#pypp 0
// Iris: micro-kernel for a capability-based operating system.
// mips/nand.hhp: NAND driver functions, split off to be used in two places.
// The functions are not inline, so this file must be included exactly once per executable that needs it.
// Copyright 2009 Bas Wijnen <wijnen@debian.org>
//
// 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 3 of the License, 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, see <http://www.gnu.org/licenses/>.

// The following defines are taken from mtd/nand.h in the Linux source.
// Everything not in the nand datasheet is thrown out.

//#define dbgl() debug ("%s:%d\n", __PRETTY_FUNCTION__, __LINE__)
#define dbgl()

// Standard NAND flash commands
#define CMD_READ0		0
#define CMD_READSTART		0x30

#define CMD_READID		0x90

#define CMD_RESET		0xff

#define CMD_SEQIN		0x80
#define CMD_PAGEPROG		0x10

#define CMD_ERASE1		0x60
#define CMD_ERASE2		0xd0

#define CMD_RNDIN		0x85

#define CMD_RNDOUT		5
#define CMD_RNDOUTSTART		0xe0

#define CMD_STATUS		0x70

// Status bits
#define STATUS_FAIL		0x01
#define STATUS_READY		0x40
#define STATUS_WRITABLE		0x80

static volatile char *command
static volatile char *address
static volatile char *data

static unsigned page_bits
static unsigned redundant_bits
static unsigned block_bits
static unsigned size_bits
static unsigned word_size
static unsigned ecc_start

static void unbusy ():
	while !(gpio_get_port (2) & (1 << 30)):
		DELAY ()

static void addr (unsigned d):
	unbusy ()
	*address = d

static void cmd (unsigned d):
	unbusy ()
	*command = d

static void wdata (unsigned d):
	unbusy ()
	*data = d

static unsigned rdata ():
	unbusy ()
	unsigned ret = *data
	return ret

static void reset ():
	// Set up.
	gpio_as_nand ()
	gpio_as_gpio (2, 1 << 30)
	gpio_as_input (2, 1 << 30)
	gpio_enable_pull (2, 1 << 30)
	EMC_NFCSR = EMC_NFCSR_NFE1 | EMC_NFCSR_NFCE1

	// Reset nand.
	cmd (CMD_RESET)

	cmd (CMD_READID)
	addr (0)
	unsigned d = rdata ()
	//unsigned maker = d
	d = rdata ()
	//unsigned device = d
	d = rdata ()
	//unsigned internal_chip_number = 1 << (d & 0x3)
	//unsigned cell_type = 2 << ((d >> 2) & 0x3)
	//unsigned simultaneously_programmed_pages = 1 << ((d >> 4) & 0x3)
	//bool can_interleave_program_between_chips = d & 0x40
	//bool can_cache_program = d & 0x80
	d = rdata ()
	page_bits = 10 + (d & 3)
	debug ("page bits: %d\n", page_bits)
	redundant_bits = (d & 4 ? 4 : 3)
	debug ("redundant bits: %d\n", redundant_bits)
	block_bits = 16 + ((d >> 4) & 3)
	debug ("block bits: %d\n", block_bits)
	word_size = (d & 0x40 ? 16 : 8)
	debug ("word size: %d\n", word_size)
	//unsigned serial_access_minimum = (d & 0x80 ? 25 : 50)
	d = rdata ()
	unsigned num_planes_bits = d >> 2 & 3 
	unsigned plane_bits = 26 + (d >> 4 & 7)
	size_bits = plane_bits + num_planes_bits - 3
	if page_bits == 11:
		ecc_start = 6
	else if page_bits == 12:
		ecc_start = 12
	else:
		debug ("unknown nand type; assuming ecc offset to be 6. This is probably wrong!\n")
		ecc_start = 6

static bool read (unsigned a, char *buffer):
	unsigned column = a & ((1 << page_bits) - 1)
	unsigned row = a >> page_bits
	//debug ("reading %x:", a)
	// Read oob information first.
	char error[12]
	// Spare space (starts at 1 << page_bits)
	//  0: unused
	//  2: detect valid data (at least 1 byte == 0 means valid)
	//  5: unused
	//  6: 9-byte ecc of 1st 512 bytes
	//  15: 9-byte ecc of 2nd 512 bytes
	//  24: 9-byte ecc of 3rd 512 bytes
	//  33: 9-byte ecc of 4th 512 bytes
	//  42: unused
	//  64: end of space

