/*
   * Xpram.c -- the S/390 expanded memory RAM-disk
   *           
   * significant parts of this code are based on
   * the sbull device driver presented in
   * A. Rubini: Linux Device Drivers
   *
   * Author of XPRAM specific coding: Reinhard Buendgen
   *                                  buendgen@de.ibm.com
   * Rewrite for 2.5: Martin Schwidefsky <schwidefsky@de.ibm.com>
   *
   * External interfaces:
   *   Interfaces to linux kernel
   *        xpram_setup: read kernel parameters
   *   Device specific file operations
   *        xpram_iotcl
   *        xpram_open
   *
   * "ad-hoc" partitioning:
   *    the expanded memory can be partitioned among several devices 
   *    (with different minors). The partitioning set up can be
   *    set by kernel or module parameters (int devs & int sizes[])
   *
   * Potential future improvements:
   *   generic hard disk support to replace ad-hoc partitioning
   */
  
  #define KMSG_COMPONENT "xpram"
  #define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
  
  #include <linux/module.h>
  #include <linux/moduleparam.h>
  #include <linux/ctype.h>  /* isdigit, isxdigit */
  #include <linux/errno.h>
  #include <linux/init.h>
  #include <linux/blkdev.h>
  #include <linux/blkpg.h>
  #include <linux/hdreg.h>  /* HDIO_GETGEO */
  #include <linux/device.h>
  #include <linux/bio.h>
  #include <linux/suspend.h>
  #include <linux/platform_device.h>
  #include <linux/gfp.h>
  #include <asm/uaccess.h>
  
  #define XPRAM_NAME	"xpram"
  #define XPRAM_DEVS	1	/* one partition */
  #define XPRAM_MAX_DEVS	32	/* maximal number of devices (partitions) */
  
  typedef struct {
  	unsigned int	size;		/* size of xpram segment in pages */
  	unsigned int	offset;		/* start page of xpram segment */
  } xpram_device_t;
  
  static xpram_device_t xpram_devices[XPRAM_MAX_DEVS];
  static unsigned int xpram_sizes[XPRAM_MAX_DEVS];
  static struct gendisk *xpram_disks[XPRAM_MAX_DEVS];
  static struct request_queue *xpram_queues[XPRAM_MAX_DEVS];
  static unsigned int xpram_pages;
  static int xpram_devs;
  
  /*
   * Parameter parsing functions.
   */
  static int devs = XPRAM_DEVS;
  static char *sizes[XPRAM_MAX_DEVS];
  
  module_param(devs, int, 0);
  module_param_array(sizes, charp, NULL, 0);
  
  MODULE_PARM_DESC(devs, "number of devices (\"partitions\"), " \
  		 "the default is " __MODULE_STRING(XPRAM_DEVS) "
  ");
  MODULE_PARM_DESC(sizes, "list of device (partition) sizes " \
  		 "the defaults are 0s 
  " \
  		 "All devices with size 0 equally partition the "
  		 "remaining space on the expanded strorage not "
  		 "claimed by explicit sizes
  ");
  MODULE_LICENSE("GPL");
  
  /*
   * Copy expanded memory page (4kB) into main memory                  
   * Arguments                                                         
   *           page_addr:    address of target page                    
   *           xpage_index:  index of expandeded memory page           
   * Return value                                                      
   *           0:            if operation succeeds
   *           -EIO:         if pgin failed
   *           -ENXIO:       if xpram has vanished
   */
  static int xpram_page_in (unsigned long page_addr, unsigned int xpage_index)
  {
  	int cc = 2;	/* return unused cc 2 if pgin traps */
  
  	asm volatile(
  		"	.insn	rre,0xb22e0000,%1,%2
  "  /* pgin %1,%2 */
  		"0:	ipm	%0
  "
  		"	srl	%0,28
  "
  		"1:
  "
  		EX_TABLE(0b,1b)
  		: "+d" (cc) : "a" (__pa(page_addr)), "d" (xpage_index) : "cc");
  	if (cc == 3)
  		return -ENXIO;
  	if (cc == 2)
  		return -ENXIO;
  	if (cc == 1)
  		return -EIO;
  	return 0;
  }
  
