rtc_from4.c

基于linux-2.6.28的mtd驱动

 */
static void rtc_from4_calculate_ecc(struct mtd_info *mtd, const u_char *dat, u_char *ecc_code)
{
	volatile unsigned short *rs_eccn = (volatile unsigned short *)(rtc_from4_fio_base + RTC_FROM4_RS_ECCN);
	unsigned short value;
	int i;

	for (i = 0; i < 8; i++) {
		value = *rs_eccn;
		ecc_code[i] = (unsigned char)value;
		rs_eccn++;
	}
	ecc_code[7] |= 0x0f;	/* set the last four bits (not used) */
}

/*
 * rtc_from4_correct_data - hardware specific code to correct data using ECC code
 * @mtd:	MTD device structure
 * @buf:	buffer containing the data to generate ECC codes
 * @ecc1	ECC codes read
 * @ecc2	ECC codes calculated
 *
 * The FPGA tells us fast, if there's an error or not. If no, we go back happy
 * else we read the ecc results from the fpga and call the rs library to decode
 * and hopefully correct the error.
 *
 */
static int rtc_from4_correct_data(struct mtd_info *mtd, const u_char *buf, u_char *ecc1, u_char *ecc2)
{
	int i, j, res;
	unsigned short status;
	uint16_t par[6], syn[6];
	uint8_t ecc[8];
	volatile unsigned short *rs_ecc;

	status = *((volatile unsigned short *)(rtc_from4_fio_base + RTC_FROM4_RS_ECC_CHK));

	if (!(status & RTC_FROM4_RS_ECC_CHK_ERROR)) {
		return 0;
	}

	/* Read the syndrom pattern from the FPGA and correct the bitorder */
	rs_ecc = (volatile unsigned short *)(rtc_from4_fio_base + RTC_FROM4_RS_ECC);
	for (i = 0; i < 8; i++) {
		ecc[i] = bitrev8(*rs_ecc);
		rs_ecc++;
	}

	/* convert into 6 10bit syndrome fields */
	par[5] = rs_decoder->index_of[(((uint16_t) ecc[0] >> 0) & 0x0ff) | (((uint16_t) ecc[1] << 8) & 0x300)];
	par[4] = rs_decoder->index_of[(((uint16_t) ecc[1] >> 2) & 0x03f) | (((uint16_t) ecc[2] << 6) & 0x3c0)];
	par[3] = rs_decoder->index_of[(((uint16_t) ecc[2] >> 4) & 0x00f) | (((uint16_t) ecc[3] << 4) & 0x3f0)];
	par[2] = rs_decoder->index_of[(((uint16_t) ecc[3] >> 6) & 0x003) | (((uint16_t) ecc[4] << 2) & 0x3fc)];
	par[1] = rs_decoder->index_of[(((uint16_t) ecc[5] >> 0) & 0x0ff) | (((uint16_t) ecc[6] << 8) & 0x300)];
	par[0] = (((uint16_t) ecc[6] >> 2) & 0x03f) | (((uint16_t) ecc[7] << 6) & 0x3c0);

	/* Convert to computable syndrome */
	for (i = 0; i < 6; i++) {
		syn[i] = par[0];
		for (j = 1; j < 6; j++)
			if (par[j] != rs_decoder->nn)
				syn[i] ^= rs_decoder->alpha_to[rs_modnn(rs_decoder, par[j] + i * j)];

		/* Convert to index form */
		syn[i] = rs_decoder->index_of[syn[i]];
	}

	/* Let the library code do its magic. */
	res = decode_rs8(rs_decoder, (uint8_t *) buf, par, 512, syn, 0, NULL, 0xff, NULL);
	if (res > 0) {
		DEBUG(MTD_DEBUG_LEVEL0, "rtc_from4_correct_data: " "ECC corrected %d errors on read\n", res);
	}
	return res;
}

