devflash.c

这是一个同样来自贝尔实验室的和UNIX有着渊源的操作系统, 其简洁的设计和实现易于我们学习和理解

	FlashRegion *r;
	Flash *flash;

	flash = findflash(addr);
	if (flash == nil)
		error(Ebadarg);
	if(flash->bootprotect == 0)
		return;
	if(flash->nr == 0)
		error("writing over boot loader disallowed");
	r = flash->r;
	if(addr >= r->addr && addr < r->addr + r->size)
		error("writing over boot loader disallowed");
}

static ulong
blockstart(Flash *flash, ulong addr)
{
	FlashRegion *r, *e;
	ulong x;

	r = flash->r;
	for(e = &flash->r[flash->nr]; r < e; r++){
		if(addr >= r->addr && addr < r->end){
			x = addr - r->addr;
			x /= r->size;
			return r->addr + x*r->size;
		}
	}
			
	return (ulong)-1;
}

static ulong
blockend(Flash *flash, ulong addr)
{
	FlashRegion *r, *e;
	ulong x;

	r = flash->r;
	for(e = &flash->r[flash->nr]; r < e; r++)
		if(addr >= r->addr && addr < r->end){
			x = addr - r->addr;
			x /= r->size;
			return r->addr + (x+1)*r->size;
		}
			
	return (ulong)-1;
}

static long
flashctlwrite(FPart *fp, char *p, long n)
{
	Cmdbuf *cmd;
	ulong off;
	Flash *flash;

	if(fp == nil)
		panic("flashctlwrite");

	flash = fp->flash;
	cmd = parsecmd(p, n);
	wlock(flash);
	if(waserror()){
		wunlock(flash);
		nexterror();
	}
	if(strcmp(cmd->f[0], "erase") == 0){
		switch(cmd->nf){
		case 2:
			/* erase a single block in the partition */
			off = atoi(cmd->f[1]);
			off += fp->start;
			if(off >= fp->end)
				error("region not in partition");
			if(off != blockstart(flash, off))
				error("erase must be a block boundary");
			bootprotect(off);
			(*flash->alg->erase)(flash, off);
			break;
		case 1:
			/* erase the whole partition */
			bootprotect(fp->start);
			for(off = fp->start; off < fp->end; off = blockend(flash, off))
				(*flash->alg->erase)(flash, off);
			break;
		default:
			error(Ebadarg);
		}
	} else if(strcmp(cmd->f[0], "add") == 0){
		if(cmd->nf != 4)
			error(Ebadarg);
		addpart(fp, cmd->f[1], strtoul(cmd->f[2], nil, 0), strtoul(cmd->f[3], nil, 0));
	} else if(strcmp(cmd->f[0], "remove") == 0){
		rempart(fp);
	} else if(strcmp(cmd->f[0], "protectboot") == 0){
		if(cmd->nf == 0 || strcmp(cmd->f[1], "off") != 0)
			flash->bootprotect = 1;
		else
			flash->bootprotect = 0;
	} else
		error(Ebadarg);
	poperror();
	wunlock(flash);
	free(cmd);

	return n;
}

static long
flashdatawrite(FPart *fp, uchar *p, long n, long off)
{
	uchar *end;
	int m;
	int on;
	long ooff;
	uchar *buf;
	Flash *flash;

	if(fp == nil)
		panic("flashdatawrite");

	flash = fp->flash;
	buf = nil;
	wlock(flash);
	if(waserror()){
		wunlock(flash);
		if(buf != nil)
			free(buf);
		nexterror();
	}

	if(fp->name == nil)
		error("partition vanished");
	if(!iseve())
		error(Eperm);

	/* can't cross partition boundaries */
	off += fp->start;
	if(off >= fp->end || off+n > fp->end || n <= 0)
		error(Ebadarg);

	/* make sure we're not writing the boot sector */
	bootprotect(off);

	on = n;

	/*
	 *  get the data into kernel memory to avoid faults during writing.
	 *  if write is not on a quad boundary or not a multiple of 4 bytes,
	 *  extend with data already in flash.
	 */
	buf = smalloc(n+8);
	m = off & 3;
	if(m){
		*(ulong*)buf = flash->p[off>>Wshift];
		n += m;
		off -= m;
	}
	if(n & 3){
		n -= n & 3;
		*(ulong*)(&buf[n]) = flash->p[(off+n)>>Wshift];
		n += 4;
	}
	memmove(&buf[m], p, on);

