/*
 * (C) Copyright IBM Deutschland Entwicklung GmbH 2006
 *
 * Author: Maxim Shchetynin <maxim@de.ibm.com>
 *
 * Axon DDR2 device driver.
 * It registers one block device per Axon's DDR2 memory bank found on a system.
 * Block devices are called axonram?, their major and minor numbers are
 * available in /proc/devices, /proc/partitions or in /sys/block/axonram?/dev.
 *
 * 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, 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., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

#include <linux/bio.h>
#include <linux/blkdev.h>
#include <linux/dax.h>
#include <linux/device.h>
#include <linux/errno.h>
#include <linux/fs.h>
#include <linux/genhd.h>
#include <linux/interrupt.h>
#include <linux/io.h>
#include <linux/ioport.h>
#include <linux/irq.h>
#include <linux/irqreturn.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/mod_devicetable.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/string.h>
#include <linux/types.h>
#include <linux/of_device.h>
#include <linux/of_platform.h>
#include <linux/pfn_t.h>
#include <linux/uio.h>

#include <asm/page.h>
#include <asm/prom.h>

#define AXON_RAM_MODULE_NAME		"axonram"
#define AXON_RAM_DEVICE_NAME		"axonram"
#define AXON_RAM_MINORS_PER_DISK	16
#define AXON_RAM_BLOCK_SHIFT		PAGE_SHIFT
#define AXON_RAM_BLOCK_SIZE		1 << AXON_RAM_BLOCK_SHIFT
#define AXON_RAM_SECTOR_SHIFT		9
#define AXON_RAM_SECTOR_SIZE		1 << AXON_RAM_SECTOR_SHIFT
#define AXON_RAM_IRQ_FLAGS		IRQF_SHARED | IRQF_TRIGGER_RISING

static int azfs_major, azfs_minor;

struct axon_ram_bank {
	struct platform_device	*device;
	struct gendisk		*disk;
	struct dax_device	*dax_dev;
	unsigned int		irq_id;
	unsigned long		ph_addr;
	unsigned long		io_addr;
	unsigned long		size;
	unsigned long		ecc_counter;
};

static ssize_t
axon_ram_sysfs_ecc(struct device *dev, struct device_attribute *attr, char *buf)
{
	struct platform_device *device = to_platform_device(dev);
	struct axon_ram_bank *bank = device->dev.platform_data;

	BUG_ON(!bank);

	return sprintf(buf, "%ld\n", bank->ecc_counter);
}

static DEVICE_ATTR(ecc, S_IRUGO, axon_ram_sysfs_ecc, NULL);

/**
 * axon_ram_irq_handler - interrupt handler for Axon RAM ECC
 * @irq: interrupt ID
 * @dev: pointer to of_device
 */
static irqreturn_t
axon_ram_irq_handler(int irq, void *dev)
{
	struct platform_device *device = dev;
	struct axon_ram_bank *bank = device->dev.platform_data;

	BUG_ON(!bank);

	dev_err(&device->dev, "Correctable memory error occurred\n");
	bank->ecc_counter++;
	return IRQ_HANDLED;
}

/**
 * axon_ram_make_request - make_request() method for block device
 * @queue, @bio: see blk_queue_make_request()
 */
static blk_qc_t
axon_ram_make_request(struct request_queue *queue, struct bio *bio)
{
	struct axon_ram_bank *bank = bio->bi_disk->private_data;
	unsigned long phys_mem, phys_end;
	void *user_mem;
	struct bio_vec vec;
	unsigned int transfered;
	struct bvec_iter iter;

	phys_mem = bank->io_addr + (bio->bi_iter.bi_sector <<
				    AXON_RAM_SECTOR_SHIFT);
	phys_end = bank->io_addr + bank->size;
	transfered = 0;
	bio_for_each_segment(vec, bio, iter) {
		if (unlikely(phys_mem + vec.bv_len > phys_end)) {
			bio_io_error(bio);
			return BLK_QC_T_NONE;
		}

