/*
 * Copyright (C) 2012 Google, Inc.
 *
 * This software is licensed under the terms of the GNU General Public
 * License version 2, as published by the Free Software Foundation, and
 * may be copied, distributed, and modified under those terms.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 */

#include <linux/device.h>
#include <linux/err.h>
#include <linux/errno.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/io.h>
#include <linux/list.h>
#include <linux/memblock.h>
#include <linux/rslib.h>
#include <linux/slab.h>
#include <linux/vmalloc.h>
#include <linux/pstore_ram.h>
#include <asm/page.h>

struct persistent_ram_buffer {
        uint32_t    sig;
        atomic_t    start;
        atomic_t    size;
        uint8_t     data[0];
};

#define PERSISTENT_RAM_SIG (0x43474244) /* DBGC */

static inline size_t buffer_size(struct persistent_ram_zone *prz)
{
        return atomic_read(&prz->buffer->size);
}

static inline size_t buffer_start(struct persistent_ram_zone *prz)
{
        return atomic_read(&prz->buffer->start);
}

/* increase and wrap the start pointer, returning the old value */
static inline size_t buffer_start_add(struct persistent_ram_zone *prz, size_t a)
{
        int old;
        int new;

        do {
                old = atomic_read(&prz->buffer->start);
                new = old + a;
                while (unlikely(new > prz->buffer_size))
                        new -= prz->buffer_size;
        } while (atomic_cmpxchg(&prz->buffer->start, old, new) != old);

        return old;
}

/* increase the size counter until it hits the max size */
static inline void buffer_size_add(struct persistent_ram_zone *prz, size_t a)
{
        size_t old;
        size_t new;

        if (atomic_read(&prz->buffer->size) == prz->buffer_size)
                return;

        do {
                old = atomic_read(&prz->buffer->size);
                new = old + a;
                if (new > prz->buffer_size)
                        new = prz->buffer_size;
        } while (atomic_cmpxchg(&prz->buffer->size, old, new) != old);
}

static void notrace persistent_ram_encode_rs8(struct persistent_ram_zone *prz,
        uint8_t *data, size_t len, uint8_t *ecc)
{
        int i;
        uint16_t par[prz->ecc_info.ecc_size];

        /* Initialize the parity buffer */
        memset(par, 0, sizeof(par));
        encode_rs8(prz->rs_decoder, data, len, par, 0);
        for (i = 0; i < prz->ecc_info.ecc_size; i++)
                ecc[i] = par[i];
}

static int persistent_ram_decode_rs8(struct persistent_ram_zone *prz,
        void *data, size_t len, uint8_t *ecc)
{
        int i;
        uint16_t par[prz->ecc_info.ecc_size];

        for (i = 0; i < prz->ecc_info.ecc_size; i++)
                par[i] = ecc[i];
        return decode_rs8(prz->rs_decoder, data, par, len,
                                NULL, 0, NULL, 0, NULL);
}

static void notrace persistent_ram_update_ecc(struct persistent_ram_zone *prz,
        unsigned int start, unsigned int count)
{
        struct persistent_ram_buffer *buffer = prz->buffer;
        uint8_t *buffer_end = buffer->data + prz->buffer_size;
        uint8_t *block;
        uint8_t *par;
        int ecc_block_size = prz->ecc_info.block_size;
        int ecc_size = prz->ecc_info.ecc_size;
        int size = ecc_block_size;

        if (!ecc_size)
                return;

        block = buffer->data + (start & ~(ecc_block_size - 1));
        par = prz->par_buffer + (start / ecc_block_size) * ecc_size;

        do {
                if (block + ecc_block_size > buffer_end)
                        size = buffer_end - block;
                persistent_ram_encode_rs8(prz, block, size, par);
                block += ecc_block_size;
                par += ecc_size;
        } while (block < buffer->data + start + count);
}

static void persistent_ram_update_header_ecc(struct persistent_ram_zone *prz)
{
        struct persistent_ram_buffer *buffer = prz->buffer;

        if (!prz->ecc_info.ecc_size)
                return;

        persistent_ram_encode_rs8(prz, (uint8_t *)buffer, sizeof(*buffer),
                                  prz->par_header);
}

static void persistent_ram_ecc_old(struct persistent_ram_zone *prz)
{
        struct persistent_ram_buffer *buffer = prz->buffer;
        uint8_t *block;
        uint8_t *par;

        if (!prz->ecc_info.ecc_size)
                return;

        block = buffer->data;
        par = prz->par_buffer;
        while (block < buffer->data + buffer_size(prz)) {
                int numerr;
                int size = prz->ecc_info.block_size;
                if (block + size > buffer->data + prz->buffer_size)
                        size = buffer->data + prz->buffer_size - block;
                numerr = persistent_ram_decode_rs8(prz, block, size, par);
                if (numerr > 0) {
                        pr_devel("persistent_ram: error in block %p, %d\n",
                               block, numerr);
                        prz->corrected_bytes += numerr;
                } else if (numerr < 0) {
                        pr_devel("persistent_ram: uncorrectable error in block %p\n",
                                block);
                        prz->bad_blocks++;
                }
                block += prz->ecc_info.block_size;
                par += prz->ecc_info.ecc_size;
        }
}