  /*
   * Copy a 4kB page of main memory to an expanded memory page          
   * Arguments                                                          
   *           page_addr:    address of source page                     
   *           xpage_index:  index of expandeded memory page            
   * Return value                                                       
   *           0:            if operation succeeds
   *           -EIO:         if pgout failed
   *           -ENXIO:       if xpram has vanished
   */
  static long xpram_page_out (unsigned long page_addr, unsigned int xpage_index)
  {
  	int cc = 2;	/* return unused cc 2 if pgin traps */
  
  	asm volatile(
  		"	.insn	rre,0xb22f0000,%1,%2
  "  /* pgout %1,%2 */
  		"0:	ipm	%0
  "
  		"	srl	%0,28
  "
  		"1:
  "
  		EX_TABLE(0b,1b)
  		: "+d" (cc) : "a" (__pa(page_addr)), "d" (xpage_index) : "cc");
  	if (cc == 3)
  		return -ENXIO;
  	if (cc == 2)
  		return -ENXIO;
  	if (cc == 1)
  		return -EIO;
  	return 0;
  }
  
  /*
   * Check if xpram is available.
   */
  static int xpram_present(void)
  {
  	unsigned long mem_page;
  	int rc;
  
  	mem_page = (unsigned long) __get_free_page(GFP_KERNEL);
  	if (!mem_page)
  		return -ENOMEM;
  	rc = xpram_page_in(mem_page, 0);
  	free_page(mem_page);
  	return rc ? -ENXIO : 0;
  }
  
  /*
   * Return index of the last available xpram page.
   */
  static unsigned long xpram_highest_page_index(void)
  {
  	unsigned int page_index, add_bit;
  	unsigned long mem_page;
  
  	mem_page = (unsigned long) __get_free_page(GFP_KERNEL);
  	if (!mem_page)
  		return 0;
  
  	page_index = 0;
  	add_bit = 1ULL << (sizeof(unsigned int)*8 - 1);
  	while (add_bit > 0) {
  		if (xpram_page_in(mem_page, page_index | add_bit) == 0)
  			page_index |= add_bit;
  		add_bit >>= 1;
  	}
  
  	free_page (mem_page);
  
  	return page_index;
  }
  
  /*
   * Block device make request function.
   */
  static void xpram_make_request(struct request_queue *q, struct bio *bio)
  {
  	xpram_device_t *xdev = bio->bi_bdev->bd_disk->private_data;
  	struct bio_vec bvec;
  	struct bvec_iter iter;
  	unsigned int index;
  	unsigned long page_addr;
  	unsigned long bytes;
  
  	if ((bio->bi_iter.bi_sector & 7) != 0 ||
  	    (bio->bi_iter.bi_size & 4095) != 0)
  		/* Request is not page-aligned. */
  		goto fail;
  	if ((bio->bi_iter.bi_size >> 12) > xdev->size)
  		/* Request size is no page-aligned. */
  		goto fail;
  	if ((bio->bi_iter.bi_sector >> 3) > 0xffffffffU - xdev->offset)
  		goto fail;
  	index = (bio->bi_iter.bi_sector >> 3) + xdev->offset;
  	bio_for_each_segment(bvec, bio, iter) {
  		page_addr = (unsigned long)
  			kmap(bvec.bv_page) + bvec.bv_offset;
  		bytes = bvec.bv_len;
  		if ((page_addr & 4095) != 0 || (bytes & 4095) != 0)
  			/* More paranoia. */
  			goto fail;
  		while (bytes > 0) {
  			if (bio_data_dir(bio) == READ) {
  				if (xpram_page_in(page_addr, index) != 0)
  					goto fail;
  			} else {
  				if (xpram_page_out(page_addr, index) != 0)
  					goto fail;
  			}
  			page_addr += 4096;
  			bytes -= 4096;
  			index++;
  		}
  	}
  	set_bit(BIO_UPTODATE, &bio->bi_flags);
  	bio_endio(bio, 0);
  	return;
  fail:
  	bio_io_error(bio);
  }
  
  static int xpram_getgeo(struct block_device *bdev, struct hd_geometry *geo)
  {
  	unsigned long size;
  
