[ NOTE: The virt_to_bus() and bus_to_virt() functions have been superseded by the functionality provided by the PCI DMA interface (see Documentation/DMA-mapping.txt). They continue to be documented below for historical purposes, but new code must not use them. --davidm 00/12/12 ] [ This is a mail message in response to a query on IO mapping, thus the strange format for a "document" ] The AHA-1542 is a bus-master device, and your patch makes the driver give the controller the physical address of the buffers, which is correct on x86 (because all bus master devices see the physical memory mappings directly). However, on many setups, there are actually _three_ different ways of looking at memory addresses, and in this case we actually want the third, the so-called "bus address". Essentially, the three ways of addressing memory are (this is "real memory", that is, normal RAM--see later about other details): - CPU untranslated. This is the "physical" address. Physical address 0 is what the CPU sees when it drives zeroes on the memory bus. - CPU translated address. This is the "virtual" address, and is completely internal to the CPU itself with the CPU doing the appropriate translations into "CPU untranslated". - bus address. This is the address of memory as seen by OTHER devices, not the CPU. Now, in theory there could be many different bus addresses, with each device seeing memory in some device-specific way, but happily most hardware designers aren't actually actively trying to make things any more complex than necessary, so you can assume that all external hardware sees the memory the same way. Now, on normal PCs the bus address is exactly the same as the physical address, and things are very simple indeed. However, they are that simple because the memory and the devices share the same address space, and that is not generally necessarily true on other PCI/ISA setups. Now, just as an example, on the PReP (PowerPC Reference Platform), the CPU sees a memory map something like this (this is from memory): 0-2 GB "real memory" 2 GB-3 GB "system IO" (inb/out and similar accesses on x86) 3 GB-4 GB "IO memory" (shared memory over the IO bus) Now, that looks simple enough. However, when you look at the same thing from the viewpoint of the devices, you have the reverse, and the physical memory address 0 actually shows up as address 2 GB for any IO master. So when the CPU wants any bus master to write to physical memory 0, it has to give the master address 0x80000000 as the memory address. So, for example, depending on how the kernel is actually mapped on the PPC, you can end up with a setup like this: physical address: 0 virtual address: 0xC0000000 bus address: 0x80000000 where all the addresses actually point to the same thing. It's just seen through different translations.. Similarly, on the Alpha, the normal translation is physical address: 0 virtual address: 0xfffffc0000000000 bus address: 0x40000000 (but there are also Alphas where the physical address and the bus address are the same). Anyway, the way to look up all these translations, you do #include phys_addr = virt_to_phys(virt_addr); virt_addr = phys_to_virt(phys_addr); bus_addr = virt_to_bus(virt_addr); virt_addr = bus_to_virt(bus_addr); Now, when do you need these? You want the _virtual_ address when you are actually going to access that pointer from the kernel. So you can have something like this: /* * this is the hardware "mailbox" we use to communicate with * the controller. The controller sees this directly. */ struct mailbox { __u32 status; __u32 bufstart; __u32 buflen; .. } mbox; unsigned char * retbuffer; /* get the address from the controller */ retbuffer = bus_to_virt(mbox.bufstart); switch (retbuffer[0]) { case STATUS_OK: ... on the other hand, you want the bus address when you have a buffer that you want to give to the controller: /* ask the controller to read the sense status into "sense_buffer" */ mbox.bufstart = virt_to_bus(&sense_buffer); mbox.buflen = sizeof(sense_buffer); mbox.status = 0; notify_controller(&mbox); And you generally _never_ want to use the physical address, because you can't use that from the CPU (the CPU only uses translated virtual addresses), and you can't use it from the bus master. So why do we care about the physical address at all? We do need the physical address in some cases, it's just not very often in normal code. The physical address is needed if you use memory mappings, for example, because the "remap_pfn_range()" mm function wants the physical address of the memory to be remapped as measured in units of pages, a.k.a. the pfn (the memory management layer doesn't know about devices outside the CPU, so it shouldn't need to know about "bus addresses" etc). NOTE NOTE NOTE! The above is only one part of the whole equation. The above only talks about "real memory", that is, CPU memory (RAM). There is a completely different type of memory too, and that's the "shared memory" on the PCI or ISA bus. That's generally not RAM (although in the case of a video graphics card it can be normal DRAM that is just used for a frame buffer), but can be things like a packet buffer in a network card etc. This memory is called "PCI memory" or "shared memory" or "IO memory" or whatever, and there is only one way to access it: the readb/writeb and related functions. You should never take the address of such memory, because there is really nothing you can do with such an address: it's not conceptually in the same memory space as "real memory" at all, so you cannot just dereference a pointer. (Sadly, on x86 it _is_ in the same memory space, so on x86 it actually works to just deference a pointer, but it's not portable). For such memory, you can do things like - reading: /* * read first 32 bits from ISA memory at 0xC0000, aka * C000:0000 in DOS terms */ unsigned int signature = isa_readl(0xC0000); - remapping and writing: /* * remap framebuffer PCI memory area at 0xFC000000, * size 1MB, so that we can access it: We can directly * access only the 640k-1MB area, so anything else * has to be remapped. */ char * baseptr = ioremap(0xFC000000, 1024*1024); /* write a 'A' to the offset 10 of the area */ writeb('A',baseptr+10); /* unmap when we unload the driver */ iounmap(baseptr); - copying and clearing: /* get the 6-byte Ethernet address at ISA address E000:0040 */ memcpy_fromio(kernel_buffer, 0xE0040, 6); /* write a packet to the driver */ memcpy_toio(0xE1000, skb->data, skb->len); /* clear the frame buffer */ memset_io(0xA0000, 0, 0x10000); OK, that just about covers the basics of accessing IO portably. Questions? Comments? You may think that all the above is overly complex, but one day you might find yourself with a 500 MHz Alpha in front of you, and then you'll be happy that your driver works ;) Note that kernel versions 2.0.x (and earlier) mistakenly called the ioremap() function "vremap()". ioremap() is the proper name, but I didn't think straight when I wrote it originally. People who have to support both can do something like: /* support old naming silliness */ #if LINUX_VERSION_CODE < 0x020100 #define ioremap vremap #define iounmap vfree #endif at the top of their source files, and then they can use the right names even on 2.0.x systems. And the above sounds worse than it really is. Most real drivers really don't do all that complex things (or rather: the complexity is not so much in the actual IO accesses as in error handling and timeouts etc). It's generally not hard to fix drivers, and in many cases the code actually looks better afterwards: unsigned long signature = *(unsigned int *) 0xC0000; vs unsigned long signature = readl(0xC0000); I think the second version actually is more readable, no? Linus ='#n151'>151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 
// SPDX-License-Identifier: GPL-2.0+
/*
 * (C) Copyright 2000-2009
 * Wolfgang Denk, DENX Software Engineering, wd@denx.de.
 */

