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Commit 9748e1d8 authored by Thomas Petazzoni's avatar Thomas Petazzoni Committed by Boris Brezillon
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mtd: nand: add support for Micron on-die ECC 



Now that the core NAND subsystem has support for on-die ECC, this commit
brings the necessary code to support on-die ECC on Micron NANDs.

In micron_nand_init(), we detect if the Micron NAND chip supports on-die
ECC mode, by checking a number of conditions:

 - It must be an ONFI NAND
 - It must be a SLC NAND

 - Enabling *and* disabling on-die ECC must work

 - The on-die ECC must be correcting 4 bits per 512 bytes of data. Some
   Micron NAND chips have an on-die ECC able to correct 8 bits per 512
   bytes of data, but they work slightly differently and therefore we
   don't support them in this patch.

Then, if the on-die ECC cannot be disabled (some Micron NAND have on-die
ECC forcefully enabled), we bail out, as we don't support such
NANDs. Indeed, the implementation of raw_read()/raw_write() make the
assumption that on-die ECC can be disabled. Support for Micron NANDs
with on-die ECC forcefully enabled can easily be added, but in the
absence of such HW for testing, we preferred to simply bail out.

If the on-die ECC is supported, and requested in the Device Tree, then
it is indeed enabled, by using custom implementations of the
->read_page(), ->read_page_raw(), ->write_page() and ->write_page_raw()
operation to properly handle the on-die ECC.

In the non-raw functions, we need to enable the internal ECC engine
before issuing the NAND_CMD_READ0 or NAND_CMD_SEQIN commands, which is
why we set the NAND_ECC_CUSTOM_PAGE_ACCESS option at initialization
time (it asks the NAND core to let the NAND driver issue those
commands).

Signed-off-by: default avatarThomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: default avatarBoris Brezillon <boris.brezillon@free-electrons.com>
parent 4a78cc64

drivers/mtd/nand/nand_micron.c

+216 −0
Original line number Diff line number Diff line
@@ -17,6 +17,12 @@ 


#include <linux/mtd/nand.h>



/*

 * Special Micron status bit that indicates when the block has been

 * corrected by on-die ECC and should be rewritten

 */

#define NAND_STATUS_WRITE_RECOMMENDED	BIT(3)



struct nand_onfi_vendor_micron {

	u8 two_plane_read;

	u8 read_cache;
@@ -66,9 +72,191 @@ static int micron_nand_onfi_init(struct nand_chip *chip) 
	return 0;

}



static int micron_nand_on_die_ooblayout_ecc(struct mtd_info *mtd, int section,

					    struct mtd_oob_region *oobregion)

{

	if (section >= 4)

		return -ERANGE;



	oobregion->offset = (section * 16) + 8;

	oobregion->length = 8;



	return 0;

}



static int micron_nand_on_die_ooblayout_free(struct mtd_info *mtd, int section,

					     struct mtd_oob_region *oobregion)

{

	if (section >= 4)

		return -ERANGE;



	oobregion->offset = (section * 16) + 2;

	oobregion->length = 6;



	return 0;

}



static const struct mtd_ooblayout_ops micron_nand_on_die_ooblayout_ops = {

	.ecc = micron_nand_on_die_ooblayout_ecc,

	.free = micron_nand_on_die_ooblayout_free,

};



static int micron_nand_on_die_ecc_setup(struct nand_chip *chip, bool enable)

{

	u8 feature[ONFI_SUBFEATURE_PARAM_LEN] = { 0, };



	if (enable)

		feature[0] |= ONFI_FEATURE_ON_DIE_ECC_EN;



	return chip->onfi_set_features(nand_to_mtd(chip), chip,

				       ONFI_FEATURE_ON_DIE_ECC, feature);

}



static int

micron_nand_read_page_on_die_ecc(struct mtd_info *mtd, struct nand_chip *chip,

				 uint8_t *buf, int oob_required,

				 int page)

{

	int status;

	int max_bitflips = 0;



	micron_nand_on_die_ecc_setup(chip, true);



	chip->cmdfunc(mtd, NAND_CMD_READ0, 0x00, page);

	chip->cmdfunc(mtd, NAND_CMD_STATUS, -1, -1);

	status = chip->read_byte(mtd);

	if (status & NAND_STATUS_FAIL)

		mtd->ecc_stats.failed++;

	/*

	 * The internal ECC doesn't tell us the number of bitflips

	 * that have been corrected, but tells us if it recommends to

	 * rewrite the block. If it's the case, then we pretend we had

	 * a number of bitflips equal to the ECC strength, which will

	 * hint the NAND core to rewrite the block.

	 */

	else if (status & NAND_STATUS_WRITE_RECOMMENDED)

		max_bitflips = chip->ecc.strength;



	chip->cmdfunc(mtd, NAND_CMD_READ0, -1, -1);



	nand_read_page_raw(mtd, chip, buf, oob_required, page);



	micron_nand_on_die_ecc_setup(chip, false);



	return max_bitflips;

}



static int

micron_nand_write_page_on_die_ecc(struct mtd_info *mtd, struct nand_chip *chip,

				  const uint8_t *buf, int oob_required,

				  int page)

{

	micron_nand_on_die_ecc_setup(chip, true);



	chip->cmdfunc(mtd, NAND_CMD_SEQIN, 0x00, page);

	nand_write_page_raw(mtd, chip, buf, oob_required, page);

	chip->cmdfunc(mtd, NAND_CMD_PAGEPROG, -1, -1);



	micron_nand_on_die_ecc_setup(chip, false);



	return 0;