/**
 * rtc_from4_errstat - perform additional error status checks
 * @mtd:	MTD device structure
 * @this:	NAND chip structure
 * @state:	state or the operation
 * @status:	status code returned from read status
 * @page:	startpage inside the chip, must be called with (page & this->pagemask)
 *
 * Perform additional error status checks on erase and write failures
 * to determine if errors are correctable.  For this device, correctable
 * 1-bit errors on erase and write are considered acceptable.
 *
 * note: see pages 34..37 of data sheet for details.
 *
 */
static int rtc_from4_errstat(struct mtd_info *mtd, struct nand_chip *this,
			     int state, int status, int page)
{
	int er_stat = 0;
	int rtn, retlen;
	size_t len;
	uint8_t *buf;
	int i;

	this->cmdfunc(mtd, NAND_CMD_STATUS_CLEAR, -1, -1);

	if (state == FL_ERASING) {

		for (i = 0; i < 4; i++) {
			if (!(status & 1 << (i + 1)))
				continue;
			this->cmdfunc(mtd, (NAND_CMD_STATUS_ERROR + i + 1),
				      -1, -1);
			rtn = this->read_byte(mtd);
			this->cmdfunc(mtd, NAND_CMD_STATUS_RESET, -1, -1);

			/* err_ecc_not_avail */
			if (!(rtn & ERR_STAT_ECC_AVAILABLE))
				er_stat |= 1 << (i + 1);
		}

	} else if (state == FL_WRITING) {

		unsigned long corrected = mtd->ecc_stats.corrected;

		/* single bank write logic */
		this->cmdfunc(mtd, NAND_CMD_STATUS_ERROR, -1, -1);
		rtn = this->read_byte(mtd);
		this->cmdfunc(mtd, NAND_CMD_STATUS_RESET, -1, -1);

		if (!(rtn & ERR_STAT_ECC_AVAILABLE)) {
			/* err_ecc_not_avail */
			er_stat |= 1 << 1;
			goto out;
		}

		len = mtd->writesize;
		buf = kmalloc(len, GFP_KERNEL);
		if (!buf) {
			printk(KERN_ERR "rtc_from4_errstat: Out of memory!\n");
			er_stat = 1;
			goto out;
		}

		/* recovery read */
		rtn = nand_do_read(mtd, page, len, &retlen, buf);

		/* if read failed or > 1-bit error corrected */
		if (rtn || (mtd->ecc_stats.corrected - corrected) > 1)
			er_stat |= 1 << 1;
		kfree(buf);
	}
out:
	rtn = status;
	if (er_stat == 0) {	/* if ECC is available   */
		rtn = (status & ~NAND_STATUS_FAIL);	/*   clear the error bit */
	}

	return rtn;
}
#endif

/*
 * Main initialization routine
 */
static int __init rtc_from4_init(void)
{
	struct nand_chip *this;
	unsigned short bcr1, bcr2, wcr2;
	int i;
	int ret;

	/* Allocate memory for MTD device structure and private data */
	rtc_from4_mtd = kmalloc(sizeof(struct mtd_info) + sizeof(struct nand_chip), GFP_KERNEL);
	if (!rtc_from4_mtd) {
		printk("Unable to allocate Renesas NAND MTD device structure.\n");
		return -ENOMEM;
	}

	/* Get pointer to private data */
	this = (struct nand_chip *)(&rtc_from4_mtd[1]);

	/* Initialize structures */
	memset(rtc_from4_mtd, 0, sizeof(struct mtd_info));
	memset(this, 0, sizeof(struct nand_chip));

	/* Link the private data with the MTD structure */
	rtc_from4_mtd->priv = this;
	rtc_from4_mtd->owner = THIS_MODULE;

	/* set area 5 as PCMCIA mode to clear the spec of tDH(Data hold time;9ns min) */
	bcr1 = *SH77X9_BCR1 & ~0x0002;
	bcr1 |= 0x0002;
	*SH77X9_BCR1 = bcr1;

	/* set */
	bcr2 = *SH77X9_BCR2 & ~0x0c00;
	bcr2 |= 0x0800;
	*SH77X9_BCR2 = bcr2;