	/* (*flash->alg->write) can't cross blocks */
	ooff = off;
	p = buf;
	for(end = p + n; p < end; p += m){
		m = blockend(flash, off) - off;
		if(m > end - p)
			m = end - p;
		if(m > Maxwchunk)
			m = Maxwchunk;
		(*flash->alg->write)(flash, p, m, off);
		off += m;
	}

	/* make sure write succeeded */
	if(memcmp(buf, &flash->p[ooff>>Wshift], n) != 0)
		error("written bytes don't match");

	wunlock(flash);
	free(buf);
	poperror();

	return on;
}

static long	 
flashwrite(Chan* c, void* a, long n, vlong off)
{
	int t;

	if(c->qid.type == QTDIR)
		error(Eperm);

	if(!iseve())
		error(Eperm);

	t = FTYPE(c->qid.path);
	switch(t){
	default:
		panic("flashwrite");
	case Qfctl:
		n = flashctlwrite(FPART(c->qid.path), a, n);
		break;
	case Qfdata:
		n = flashdatawrite(FPART(c->qid.path), a, n, off);
		break;
	}
	return n;
}

Dev flashdevtab = {
	'F',
	"flash",

	devreset,
	flashinit,
	devshutdown,
	flashattach,
	flashwalk,
	flashstat,
	flashopen,
	devcreate,
	flashclose,
	flashread,
	devbread,
	flashwrite,
	devbwrite,
	devremove,
	devwstat,
};

enum
{
	/* status register */
	ISEs_lockerr=		1<<1,
	ISEs_powererr=		1<<3,
	ISEs_progerr=		1<<4,
	ISEs_eraseerr=		1<<5,
	ISEs_ready=		1<<7,
	ISEs_err= (ISEs_lockerr|ISEs_powererr|ISEs_progerr|ISEs_eraseerr),

	/* extended status register */
	ISExs_bufavail=		1<<7,
};

/* intel/sharp extended command set */
static void
ise_reset(Flash* flash)
{
	flash->p[reg(0xaa)] = mirror(0xff);	/* reset */
}

static void
ise_id(Flash* flash)
{
	ise_reset(flash);
	flash->p[reg(0xaaa)] = mirror(0x90);	/* uncover vendor info */
	flash->manid = fromendian(flash->p[reg(0x0)]);
	flash->devid = fromendian(flash->p[reg(0x1)]);
	ise_reset(flash);
}

static void
ise_clearerror(Flash* flash)
{
	flash->p[reg(0x200)] = mirror(0x50);

}

static void
ise_error(int bank, ulong status)
{
	char err[64];

	if(status & (ISEs_lockerr)){
		sprint(err, "flash%d: block locked %lux", bank, status);
		error(err);
	}
	if(status & (ISEs_powererr)){
		sprint(err, "flash%d: low prog voltage %lux", bank, status);
		error(err);
	}
	if(status & (ISEs_progerr|ISEs_eraseerr)){
		sprint(err, "flash%d: i/o error %lux", bank, status);
		error(err);
	}
}
static void
ise_erase(Flash *flash, ulong addr)
{
	ulong start;
	ulong x;

	addr >>= Wshift;

	flashprogpower(1);
	flash->p[addr] = mirror(0x20);
	flash->p[addr] = mirror(0xd0);
	start = m->ticks;
	do {
		x = fromendian(flash->p[addr]);
		if((x & mirror(ISEs_ready)) == mirror(ISEs_ready))
			break;
	} while(TK2MS(m->ticks-start) < 1500);
	flashprogpower(0);

	ise_clearerror(flash);
	ise_error(0, x);
	ise_error(1, x>>16);

	ise_reset(flash);
}
/*
 *  the flash spec claimes writing goes faster if we use
 *  the write buffer.  We fill the write buffer and then
 *  issue the write request.  After the write request,
 *  subsequent reads will yield the status register.
 *
 *  returns the status, even on timeouts.
 *
 *  NOTE: I tried starting back to back buffered writes
 *	without reading the status in between, as the
 *	flowchart in the intel data sheet suggests.
 *	However, it always responded with an illegal
 *	command sequence, so I must be missing something.
 *	If someone learns better, please email me, though
 *	I doubt it will be much faster. -  [e-mail]
 */
static long
ise_wbwrite(Flash *flash, Fword *p, int n, ulong off, ulong baddr, ulong *status)
{
	Fword x;
	ulong start;
	int i;
	int s;

