * of failure returns negative errno.
 */
int tb_switch_next_cap(struct tb_switch *sw, unsigned int offset)
{
        struct tb_cap_any header;
        int ret;

        if (!offset)
                return sw->config.first_cap_offset;

        ret = tb_sw_read(sw, &header, TB_CFG_SWITCH, offset, 2);
        if (ret)
                return ret;

        switch (header.basic.cap) {
        case TB_SWITCH_CAP_TMU:
                ret = header.basic.next;
                break;

        case TB_SWITCH_CAP_VSE:
                if (!header.extended_short.length)
                        ret = header.extended_long.next;
                else
                        ret = header.extended_short.next;
                break;

        default:
                tb_sw_dbg(sw, "unknown capability %#x at %#x\n",
                          header.basic.cap, offset);
                ret = -EINVAL;
                break;
        }

        return ret >= VSE_CAP_OFFSET_MAX ? 0 : ret;
}

/**
 * tb_switch_find_cap() - Find switch capability
 * @sw: Switch to find the capability for
 * @cap: Capability to look
 *
 * Returns offset to start of capability or %-ENOENT if no such
 * capability was found. Negative errno is returned if there was an
 * error.
 */
int tb_switch_find_cap(struct tb_switch *sw, enum tb_switch_cap cap)
{
        int offset = 0;

        do {
                struct tb_cap_any header;
                int ret;

                offset = tb_switch_next_cap(sw, offset);
                if (offset < 0)
                        return offset;

                ret = tb_sw_read(sw, &header, TB_CFG_SWITCH, offset, 1);
                if (ret)
                        return ret;

                if (header.basic.cap == cap)
                        return offset;
        } while (offset);

        return -ENOENT;
}

/**
 * tb_switch_find_vse_cap() - Find switch vendor specific capability
 * @sw: Switch to find the capability for
 * @vsec: Vendor specific capability to look
 *
 * Functions enumerates vendor specific capabilities (VSEC) of a switch
 * and returns offset when capability matching @vsec is found. If no
 * such capability is found returns %-ENOENT. In case of error returns
 * negative errno.
 */
int tb_switch_find_vse_cap(struct tb_switch *sw, enum tb_switch_vse_cap vsec)
{
        int offset = 0;

        do {
                struct tb_cap_any header;
                int ret;

                offset = tb_switch_next_cap(sw, offset);
                if (offset < 0)
                        return offset;

                ret = tb_sw_read(sw, &header, TB_CFG_SWITCH, offset, 1);
                if (ret)
                        return ret;

                if (header.extended_short.cap == TB_SWITCH_CAP_VSE &&
                    header.extended_short.vsec_id == vsec)
                        return offset;
        } while (offset);

        return -ENOENT;
}