	/* set area 5 wait states */
	wcr2 = *SH77X9_WCR2 & ~0x1c00;
	wcr2 |= 0x1c00;
	*SH77X9_WCR2 = wcr2;

	/* Set address of NAND IO lines */
	this->IO_ADDR_R = rtc_from4_fio_base;
	this->IO_ADDR_W = rtc_from4_fio_base;
	/* Set address of hardware control function */
	this->cmd_ctrl = rtc_from4_hwcontrol;
	/* Set address of chip select function */
	this->select_chip = rtc_from4_nand_select_chip;
	/* command delay time (in us) */
	this->chip_delay = 100;
	/* return the status of the Ready/Busy line */
	this->dev_ready = rtc_from4_nand_device_ready;

#ifdef RTC_FROM4_HWECC
	printk(KERN_INFO "rtc_from4_init: using hardware ECC detection.\n");

	this->ecc.mode = NAND_ECC_HW_SYNDROME;
	this->ecc.size = 512;
	this->ecc.bytes = 8;
	/* return the status of extra status and ECC checks */
	this->errstat = rtc_from4_errstat;
	/* set the nand_oobinfo to support FPGA H/W error detection */
	this->ecc.layout = &rtc_from4_nand_oobinfo;
	this->ecc.hwctl = rtc_from4_enable_hwecc;
	this->ecc.calculate = rtc_from4_calculate_ecc;
	this->ecc.correct = rtc_from4_correct_data;

	/* We could create the decoder on demand, if memory is a concern.
	 * This way we have it handy, if an error happens
	 *
	 * Symbolsize is 10 (bits)
	 * Primitve polynomial is x^10+x^3+1
	 * first consecutive root is 0
	 * primitve element to generate roots = 1
	 * generator polinomial degree = 6
	 */
	rs_decoder = init_rs(10, 0x409, 0, 1, 6);
	if (!rs_decoder) {
		printk(KERN_ERR "Could not create a RS decoder\n");
		ret = -ENOMEM;
		goto err_1;
	}
#else
	printk(KERN_INFO "rtc_from4_init: using software ECC detection.\n");

	this->ecc.mode = NAND_ECC_SOFT;
#endif

	/* set the bad block tables to support debugging */
	this->bbt_td = &rtc_from4_bbt_main_descr;
	this->bbt_md = &rtc_from4_bbt_mirror_descr;

	/* Scan to find existence of the device */
	if (nand_scan(rtc_from4_mtd, RTC_FROM4_MAX_CHIPS)) {
		ret = -ENXIO;
		goto err_2;
	}

	/* Perform 'device recovery' for each chip in case there was a power loss. */
	for (i = 0; i < this->numchips; i++) {
		deplete(rtc_from4_mtd, i);
	}

#if RTC_FROM4_NO_VIRTBLOCKS
	/* use a smaller erase block to minimize wasted space when a block is bad */
	/* note: this uses eight times as much RAM as using the default and makes */
	/*       mounts take four times as long. */
	rtc_from4_mtd->flags |= MTD_NO_VIRTBLOCKS;
#endif

	/* Register the partitions */
	ret = add_mtd_partitions(rtc_from4_mtd, partition_info, NUM_PARTITIONS);
	if (ret)
		goto err_3;

	/* Return happy */
	return 0;
err_3:
	nand_release(rtc_from4_mtd);
err_2:
	free_rs(rs_decoder);
err_1:
	kfree(rtc_from4_mtd);
	return ret;
}

module_init(rtc_from4_init);

/*
 * Clean up routine
 */
static void __exit rtc_from4_cleanup(void)
{
	/* Release resource, unregister partitions */
	nand_release(rtc_from4_mtd);

	/* Free the MTD device structure */
	kfree(rtc_from4_mtd);

#ifdef RTC_FROM4_HWECC
	/* Free the reed solomon resources */
	if (rs_decoder) {
		free_rs(rs_decoder);
	}
#endif
}

module_exit(rtc_from4_cleanup);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("d.marlin <[e-mail]");
MODULE_DESCRIPTION("Board-specific glue layer for AG-AND flash on Renesas FROM_BOARD4");