}



static int

micron_nand_read_page_raw_on_die_ecc(struct mtd_info *mtd,

				     struct nand_chip *chip,

				     uint8_t *buf, int oob_required,

				     int page)

{

	chip->cmdfunc(mtd, NAND_CMD_READ0, 0x00, page);

	nand_read_page_raw(mtd, chip, buf, oob_required, page);



	return 0;

}



static int

micron_nand_write_page_raw_on_die_ecc(struct mtd_info *mtd,

				      struct nand_chip *chip,

				      const uint8_t *buf, int oob_required,

				      int page)

{

	chip->cmdfunc(mtd, NAND_CMD_SEQIN, 0x00, page);

	nand_write_page_raw(mtd, chip, buf, oob_required, page);

	chip->cmdfunc(mtd, NAND_CMD_PAGEPROG, -1, -1);



	return 0;

}



enum {

	/* The NAND flash doesn't support on-die ECC */

	MICRON_ON_DIE_UNSUPPORTED,



	/*

	 * The NAND flash supports on-die ECC and it can be

	 * enabled/disabled by a set features command.

	 */

	MICRON_ON_DIE_SUPPORTED,



	/*

	 * The NAND flash supports on-die ECC, and it cannot be

	 * disabled.

	 */

	MICRON_ON_DIE_MANDATORY,

};



/*

 * Try to detect if the NAND support on-die ECC. To do this, we enable

 * the feature, and read back if it has been enabled as expected. We

 * also check if it can be disabled, because some Micron NANDs do not

 * allow disabling the on-die ECC and we don't support such NANDs for

 * now.

 *

 * This function also has the side effect of disabling on-die ECC if

 * it had been left enabled by the firmware/bootloader.

 */

static int micron_supports_on_die_ecc(struct nand_chip *chip)

{

	u8 feature[ONFI_SUBFEATURE_PARAM_LEN] = { 0, };

	int ret;



	if (chip->onfi_version == 0)

		return MICRON_ON_DIE_UNSUPPORTED;



	if (chip->bits_per_cell != 1)

		return MICRON_ON_DIE_UNSUPPORTED;



	ret = micron_nand_on_die_ecc_setup(chip, true);

	if (ret)

		return MICRON_ON_DIE_UNSUPPORTED;



	chip->onfi_get_features(nand_to_mtd(chip), chip,

				ONFI_FEATURE_ON_DIE_ECC, feature);

	if ((feature[0] & ONFI_FEATURE_ON_DIE_ECC_EN) == 0)

		return MICRON_ON_DIE_UNSUPPORTED;



	ret = micron_nand_on_die_ecc_setup(chip, false);

	if (ret)

		return MICRON_ON_DIE_UNSUPPORTED;



	chip->onfi_get_features(nand_to_mtd(chip), chip,

				ONFI_FEATURE_ON_DIE_ECC, feature);

	if (feature[0] & ONFI_FEATURE_ON_DIE_ECC_EN)

		return MICRON_ON_DIE_MANDATORY;



	/*

	 * Some Micron NANDs have an on-die ECC of 4/512, some other

	 * 8/512. We only support the former.

	 */

	if (chip->onfi_params.ecc_bits != 4)

		return MICRON_ON_DIE_UNSUPPORTED;



	return MICRON_ON_DIE_SUPPORTED;

}



static int micron_nand_init(struct nand_chip *chip)

{

	struct mtd_info *mtd = nand_to_mtd(chip);

	int ondie;

	int ret;



	ret = micron_nand_onfi_init(chip);
@@ -78,6 +266,34 @@ static int micron_nand_init(struct nand_chip *chip) 
	if (mtd->writesize == 2048)

		chip->bbt_options |= NAND_BBT_SCAN2NDPAGE;



	ondie = micron_supports_on_die_ecc(chip);



	if (ondie == MICRON_ON_DIE_MANDATORY) {

		pr_err("On-die ECC forcefully enabled, not supported\n");

		return -EINVAL;

	}



	if (chip->ecc.mode == NAND_ECC_ON_DIE) {

		if (ondie == MICRON_ON_DIE_UNSUPPORTED) {

			pr_err("On-die ECC selected but not supported\n");

			return -EINVAL;

		}



		chip->ecc.options = NAND_ECC_CUSTOM_PAGE_ACCESS;

		chip->ecc.bytes = 8;

		chip->ecc.size = 512;

		chip->ecc.strength = 4;

		chip->ecc.algo = NAND_ECC_BCH;

		chip->ecc.read_page = micron_nand_read_page_on_die_ecc;

		chip->ecc.write_page = micron_nand_write_page_on_die_ecc;

		chip->ecc.read_page_raw =

			micron_nand_read_page_raw_on_die_ecc;

		chip->ecc.write_page_raw =

			micron_nand_write_page_raw_on_die_ecc;



		mtd_set_ooblayout(mtd, &micron_nand_on_die_ooblayout_ops);

	}



	return 0;

}

include/linux/mtd/nand.h

+2 −0
Original line number Diff line number Diff line
@@ -258,6 +258,8 @@ struct nand_chip; 


/* Vendor-specific feature address (Micron) */

#define ONFI_FEATURE_ADDR_READ_RETRY	0x89

#define ONFI_FEATURE_ON_DIE_ECC		0x90

#define   ONFI_FEATURE_ON_DIE_ECC_EN	BIT(3)



/* ONFI subfeature parameters length */

#define ONFI_SUBFEATURE_PARAM_LEN	4