  	/*
  	 * get geometry: we have to fake one...  trim the size to a
  	 * multiple of 64 (32k): tell we have 16 sectors, 4 heads,
  	 * whatever cylinders. Tell also that data starts at sector. 4.
  	 */
  	size = (xpram_pages * 8) & ~0x3f;
  	geo->cylinders = size >> 6;
  	geo->heads = 4;
  	geo->sectors = 16;
  	geo->start = 4;
  	return 0;
  }
  
  static const struct block_device_operations xpram_devops =
  {
  	.owner	= THIS_MODULE,
  	.getgeo	= xpram_getgeo,
  };
  
  /*
   * Setup xpram_sizes array.
   */
  static int __init xpram_setup_sizes(unsigned long pages)
  {
  	unsigned long mem_needed;
  	unsigned long mem_auto;
  	unsigned long long size;
  	char *sizes_end;
  	int mem_auto_no;
  	int i;
  
  	/* Check number of devices. */
  	if (devs <= 0 || devs > XPRAM_MAX_DEVS) {
  		pr_err("%d is not a valid number of XPRAM devices
  ",devs);
  		return -EINVAL;
  	}
  	xpram_devs = devs;
  
  	/*
  	 * Copy sizes array to xpram_sizes and align partition
  	 * sizes to page boundary.
  	 */
  	mem_needed = 0;
  	mem_auto_no = 0;
  	for (i = 0; i < xpram_devs; i++) {
  		if (sizes[i]) {
  			size = simple_strtoull(sizes[i], &sizes_end, 0);
  			switch (*sizes_end) {
  			case 'g':
  			case 'G':
  				size <<= 20;
  				break;
  			case 'm':
  			case 'M':
  				size <<= 10;
  			}
  			xpram_sizes[i] = (size + 3) & -4UL;
  		}
  		if (xpram_sizes[i])
  			mem_needed += xpram_sizes[i];
  		else
  			mem_auto_no++;
  	}
  	
  	pr_info("  number of devices (partitions): %d 
  ", xpram_devs);
  	for (i = 0; i < xpram_devs; i++) {
  		if (xpram_sizes[i])
  			pr_info("  size of partition %d: %u kB
  ",
  				i, xpram_sizes[i]);
  		else
  			pr_info("  size of partition %d to be set "
  				"automatically
  ",i);
  	}
  	pr_info("  memory needed (for sized partitions): %lu kB
  ",
  		mem_needed);
  	pr_info("  partitions to be sized automatically: %d
  ",
  		mem_auto_no);
  
  	if (mem_needed > pages * 4) {
  		pr_err("Not enough expanded memory available
  ");
  		return -EINVAL;
  	}
  
  	/*
  	 * partitioning:
  	 * xpram_sizes[i] != 0; partition i has size xpram_sizes[i] kB
  	 * else:             ; all partitions with zero xpram_sizes[i]
  	 *                     partition equally the remaining space
  	 */
  	if (mem_auto_no) {
  		mem_auto = ((pages - mem_needed / 4) / mem_auto_no) * 4;
  		pr_info("  automatically determined "
  			"partition size: %lu kB
  ", mem_auto);
  		for (i = 0; i < xpram_devs; i++)
  			if (xpram_sizes[i] == 0)
  				xpram_sizes[i] = mem_auto;
  	}
  	return 0;
  }
  
  static int __init xpram_setup_blkdev(void)
  {
  	unsigned long offset;
  	int i, rc = -ENOMEM;
  
  	for (i = 0; i < xpram_devs; i++) {
  		xpram_disks[i] = alloc_disk(1);
  		if (!xpram_disks[i])
  			goto out;
  		xpram_queues[i] = blk_alloc_queue(GFP_KERNEL);
  		if (!xpram_queues[i]) {
  			put_disk(xpram_disks[i]);
  			goto out;
  		}
  		queue_flag_set_unlocked(QUEUE_FLAG_NONROT, xpram_queues[i]);
  		blk_queue_make_request(xpram_queues[i], xpram_make_request);
  		blk_queue_logical_block_size(xpram_queues[i], 4096);
  	}
  