	// For 2 GB nand:
	//  0-11: unused/bad block markers
	// 12-89: 8 times 9-byte ecc
	// 90-127: unused
	// 128: end of space
	unsigned col = (1 << page_bits) + ecc_start + 9 * (column >> 9)
	cmd (CMD_READ0)
	addr (col)
	addr (col >> 8)
	addr (row)
	addr (row >> 8)
	addr (row >> 16)
	cmd (CMD_READSTART)
	//debug ("parity data:")
	bool parity_all_ff = true
	for unsigned t = 0; t < 9; ++t:
		error[t] = rdata ()
		if parity_all_ff && (error[t] & 0xff) != 0xff:
			parity_all_ff = false
		//debug (" %x", error[t] & 0xff)
	//debug ("\n")
	cmd (CMD_RNDOUT)
	addr (column)
	addr (column >> 8)
	cmd (CMD_RNDOUTSTART)
	EMC_NFINTS = 0
	EMC_NFECR = EMC_NFECR_ECCE | EMC_NFECR_RS | EMC_NFECR_RS_DECODING | EMC_NFECR_ERST
	bool all_ff = true
	for unsigned t = 0; t < 0x200; ++t:
		buffer[t] = rdata ()
		if all_ff && (buffer[t] & 0xff) != 0xff:
			all_ff = false
	if !all_ff || !parity_all_ff:
		for unsigned t = 0; t < 9; ++t:
			((volatile char *)&EMC_NFPAR (0))[t] = error[t]
		EMC_NFECR = EMC_NFECR_ECCE | EMC_NFECR_RS | EMC_NFECR_RS_DECODING | EMC_NFECR_PRDY
		while !(EMC_NFINTS & EMC_NFINTS_DECF):
			DELAY ()
		unsigned ints = EMC_NFINTS
		if ints & EMC_NFINTS_UNCOR:
			debug ("uncorrectable error in nand at %x\n", a)
			return false
		unsigned errs = (ints & EMC_NFINTS_ERRCNT_MASK) >> EMC_NFINTS_ERRCNT_BIT
		for unsigned i = 0; i < errs; ++i:
			unsigned err = EMC_NFERR (i)
			unsigned index = (err >> 16) - 1
			unsigned mask = err & 0x1ff
			unsigned bit = index * 9
			unsigned offset= bit & 7
			unsigned byte = bit / 8
			debug ("correcting %x on %x+%d\n", mask, byte, offset)
			unsigned data = buffer[byte] | buffer[byte + 1] << 8
			data ^= mask << offset
			buffer[byte] = data
			buffer[byte + 1] = data >> 8
	#if 0
	for unsigned i = 0; i < 0x10; ++i:
		if (buffer[i] & 0xff) < 0x10:
			debug (" 0")
		else:
			debug (" ")
		debug ("%x", buffer[i] & 0xff)
	debug ("\n")
	#endif
	return true

static void write (unsigned a, char *buffer):
	unsigned row = a >> page_bits
	//debug ("writing: %x/%x\n", a, row)
	cmd (CMD_SEQIN)
	addr (0)
	addr (0)
	addr (row)
	addr (row >> 8)
	addr (row >> 16)
	char ecc[8][12]
	for unsigned i = 0; i < 1 << (page_bits - 9); ++i:
		bool all_ff = true
		EMC_NFECR = EMC_NFECR_ECCE | EMC_NFECR_RS | EMC_NFECR_RS_ENCODING | EMC_NFECR_ERST
		//debug ("writing data from %x\n", (unsigned)buffer + i * 0x200)
		for unsigned j = 0; j < 0x200; ++j:
			wdata (buffer[i * 0x200 + j])
			if all_ff && (buffer[i * 0x200 + j] & 0xff) != 0xff:
				all_ff = false
		if !all_ff:
			while !(EMC_NFINTS & EMC_NFINTS_ENCF):
				DELAY ()
			for unsigned t = 0; t < 9; ++t:
				ecc[i][t] = ((volatile char *)&EMC_NFPAR (0))[t]
			//debug ("parity for %x:", i * 0x200 + a)
			//for unsigned t = 0; t < 9; ++t:
				//debug (" %x", ecc[i][t] & 0xff)
			//kdebug ("\n")
		else:
			for unsigned t = 0; t < 9; ++t:
				ecc[i][t] = 0xff
	// Spare space (starts at 1 << page_bits)
	//  0: unused
	//  2: detect valid data (at least 1 byte == 0 means valid)
	//  5: unused
	//  6: 9-byte ecc of 1st 512 bytes
	//  15: 9-byte ecc of 2nd 512 bytes
	//  24: 9-byte ecc of 3rd 512 bytes
	//  33: 9-byte ecc of 4th 512 bytes
	//  42: unused
	//  64: end of space