		user_mem = page_address(vec.bv_page) + vec.bv_offset;
		if (bio_data_dir(bio) == READ)
			memcpy(user_mem, (void *) phys_mem, vec.bv_len);
		else
			memcpy((void *) phys_mem, user_mem, vec.bv_len);

		phys_mem += vec.bv_len;
		transfered += vec.bv_len;
	}
	bio_endio(bio);
	return BLK_QC_T_NONE;
}

static const struct block_device_operations axon_ram_devops = {
	.owner		= THIS_MODULE,
};

static long
__axon_ram_direct_access(struct axon_ram_bank *bank, pgoff_t pgoff, long nr_pages,
		       void **kaddr, pfn_t *pfn)
{
	resource_size_t offset = pgoff * PAGE_SIZE;

	*kaddr = (void *) bank->io_addr + offset;
	*pfn = phys_to_pfn_t(bank->ph_addr + offset, PFN_DEV);
	return (bank->size - offset) / PAGE_SIZE;
}

static long
axon_ram_dax_direct_access(struct dax_device *dax_dev, pgoff_t pgoff, long nr_pages,
		       void **kaddr, pfn_t *pfn)
{
	struct axon_ram_bank *bank = dax_get_private(dax_dev);

	return __axon_ram_direct_access(bank, pgoff, nr_pages, kaddr, pfn);
}

static size_t axon_ram_copy_from_iter(struct dax_device *dax_dev, pgoff_t pgoff,
		void *addr, size_t bytes, struct iov_iter *i)
{
	return copy_from_iter(addr, bytes, i);
}

static const struct dax_operations axon_ram_dax_ops = {
	.direct_access = axon_ram_dax_direct_access,
	.copy_from_iter = axon_ram_copy_from_iter,
};

/**
 * axon_ram_probe - probe() method for platform driver
 * @device: see platform_driver method
 */
static int axon_ram_probe(struct platform_device *device)
{
	static int axon_ram_bank_id = -1;
	struct axon_ram_bank *bank;
	struct resource resource;
	int rc;

	axon_ram_bank_id++;

	dev_info(&device->dev, "Found memory controller on %pOF\n",
			device->dev.of_node);

	bank = kzalloc(sizeof(*bank), GFP_KERNEL);
	if (!bank)
		return -ENOMEM;

	device->dev.platform_data = bank;

	bank->device = device;

	if (of_address_to_resource(device->dev.of_node, 0, &resource) != 0) {
		dev_err(&device->dev, "Cannot access device tree\n");
		rc = -EFAULT;
		goto failed;
	}

	bank->size = resource_size(&resource);

	if (bank->size == 0) {
		dev_err(&device->dev, "No DDR2 memory found for %s%d\n",
				AXON_RAM_DEVICE_NAME, axon_ram_bank_id);
		rc = -ENODEV;
		goto failed;
	}

	dev_info(&device->dev, "Register DDR2 memory device %s%d with %luMB\n",
			AXON_RAM_DEVICE_NAME, axon_ram_bank_id, bank->size >> 20);

	bank->ph_addr = resource.start;
	bank->io_addr = (unsigned long) ioremap_prot(
			bank->ph_addr, bank->size, _PAGE_NO_CACHE);
	if (bank->io_addr == 0) {
		dev_err(&device->dev, "ioremap() failed\n");
		rc = -EFAULT;
		goto failed;
	}

	bank->disk = alloc_disk(AXON_RAM_MINORS_PER_DISK);
	if (bank->disk == NULL) {
		dev_err(&device->dev, "Cannot register disk\n");
		rc = -EFAULT;
		goto failed;
	}


	bank->disk->major = azfs_major;
	bank->disk->first_minor = azfs_minor;
	bank->disk->fops = &axon_ram_devops;
	bank->disk->private_data = bank;

	sprintf(bank->disk->disk_name, "%s%d",
			AXON_RAM_DEVICE_NAME, axon_ram_bank_id);

	bank->dax_dev = alloc_dax(bank, bank->disk->disk_name,
			&axon_ram_dax_ops);
	if (!bank->dax_dev) {
		rc = -ENOMEM;
		goto failed;
	}

