/*
 * Generic on-chip SRAM allocation driver
 *
 * Copyright (C) 2012 Philipp Zabel, Pengutronix
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 * 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.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
 * MA 02110-1301, USA.
 */

#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/clk.h>
#include <linux/err.h>
#include <linux/io.h>
#include <linux/of.h>
#include <linux/of_address.h>
#include <linux/list.h>
#include <linux/list_sort.h>
#include <linux/platform_device.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/genalloc.h>

#define SRAM_GRANULARITY        32

struct sram_dev {
        struct gen_pool *pool;
        struct clk *clk;
};

struct sram_reserve {
        struct list_head list;
        u32 start;
        u32 size;
};

static int sram_reserve_cmp(void *priv, struct list_head *a,
                                        struct list_head *b)
{
        struct sram_reserve *ra = list_entry(a, struct sram_reserve, list);
        struct sram_reserve *rb = list_entry(b, struct sram_reserve, list);

        return ra->start - rb->start;
}

static int sram_probe(struct platform_device *pdev)
{
        void __iomem *virt_base;
        struct sram_dev *sram;
        struct resource *res;
        struct device_node *np = pdev->dev.of_node, *child;
        unsigned long size, cur_start, cur_size;
        struct sram_reserve *rblocks, *block;
        struct list_head reserve_list;
        unsigned int nblocks;
        int ret;

        INIT_LIST_HEAD(&reserve_list);

        res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
        virt_base = devm_ioremap_resource(&pdev->dev, res);
        if (IS_ERR(virt_base))
                return PTR_ERR(virt_base);

        size = resource_size(res);

        sram = devm_kzalloc(&pdev->dev, sizeof(*sram), GFP_KERNEL);
        if (!sram)
                return -ENOMEM;

        sram->clk = devm_clk_get(&pdev->dev, NULL);
        if (IS_ERR(sram->clk))
                sram->clk = NULL;
        else
                clk_prepare_enable(sram->clk);

        sram->pool = devm_gen_pool_create(&pdev->dev, ilog2(SRAM_GRANULARITY), -1);
        if (!sram->pool)
                return -ENOMEM;

        /*
         * We need an additional block to mark the end of the memory region
         * after the reserved blocks from the dt are processed.
         */
        nblocks = (np) ? of_get_available_child_count(np) + 1 : 1;
        rblocks = kmalloc((nblocks) * sizeof(*rblocks), GFP_KERNEL);
        if (!rblocks) {
                ret = -ENOMEM;
                goto err_alloc;
        }

        block = &rblocks[0];
        for_each_available_child_of_node(np, child) {
                struct resource child_res;

                ret = of_address_to_resource(child, 0, &child_res);
                if (ret < 0) {
                        dev_err(&pdev->dev,
                                "could not get address for node %s\n",
                                child->full_name);
                        goto err_chunks;
                }

                if (child_res.start < res->start || child_res.end > res->end) {
                        dev_err(&pdev->dev,
                                "reserved block %s outside the sram area\n",
                                child->full_name);
                        ret = -EINVAL;
                        goto err_chunks;
                }

                block->start = child_res.start - res->start;
                block->size = resource_size(&child_res);
                list_add_tail(&block->list, &reserve_list);

                dev_dbg(&pdev->dev, "found reserved block 0x%x-0x%x\n",
                        block->start,
                        block->start + block->size);

                block++;
        }

        /* the last chunk marks the end of the region */
        rblocks[nblocks - 1].start = size;
        rblocks[nblocks - 1].size = 0;
        list_add_tail(&rblocks[nblocks - 1].list, &reserve_list);

        list_sort(NULL, &reserve_list, sram_reserve_cmp);

        cur_start = 0;

        list_for_each_entry(block, &reserve_list, list) {
                /* can only happen if sections overlap */
                if (block->start < cur_start) {
                        dev_err(&pdev->dev,
                                "block at 0x%x starts after current offset 0x%lx\n",
                                block->start, cur_start);
                        ret = -EINVAL;
                        goto err_chunks;
                }

                /* current start is in a reserved block, so continue after it */
                if (block->start == cur_start) {
                        cur_start = block->start + block->size;
                        continue;
                }

                /*
                 * allocate the space between the current starting
                 * address and the following reserved block, or the
                 * end of the region.
                 */
                cur_size = block->start - cur_start;

                dev_dbg(&pdev->dev, "adding chunk 0x%lx-0x%lx\n",
                        cur_start, cur_start + cur_size);
                ret = gen_pool_add_virt(sram->pool,
                                (unsigned long)virt_base + cur_start,
                                res->start + cur_start, cur_size, -1);
                if (ret < 0)
                        goto err_chunks;

                /* next allocation after this reserved block */
                cur_start = block->start + block->size;
        }

        kfree(rblocks);

        platform_set_drvdata(pdev, sram);

        dev_dbg(&pdev->dev, "SRAM pool: %ld KiB @ 0x%p\n", size / 1024, virt_base);

        return 0;

err_chunks:
        kfree(rblocks);
err_alloc:
        if (sram->clk)
                clk_disable_unprepare(sram->clk);
        return ret;
}

static int sram_remove(struct platform_device *pdev)
{
        struct sram_dev *sram = platform_get_drvdata(pdev);

        if (gen_pool_avail(sram->pool) < gen_pool_size(sram->pool))
                dev_dbg(&pdev->dev, "removed while SRAM allocated\n");

        if (sram->clk)
                clk_disable_unprepare(sram->clk);

        return 0;
}

#ifdef CONFIG_OF
static struct of_device_id sram_dt_ids[] = {
        { .compatible = "mmio-sram" },
        {}
};
#endif

static struct platform_driver sram_driver = {
        .driver = {
                .name = "sram",
                .of_match_table = of_match_ptr(sram_dt_ids),
        },
        .probe = sram_probe,
        .remove = sram_remove,
};

static int __init sram_init(void)
{
        return platform_driver_register(&sram_driver);
}

postcore_initcall(sram_init);