static int persistent_ram_init_ecc(struct persistent_ram_zone *prz,
                                   struct persistent_ram_ecc_info *ecc_info)
{
        int numerr;
        struct persistent_ram_buffer *buffer = prz->buffer;
        int ecc_blocks;
        size_t ecc_total;

        if (!ecc_info || !ecc_info->ecc_size)
                return 0;

        prz->ecc_info.block_size = ecc_info->block_size ?: 128;
        prz->ecc_info.ecc_size = ecc_info->ecc_size ?: 16;
        prz->ecc_info.symsize = ecc_info->symsize ?: 8;
        prz->ecc_info.poly = ecc_info->poly ?: 0x11d;

        ecc_blocks = DIV_ROUND_UP(prz->buffer_size - prz->ecc_info.ecc_size,
                                  prz->ecc_info.block_size +
                                  prz->ecc_info.ecc_size);
        ecc_total = (ecc_blocks + 1) * prz->ecc_info.ecc_size;
        if (ecc_total >= prz->buffer_size) {
                pr_err("%s: invalid ecc_size %u (total %zu, buffer size %zu)\n",
                       __func__, prz->ecc_info.ecc_size,
                       ecc_total, prz->buffer_size);
                return -EINVAL;
        }

        prz->buffer_size -= ecc_total;
        prz->par_buffer = buffer->data + prz->buffer_size;
        prz->par_header = prz->par_buffer +
                          ecc_blocks * prz->ecc_info.ecc_size;

        /*
         * first consecutive root is 0
         * primitive element to generate roots = 1
         */
        prz->rs_decoder = init_rs(prz->ecc_info.symsize, prz->ecc_info.poly,
                                  0, 1, prz->ecc_info.ecc_size);
        if (prz->rs_decoder == NULL) {
                pr_info("persistent_ram: init_rs failed\n");
                return -EINVAL;
        }

        prz->corrected_bytes = 0;
        prz->bad_blocks = 0;

        numerr = persistent_ram_decode_rs8(prz, buffer, sizeof(*buffer),
                                           prz->par_header);
        if (numerr > 0) {
                pr_info("persistent_ram: error in header, %d\n", numerr);
                prz->corrected_bytes += numerr;
        } else if (numerr < 0) {
                pr_info("persistent_ram: uncorrectable error in header\n");
                prz->bad_blocks++;
        }

        return 0;
}

ssize_t persistent_ram_ecc_string(struct persistent_ram_zone *prz,
        char *str, size_t len)
{
        ssize_t ret;

        if (!prz->ecc_info.ecc_size)
                return 0;

        if (prz->corrected_bytes || prz->bad_blocks)
                ret = snprintf(str, len, ""
                        "\n%d Corrected bytes, %d unrecoverable blocks\n",
                        prz->corrected_bytes, prz->bad_blocks);
        else
                ret = snprintf(str, len, "\nNo errors detected\n");

        return ret;
}

static void notrace persistent_ram_update(struct persistent_ram_zone *prz,
        const void *s, unsigned int start, unsigned int count)
{
        struct persistent_ram_buffer *buffer = prz->buffer;
        memcpy(buffer->data + start, s, count);
        persistent_ram_update_ecc(prz, start, count);
}

void persistent_ram_save_old(struct persistent_ram_zone *prz)
{
        struct persistent_ram_buffer *buffer = prz->buffer;
        size_t size = buffer_size(prz);
        size_t start = buffer_start(prz);

        if (!size)
                return;

        if (!prz->old_log) {
                persistent_ram_ecc_old(prz);
                prz->old_log = kmalloc(size, GFP_KERNEL);
        }
        if (!prz->old_log) {
                pr_err("persistent_ram: failed to allocate buffer\n");
                return;
        }

        prz->old_log_size = size;
        memcpy(prz->old_log, &buffer->data[start], size - start);
        memcpy(prz->old_log + size - start, &buffer->data[0], start);
}

int notrace persistent_ram_write(struct persistent_ram_zone *prz,
        const void *s, unsigned int count)
{
        int rem;
        int c = count;
        size_t start;

        if (unlikely(c > prz->buffer_size)) {
                s += c - prz->buffer_size;
                c = prz->buffer_size;
        }

        buffer_size_add(prz, c);

        start = buffer_start_add(prz, c);

        rem = prz->buffer_size - start;
        if (unlikely(rem < c)) {
                persistent_ram_update(prz, s, start, rem);
                s += rem;
                c -= rem;
                start = 0;
        }
        persistent_ram_update(prz, s, start, c);

        persistent_ram_update_header_ecc(prz);

        return count;
}

size_t persistent_ram_old_size(struct persistent_ram_zone *prz)
{
        return prz->old_log_size;
}