	bank->disk->queue = blk_alloc_queue(GFP_KERNEL);
	if (bank->disk->queue == NULL) {
		dev_err(&device->dev, "Cannot register disk queue\n");
		rc = -EFAULT;
		goto failed;
	}

	set_capacity(bank->disk, bank->size >> AXON_RAM_SECTOR_SHIFT);
	blk_queue_make_request(bank->disk->queue, axon_ram_make_request);
	blk_queue_logical_block_size(bank->disk->queue, AXON_RAM_SECTOR_SIZE);
	device_add_disk(&device->dev, bank->disk);

	bank->irq_id = irq_of_parse_and_map(device->dev.of_node, 0);
	if (!bank->irq_id) {
		dev_err(&device->dev, "Cannot access ECC interrupt ID\n");
		rc = -EFAULT;
		goto failed;
	}

	rc = request_irq(bank->irq_id, axon_ram_irq_handler,
			AXON_RAM_IRQ_FLAGS, bank->disk->disk_name, device);
	if (rc != 0) {
		dev_err(&device->dev, "Cannot register ECC interrupt handler\n");
		bank->irq_id = 0;
		rc = -EFAULT;
		goto failed;
	}

	rc = device_create_file(&device->dev, &dev_attr_ecc);
	if (rc != 0) {
		dev_err(&device->dev, "Cannot create sysfs file\n");
		rc = -EFAULT;
		goto failed;
	}

	azfs_minor += bank->disk->minors;

	return 0;

failed:
	if (bank->irq_id)
		free_irq(bank->irq_id, device);
	if (bank->disk != NULL) {
		if (bank->disk->major > 0)
			unregister_blkdev(bank->disk->major,
					bank->disk->disk_name);
		if (bank->disk->flags & GENHD_FL_UP)
			del_gendisk(bank->disk);
		put_disk(bank->disk);
	}
	kill_dax(bank->dax_dev);
	put_dax(bank->dax_dev);
	device->dev.platform_data = NULL;
	if (bank->io_addr != 0)
		iounmap((void __iomem *) bank->io_addr);
	kfree(bank);
	return rc;
}

/**
 * axon_ram_remove - remove() method for platform driver
 * @device: see of_platform_driver method
 */
static int
axon_ram_remove(struct platform_device *device)
{
	struct axon_ram_bank *bank = device->dev.platform_data;

	BUG_ON(!bank || !bank->disk);

	device_remove_file(&device->dev, &dev_attr_ecc);
	free_irq(bank->irq_id, device);
	kill_dax(bank->dax_dev);
	put_dax(bank->dax_dev);
	del_gendisk(bank->disk);
	put_disk(bank->disk);
	iounmap((void __iomem *) bank->io_addr);
	kfree(bank);

	return 0;
}

static const struct of_device_id axon_ram_device_id[] = {
	{
		.type	= "dma-memory"
	},
	{}
};
MODULE_DEVICE_TABLE(of, axon_ram_device_id);

static struct platform_driver axon_ram_driver = {
	.probe		= axon_ram_probe,
	.remove		= axon_ram_remove,
	.driver = {
		.name = AXON_RAM_MODULE_NAME,
		.of_match_table = axon_ram_device_id,
	},
};

/**
 * axon_ram_init
 */
static int __init
axon_ram_init(void)
{
	azfs_major = register_blkdev(azfs_major, AXON_RAM_DEVICE_NAME);
	if (azfs_major < 0) {
		printk(KERN_ERR "%s cannot become block device major number\n",
				AXON_RAM_MODULE_NAME);
		return -EFAULT;
	}
	azfs_minor = 0;

	return platform_driver_register(&axon_ram_driver);
}

/**
 * axon_ram_exit
 */
static void __exit
axon_ram_exit(void)
{
	platform_driver_unregister(&axon_ram_driver);
	unregister_blkdev(azfs_major, AXON_RAM_DEVICE_NAME);
}

module_init(axon_ram_init);
module_exit(axon_ram_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Maxim Shchetynin <maxim@de.ibm.com>");
MODULE_DESCRIPTION("Axon DDR2 RAM device driver for IBM Cell BE");