	// For 2 GB nand:
	//  0-11: unused/bad block markers
	// 12-89: 8 times 9-byte ecc
	// 90-127: unused
	// 128: end of space
	for unsigned i = 0; i < ecc_start; ++i:
		wdata (i == 4 ? 0 : 0xff)
	for unsigned i = 0; i < 1 << (page_bits - 9); ++i:
		for unsigned j = 0; j < 9; ++j:
			wdata (ecc[i][j])
	cmd (CMD_PAGEPROG)
	// Wait at least 100 ns.
	DELAY ()
	cmd (CMD_READ0)
	addr (0)
	addr (0)
	addr (row)
	addr (row >> 8)
	addr (row >> 16)
	cmd (CMD_READSTART)
	for unsigned i = 0; i < 1 << (page_bits - 9); ++i:
		EMC_NFINTS = 0
		EMC_NFECR = EMC_NFECR_ECCE | EMC_NFECR_RS | EMC_NFECR_RS_DECODING | EMC_NFECR_ERST
		for unsigned t = 0; t < 0x200; ++t:
			unsigned r = rdata () & 0xff
			if r != (buffer[i * 0x200 + t] & 0xff):
				debug ("program error at %x: %x != %x\n", i * 0x200 + t, buffer[i * 0x200 + t] & 0xff, r)
		for unsigned t = 0; t < 9; ++t:
			((volatile char *)&EMC_NFPAR (0))[t] = ecc[i][t]
		EMC_NFECR = EMC_NFECR_ECCE | EMC_NFECR_RS | EMC_NFECR_RS_DECODING | EMC_NFECR_PRDY
		while !(EMC_NFINTS & EMC_NFINTS_DECF):
			DELAY ()
		unsigned ints = EMC_NFINTS
		if ints & EMC_NFINTS_UNCOR:
			debug ("uncorrectable error during verify\n")
			continue
		unsigned errs = (ints & EMC_NFINTS_ERRCNT_MASK) >> EMC_NFINTS_ERRCNT_BIT
		for unsigned i = 0; i < errs; ++i:
			unsigned err = EMC_NFERR (i)
			unsigned index = (err >> 16) - 1
			unsigned mask = err & 0x1ff
			unsigned bit = index * 9
			unsigned offset= bit & 7
			unsigned byte = bit / 8
			debug ("error detected by parity: %x on %x+%d\n", mask, byte, offset)
	for unsigned i = 0; i < ecc_start; ++i:
		if rdata () != (i == 4 ? 0 : 0xff):
			debug ("incorrect extra data at byte %d\n", i)
	for unsigned i = 0; i < 1 << (page_bits - 9); ++i:
		for unsigned j = 0; j < 9; ++j:
			unsigned r = rdata () & 0xff
			if r != (ecc[i][j] & 0xff):
				debug ("ecc doesn't match: %x != %x\n", r, ecc[i][j] & 0xff)
	//debug ("nand program %x:", a)
	#if 0
	for unsigned i = 0; i < 0x10; ++i:
		if (buffer[i] & 0xff) < 0x10:
			debug (" 0")
		else:
			debug (" ")
		debug ("%x", buffer[i] & 0xff)
	debug ("\n")
	#endif

static void erase (unsigned a):
	unsigned row = a >> page_bits
	cmd (CMD_ERASE1)
	addr (row)
	addr (row >> 8)
	addr (row >> 16)
	cmd (CMD_ERASE2)
	//debug ("nand erase %d done\n", a)