/*
 * Boot support
 */
#include <common.h>
#include <bootm.h>
#include <command.h>
#include <env.h>
#include <errno.h>
#include <image.h>
#include <malloc.h>
#include <nand.h>
#include <asm/byteorder.h>
#include <asm/global_data.h>
#include <linux/ctype.h>
#include <linux/err.h>
#include <u-boot/zlib.h>
#include <mapmem.h>

DECLARE_GLOBAL_DATA_PTR;

#if defined(CONFIG_CMD_IMI)
static int image_info(unsigned long addr);
#endif

#if defined(CONFIG_CMD_IMLS)
#include <flash.h>
#include <mtd/cfi_flash.h>
extern flash_info_t flash_info[]; /* info for FLASH chips */
#endif

#if defined(CONFIG_CMD_IMLS) || defined(CONFIG_CMD_IMLS_NAND)
static int do_imls(struct cmd_tbl *cmdtp, int flag, int argc,
		   char *const argv[]);
#endif

/* we overload the cmd field with our state machine info instead of a
 * function pointer */
static struct cmd_tbl cmd_bootm_sub[] = {
	U_BOOT_CMD_MKENT(start, 0, 1, (void *)BOOTM_STATE_START, "", ""),
	U_BOOT_CMD_MKENT(loados, 0, 1, (void *)BOOTM_STATE_LOADOS, "", ""),
#ifdef CONFIG_SYS_BOOT_RAMDISK_HIGH
	U_BOOT_CMD_MKENT(ramdisk, 0, 1, (void *)BOOTM_STATE_RAMDISK, "", ""),
#endif
#ifdef CONFIG_OF_LIBFDT
	U_BOOT_CMD_MKENT(fdt, 0, 1, (void *)BOOTM_STATE_FDT, "", ""),
#endif
	U_BOOT_CMD_MKENT(cmdline, 0, 1, (void *)BOOTM_STATE_OS_CMDLINE, "", ""),
	U_BOOT_CMD_MKENT(bdt, 0, 1, (void *)BOOTM_STATE_OS_BD_T, "", ""),
	U_BOOT_CMD_MKENT(prep, 0, 1, (void *)BOOTM_STATE_OS_PREP, "", ""),
	U_BOOT_CMD_MKENT(fake, 0, 1, (void *)BOOTM_STATE_OS_FAKE_GO, "", ""),
	U_BOOT_CMD_MKENT(go, 0, 1, (void *)BOOTM_STATE_OS_GO, "", ""),
};

static int do_bootm_subcommand(struct cmd_tbl *cmdtp, int flag, int argc,
			       char *const argv[])
{
	int ret = 0;
	long state;
	struct cmd_tbl *c;

	c = find_cmd_tbl(argv[0], &cmd_bootm_sub[0], ARRAY_SIZE(cmd_bootm_sub));
	argc--; argv++;

	if (c) {
		state = (long)c->cmd;
		if (state == BOOTM_STATE_START)
			state |= BOOTM_STATE_FINDOS | BOOTM_STATE_FINDOTHER;
	} else {
		/* Unrecognized command */
		return CMD_RET_USAGE;
	}

	if (((state & BOOTM_STATE_START) != BOOTM_STATE_START) &&
	    images.state >= state) {
		printf("Trying to execute a command out of order\n");
		return CMD_RET_USAGE;
	}

	ret = do_bootm_states(cmdtp, flag, argc, argv, state, &images, 0);

	return ret;
}

/*******************************************************************/
/* bootm - boot application image from image in memory */
/*******************************************************************/

int do_bootm(struct cmd_tbl *cmdtp, int flag, int argc, char *const argv[])
{
#ifdef CONFIG_NEEDS_MANUAL_RELOC
	static int relocated = 0;

	if (!relocated) {
		int i;

		/* relocate names of sub-command table */