  	/*
  	 * Register xpram major.
  	 */
  	rc = register_blkdev(XPRAM_MAJOR, XPRAM_NAME);
  	if (rc < 0)
  		goto out;
  
  	/*
  	 * Setup device structures.
  	 */
  	offset = 0;
  	for (i = 0; i < xpram_devs; i++) {
  		struct gendisk *disk = xpram_disks[i];
  
  		xpram_devices[i].size = xpram_sizes[i] / 4;
  		xpram_devices[i].offset = offset;
  		offset += xpram_devices[i].size;
  		disk->major = XPRAM_MAJOR;
  		disk->first_minor = i;
  		disk->fops = &xpram_devops;
  		disk->private_data = &xpram_devices[i];
  		disk->queue = xpram_queues[i];
  		sprintf(disk->disk_name, "slram%d", i);
  		set_capacity(disk, xpram_sizes[i] << 1);
  		add_disk(disk);
  	}
  
  	return 0;
  out:
  	while (i--) {
  		blk_cleanup_queue(xpram_queues[i]);
  		put_disk(xpram_disks[i]);
  	}
  	return rc;
  }
  
  /*
   * Resume failed: Print error message and call panic.
   */
  static void xpram_resume_error(const char *message)
  {
  	pr_err("Resuming the system failed: %s
  ", message);
  	panic("xpram resume error
  ");
  }
  
  /*
   * Check if xpram setup changed between suspend and resume.
   */
  static int xpram_restore(struct device *dev)
  {
  	if (!xpram_pages)
  		return 0;
  	if (xpram_present() != 0)
  		xpram_resume_error("xpram disappeared");
  	if (xpram_pages != xpram_highest_page_index() + 1)
  		xpram_resume_error("Size of xpram changed");
  	return 0;
  }
  
  static const struct dev_pm_ops xpram_pm_ops = {
  	.restore	= xpram_restore,
  };
  
  static struct platform_driver xpram_pdrv = {
  	.driver = {
  		.name	= XPRAM_NAME,
  		.owner	= THIS_MODULE,
  		.pm	= &xpram_pm_ops,
  	},
  };
  
  static struct platform_device *xpram_pdev;
  
  /*
   * Finally, the init/exit functions.
   */
  static void __exit xpram_exit(void)
  {
  	int i;
  	for (i = 0; i < xpram_devs; i++) {
  		del_gendisk(xpram_disks[i]);
  		blk_cleanup_queue(xpram_queues[i]);
  		put_disk(xpram_disks[i]);
  	}
  	unregister_blkdev(XPRAM_MAJOR, XPRAM_NAME);
  	platform_device_unregister(xpram_pdev);
  	platform_driver_unregister(&xpram_pdrv);
  }
  
  static int __init xpram_init(void)
  {
  	int rc;
  
  	/* Find out size of expanded memory. */
  	if (xpram_present() != 0) {
  		pr_err("No expanded memory available
  ");
  		return -ENODEV;
  	}
  	xpram_pages = xpram_highest_page_index() + 1;
  	pr_info("  %u pages expanded memory found (%lu KB).
  ",
  		xpram_pages, (unsigned long) xpram_pages*4);
  	rc = xpram_setup_sizes(xpram_pages);
  	if (rc)
  		return rc;
  	rc = platform_driver_register(&xpram_pdrv);
  	if (rc)
  		return rc;
  	xpram_pdev = platform_device_register_simple(XPRAM_NAME, -1, NULL, 0);
  	if (IS_ERR(xpram_pdev)) {
  		rc = PTR_ERR(xpram_pdev);
  		goto fail_platform_driver_unregister;
  	}
  	rc = xpram_setup_blkdev();
  	if (rc)
  		goto fail_platform_device_unregister;
  	return 0;
  
  fail_platform_device_unregister:
  	platform_device_unregister(xpram_pdev);
  fail_platform_driver_unregister:
  	platform_driver_unregister(&xpram_pdrv);
  	return rc;
  }
  
  module_init(xpram_init);
  module_exit(xpram_exit);