void *persistent_ram_old(struct persistent_ram_zone *prz)
{
        return prz->old_log;
}

void persistent_ram_free_old(struct persistent_ram_zone *prz)
{
        kfree(prz->old_log);
        prz->old_log = NULL;
        prz->old_log_size = 0;
}

void persistent_ram_zap(struct persistent_ram_zone *prz)
{
        atomic_set(&prz->buffer->start, 0);
        atomic_set(&prz->buffer->size, 0);
        persistent_ram_update_header_ecc(prz);
}

static void *persistent_ram_vmap(phys_addr_t start, size_t size)
{
        struct page **pages;
        phys_addr_t page_start;
        unsigned int page_count;
        pgprot_t prot;
        unsigned int i;
        void *vaddr;

        page_start = start - offset_in_page(start);
        page_count = DIV_ROUND_UP(size + offset_in_page(start), PAGE_SIZE);

        prot = pgprot_noncached(PAGE_KERNEL);

        pages = kmalloc(sizeof(struct page *) * page_count, GFP_KERNEL);
        if (!pages) {
                pr_err("%s: Failed to allocate array for %u pages\n", __func__,
                        page_count);
                return NULL;
        }

        for (i = 0; i < page_count; i++) {
                phys_addr_t addr = page_start + i * PAGE_SIZE;
                pages[i] = pfn_to_page(addr >> PAGE_SHIFT);
        }
        vaddr = vmap(pages, page_count, VM_MAP, prot);
        kfree(pages);

        return vaddr;
}

static void *persistent_ram_iomap(phys_addr_t start, size_t size)
{
        if (!request_mem_region(start, size, "persistent_ram")) {
                pr_err("request mem region (0x%llx@0x%llx) failed\n",
                        (unsigned long long)size, (unsigned long long)start);
                return NULL;
        }

        return ioremap(start, size);
}

static int persistent_ram_buffer_map(phys_addr_t start, phys_addr_t size,
                struct persistent_ram_zone *prz)
{
        prz->paddr = start;
        prz->size = size;

        if (pfn_valid(start >> PAGE_SHIFT))
                prz->vaddr = persistent_ram_vmap(start, size);
        else
                prz->vaddr = persistent_ram_iomap(start, size);

        if (!prz->vaddr) {
                pr_err("%s: Failed to map 0x%llx pages at 0x%llx\n", __func__,
                        (unsigned long long)size, (unsigned long long)start);
                return -ENOMEM;
        }

        prz->buffer = prz->vaddr + offset_in_page(start);
        prz->buffer_size = size - sizeof(struct persistent_ram_buffer);

        return 0;
}

static int persistent_ram_post_init(struct persistent_ram_zone *prz, u32 sig,
                                    struct persistent_ram_ecc_info *ecc_info)
{
        int ret;

        ret = persistent_ram_init_ecc(prz, ecc_info);
        if (ret)
                return ret;

        sig ^= PERSISTENT_RAM_SIG;

        if (prz->buffer->sig == sig) {
                if (buffer_size(prz) > prz->buffer_size ||
                    buffer_start(prz) > buffer_size(prz))
                        pr_info("persistent_ram: found existing invalid buffer,"
                                " size %zu, start %zu\n",
                               buffer_size(prz), buffer_start(prz));
                else {
                        pr_debug("persistent_ram: found existing buffer,"
                                " size %zu, start %zu\n",
                               buffer_size(prz), buffer_start(prz));
                        persistent_ram_save_old(prz);
                        return 0;
                }
        } else {
                pr_debug("persistent_ram: no valid data in buffer"
                        " (sig = 0x%08x)\n", prz->buffer->sig);
        }

        prz->buffer->sig = sig;
        persistent_ram_zap(prz);

        return 0;
}

void persistent_ram_free(struct persistent_ram_zone *prz)
{
        if (!prz)
                return;

        if (prz->vaddr) {
                if (pfn_valid(prz->paddr >> PAGE_SHIFT)) {
                        vunmap(prz->vaddr);
                } else {
                        iounmap(prz->vaddr);
                        release_mem_region(prz->paddr, prz->size);
                }
                prz->vaddr = NULL;
        }
        persistent_ram_free_old(prz);
        kfree(prz);
}

struct persistent_ram_zone *persistent_ram_new(phys_addr_t start, size_t size,
                        u32 sig, struct persistent_ram_ecc_info *ecc_info)
{
        struct persistent_ram_zone *prz;
        int ret = -ENOMEM;

        prz = kzalloc(sizeof(struct persistent_ram_zone), GFP_KERNEL);
        if (!prz) {
                pr_err("persistent_ram: failed to allocate persistent ram zone\n");
                goto err;
        }

        ret = persistent_ram_buffer_map(start, size, prz);
        if (ret)
                goto err;

        ret = persistent_ram_post_init(prz, sig, ecc_info);
        if (ret)
                goto err;

        return prz;
err:
        persistent_ram_free(prz);
        return ERR_PTR(ret);
}