// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (C) 2020 BAIKAL ELECTRONICS, JSC
 *
 * Authors:
 *   Serge Semin <Sergey.Semin@baikalelectronics.ru>
 *
 * Baikal-T1 Physically Mapped Internal ROM driver
 */
#include <linux/bits.h>
#include <linux/device.h>
#include <linux/kernel.h>
#include <linux/mtd/map.h>
#include <linux/mtd/xip.h>
#include <linux/mux/consumer.h>
#include <linux/of.h>
#include <linux/platform_device.h>
#include <linux/string.h>
#include <linux/types.h>

#include "physmap-bt1-rom.h"

/*
 * Baikal-T1 SoC ROMs are only accessible by the dword-aligned instructions.
 * We have to take this into account when implementing the data read-methods.
 * Note there is no need in bothering with endianness, since both Baikal-T1
 * CPU and MMIO are LE.
 */
static map_word __xipram bt1_rom_map_read(struct map_info *map,
                                          unsigned long ofs)
{
        void __iomem *src = map->virt + ofs;
        unsigned int shift;
        map_word ret;
        u32 data;

        /* Read data within offset dword. */
        shift = (uintptr_t)src & 0x3;
        data = readl_relaxed(src - shift);
        if (!shift) {
                ret.x[0] = data;
                return ret;
        }
        ret.x[0] = data >> (shift * BITS_PER_BYTE);

        /* Read data from the next dword. */
        shift = 4 - shift;
        if (ofs + shift >= map->size)
                return ret;

        data = readl_relaxed(src + shift);
        ret.x[0] |= data << (shift * BITS_PER_BYTE);

        return ret;
}

static void __xipram bt1_rom_map_copy_from(struct map_info *map,
                                           void *to, unsigned long from,
                                           ssize_t len)
{
        void __iomem *src = map->virt + from;
        unsigned int shift, chunk;
        u32 data;

        if (len <= 0 || from >= map->size)
                return;

        /* Make sure we don't go over the map limit. */
        len = min_t(ssize_t, map->size - from, len);

        /*
         * Since requested data size can be pretty big we have to implement
         * the copy procedure as optimal as possible. That's why it's split
         * up into the next three stages: unaligned head, aligned body,
         * unaligned tail.
         */
        shift = (uintptr_t)src & 0x3;
        if (shift) {
                chunk = min_t(ssize_t, 4 - shift, len);
                data = readl_relaxed(src - shift);
                memcpy(to, (char *)&data + shift, chunk);
                src += chunk;
                to += chunk;
                len -= chunk;
        }

        while (len >= 4) {
                data = readl_relaxed(src);
                memcpy(to, &data, 4);
                src += 4;
                to += 4;
                len -= 4;
        }

        if (len) {
                data = readl_relaxed(src);
                memcpy(to, &data, len);
        }
}

int of_flash_probe_bt1_rom(struct platform_device *pdev,
                           struct device_node *np,
                           struct map_info *map)
{
        struct device *dev = &pdev->dev;

        /* It's supposed to be read-only MTD. */
        if (!of_device_is_compatible(np, "mtd-rom")) {
                dev_info(dev, "No mtd-rom compatible string\n");
                return 0;
        }

        /* Multiplatform guard. */
        if (!of_device_is_compatible(np, "baikal,bt1-int-rom"))
                return 0;

        /* Sanity check the device parameters retrieved from DTB. */
        if (map->bankwidth != 4)
                dev_warn(dev, "Bank width is supposed to be 32 bits wide\n");

        map->read = bt1_rom_map_read;
        map->copy_from = bt1_rom_map_copy_from;

        return 0;
}