	/* put flash into write buffer mode */
	start = m->ticks;
	for(;;) {
		s = splhi();
		/* request write buffer mode */
		flash->p[baddr] = mirror(0xe8);

		/* look at extended status reg for status */
		if((flash->p[baddr] & mirror(1<<7)) == mirror(1<<7))
			break;
		splx(s);

		/* didn't work, keep trying for 2 secs */
		if(TK2MS(m->ticks-start) > 2000){
			/* set up to read status */
			flash->p[baddr] = mirror(0x70);
			*status = fromendian(flash->p[baddr]);
			pprint("write buffered cmd timed out\n");
			return -1;
		}
	}

	/* fill write buffer */
	flash->p[baddr] = mirror(n-1);
	for(i = 0; i < n; i++)
		flash->p[off+i] = *p++;

	/* program from buffer */
	flash->p[baddr] = mirror(0xd0);
	splx(s);

	/* wait till the programming is done */
	start = m->ticks;
	for(;;) {
		x = flash->p[baddr];	/* read status register */
		*status = fromendian(x);
		if((x & mirror(ISEs_ready)) == mirror(ISEs_ready))
			break;
		if(TK2MS(m->ticks-start) > 2000){
			pprint("read status timed out\n");
			return -1;
		}
	}
	if(x & mirror(ISEs_err))
		return -1;

	return n;
}

static void
ise_write(Flash *flash, void *a, long n, ulong off)
{
	Fword *p, *end;
	int i, wbsize;
	ulong x, baddr;

 	/* everything in terms of Fwords */
	wbsize = flash->wbsize >> Wshift;
	baddr = blockstart(flash, off) >> Wshift;
	off >>= Wshift;
	n >>= Wshift;
	p = a;

	/* first see if write will succeed */
	for(i = 0; i < n; i++)
		if((p[i] & flash->p[off+i]) != p[i])
			error("flash needs erase");

	if(waserror()){
		ise_reset(flash);
		flashprogpower(0);
		nexterror();
	}
	flashprogpower(1);

	/*
	 *  use the first write to reach
 	 *  a write buffer boundary.  the intel maunal
	 *  says writes starting at wb boundaries
	 *  maximize speed.
	 */
	i = wbsize - (off & (wbsize-1));
	for(end = p + n; p < end;){
		if(i > end - p)
			i = end - p;

		if(ise_wbwrite(flash, p, i, off, baddr, &x) < 0)
			break;

		off += i;
		p += i;
		i = wbsize;
	}

	ise_clearerror(flash);
	ise_error(0, x);
	ise_error(1, x>>16);

	ise_reset(flash);
	flashprogpower(0);
	poperror();
}

/* amd/fujitsu standard command set
 *	I don't have an amd chipset to work with
 *	so I'm loathe to write this yet.  If someone
 *	else does, please send it to me and I'll
 *	incorporate it -- [e-mail]
 */
static void
afs_reset(Flash *flash)
{
	flash->p[reg(0xaa)] = mirror(0xf0);	/* reset */
}
static void
afs_id(Flash *flash)
{
	afs_reset(flash);
	flash->p[reg(0xaa)] = mirror(0xf0);	/* reset */
	flash->p[reg(0xaaa)] = mirror(0xaa);	/* query vendor block */
	flash->p[reg(0x554)] = mirror(0x55);
	flash->p[reg(0xaaa)] = mirror(0x90);
	flash->manid = fromendian(flash->p[reg(0x00)]);
	afs_reset(flash);
	flash->p[reg(0xaaa)] = mirror(0xaa);	/* query vendor block */
	flash->p[reg(0x554)] = mirror(0x55);
	flash->p[reg(0xaaa)] = mirror(0x90);
	flash->devid = fromendian(flash->p[reg(0x02)]);
	afs_reset(flash);
}
static void
afs_erase(Flash*, ulong)
{
	error("amd/fujistsu erase not implemented");
}
static void
afs_write(Flash*, void*, long, ulong)
{
	error("amd/fujistsu write not implemented");
}