Free Electrons

Embedded Linux Experts

  1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
/*
 * 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
 */

#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/ctype.h>  /* isdigit, isxdigit */
#include <linux/errno.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/blkdev.h>
#include <linux/blkpg.h>
#include <linux/hdreg.h>  /* HDIO_GETGEO */
#include <linux/sysdev.h>
#include <linux/bio.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) */

#define PRINT_DEBUG(x...)	printk(KERN_DEBUG XPRAM_NAME " debug:" x)
#define PRINT_INFO(x...)	printk(KERN_INFO XPRAM_NAME " info:" x)
#define PRINT_WARN(x...)	printk(KERN_WARNING XPRAM_NAME " warning:" x)
#define PRINT_ERR(x...)		printk(KERN_ERR XPRAM_NAME " error:" x)


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 unsigned int xpram_pages;
static int xpram_devs;

/*
 * Parameter parsing functions.
 */
static int __initdata devs = XPRAM_DEVS;
static char __initdata *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) "\n");
MODULE_PARM_DESC(sizes, "list of device (partition) sizes " \
		 "the defaults are 0s \n" \
		 "All devices with size 0 equally partition the "
		 "remaining space on the expanded strorage not "
		 "claimed by explicit sizes\n");
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\n"  /* pgin %1,%2 */
		"0:	ipm	%0\n"
		"	srl	%0,28\n"
		"1:\n"
		EX_TABLE(0b,1b)
		: "+d" (cc) : "a" (__pa(page_addr)), "d" (xpage_index) : "cc");
	if (cc == 3)
		return -ENXIO;
	if (cc == 2) {
		PRINT_ERR("expanded storage lost!\n");
		return -ENXIO;
	}
	if (cc == 1) {
		PRINT_ERR("page in failed for page index %u.\n",
			  xpage_index);
		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\n"  /* pgout %1,%2 */
		"0:	ipm	%0\n"
		"	srl	%0,28\n"
		"1:\n"
		EX_TABLE(0b,1b)
		: "+d" (cc) : "a" (__pa(page_addr)), "d" (xpage_index) : "cc");
	if (cc == 3)
		return -ENXIO;
	if (cc == 2) {
		PRINT_ERR("expanded storage lost!\n");
		return -ENXIO;
	}
	if (cc == 1) {
		PRINT_ERR("page out failed for page index %u.\n",
			  xpage_index);
		return -EIO;
	}
	return 0;
}

/*
 * Check if xpram is available.
 */
static int __init 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 __init 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 int 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;
	unsigned int index;
	unsigned long page_addr;
	unsigned long bytes;
	int i;

	if ((bio->bi_sector & 7) != 0 || (bio->bi_size & 4095) != 0)
		/* Request is not page-aligned. */
		goto fail;
	if ((bio->bi_size >> 12) > xdev->size)
		/* Request size is no page-aligned. */
		goto fail;
	if ((bio->bi_sector >> 3) > 0xffffffffU - xdev->offset)
		goto fail;
	index = (bio->bi_sector >> 3) + xdev->offset;
	bio_for_each_segment(bvec, bio, i) {
		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 0;
fail:
	bio_io_error(bio);
	return 0;
}

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 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;
	int mem_auto_no;
	int i;

	/* Check number of devices. */
	if (devs <= 0 || devs > XPRAM_MAX_DEVS) {
		PRINT_ERR("invalid number %d of devices\n",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[i], 0);
			switch (sizes[i][0]) {
			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++;
	}
	
	PRINT_INFO("  number of devices (partitions): %d \n", xpram_devs);
	for (i = 0; i < xpram_devs; i++) {
		if (xpram_sizes[i])
			PRINT_INFO("  size of partition %d: %u kB\n",
				   i, xpram_sizes[i]);
		else
			PRINT_INFO("  size of partition %d to be set "
				   "automatically\n",i);
	}
	PRINT_DEBUG("  memory needed (for sized partitions): %lu kB\n",
		    mem_needed);
	PRINT_DEBUG("  partitions to be sized automatically: %d\n",
		    mem_auto_no);

	if (mem_needed > pages * 4) {
		PRINT_ERR("Not enough expanded memory available\n");
		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;
		PRINT_INFO("  automatically determined "
			   "partition size: %lu kB\n", mem_auto);
		for (i = 0; i < xpram_devs; i++)
			if (xpram_sizes[i] == 0)
				xpram_sizes[i] = mem_auto;
	}
	return 0;
}

static struct request_queue *xpram_queue;

static int __init xpram_setup_blkdev(void)
{
	unsigned long offset;
	int i, rc = -ENOMEM;

	for (i = 0; i < xpram_devs; i++) {
		struct gendisk *disk = alloc_disk(1);
		if (!disk)
			goto out;
		xpram_disks[i] = disk;
	}

	/*
	 * Register xpram major.
	 */
	rc = register_blkdev(XPRAM_MAJOR, XPRAM_NAME);
	if (rc < 0)
		goto out;

	/*
	 * Assign the other needed values: make request function, sizes and
	 * hardsect size. All the minor devices feature the same value.
	 */
	xpram_queue = blk_alloc_queue(GFP_KERNEL);
	if (!xpram_queue) {
		rc = -ENOMEM;
		goto out_unreg;
	}
	blk_queue_make_request(xpram_queue, xpram_make_request);
	blk_queue_hardsect_size(xpram_queue, 4096);

	/*
	 * 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_queue;
		sprintf(disk->disk_name, "slram%d", i);
		set_capacity(disk, xpram_sizes[i] << 1);
		add_disk(disk);
	}

	return 0;
out_unreg:
	unregister_blkdev(XPRAM_MAJOR, XPRAM_NAME);
out:
	while (i--)
		put_disk(xpram_disks[i]);
	return rc;
}

/*
 * 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]);
		put_disk(xpram_disks[i]);
	}
	unregister_blkdev(XPRAM_MAJOR, XPRAM_NAME);
	blk_cleanup_queue(xpram_queue);
}

static int __init xpram_init(void)
{
	int rc;

	/* Find out size of expanded memory. */
	if (xpram_present() != 0) {
		PRINT_WARN("No expanded memory available\n");
		return -ENODEV;
	}
	xpram_pages = xpram_highest_page_index() + 1;
	PRINT_INFO("  %u pages expanded memory found (%lu KB).\n",
		   xpram_pages, (unsigned long) xpram_pages*4);
	rc = xpram_setup_sizes(xpram_pages);
	if (rc)
		return rc;
	return xpram_setup_blkdev();
}

module_init(xpram_init);
module_exit(xpram_exit);