Commit f0689802 authored by Miquel Raynal's avatar Miquel Raynal
Browse files

mtd: rawnand: micron: Adapt the PAGE READ flow to constraint controllers 



There are controllers not able to just read data cycles on the
bus. There are controllers not able to do a change column.

If we want to support both, we need to check which operation is
supported first. This is the exact same mechanism that is in use for
parameter page reads (ONFI/JEDEC) as the same problem occurs.

Speed testing does not show any throughput penalty so we do not
optimize more than that. However it is likely that, in the future, a
more robust and exhaustive test will run at boot time to avoid
re-checking what is supported and what is not at every call.

Signed-off-by: default avatarMiquel Raynal <miquel.raynal@bootlin.com>
Reviewed-by: default avatarBoris Brezillon <boris.brezillon@collabora.com>
Link: https://lore.kernel.org/linux-mtd/20200519130834.2918-1-miquel.raynal@bootlin.com
parent 767727b9

drivers/mtd/nand/raw/nand_micron.c

+52 −9
Original line number Diff line number Diff line
@@ -192,6 +192,7 @@ static int micron_nand_on_die_ecc_status_4(struct nand_chip *chip, u8 status, 
	struct micron_nand *micron = nand_get_manufacturer_data(chip);

	struct mtd_info *mtd = nand_to_mtd(chip);

	unsigned int step, max_bitflips = 0;

	bool use_datain = false;

	int ret;



	if (!(status & NAND_ECC_STATUS_WRITE_RECOMMENDED)) {
@@ -211,8 +212,27 @@ static int micron_nand_on_die_ecc_status_4(struct nand_chip *chip, u8 status, 
	 * in non-raw mode, even if the user did not request those bytes.

	 */

	if (!oob_required) {

		ret = nand_read_data_op(chip, chip->oob_poi, mtd->oobsize,

					false, false);

		/*

		 * We first check which operation is supported by the controller

		 * before running it. This trick makes it possible to support

		 * all controllers, even the most constraints, without almost

		 * any performance hit.

		 *

		 * TODO: could be enhanced to avoid repeating the same check

		 * over and over in the fast path.

		 */

		if (!nand_has_exec_op(chip) ||

		    !nand_read_data_op(chip, chip->oob_poi, mtd->oobsize, false,

				       true))

			use_datain = true;



		if (use_datain)

			ret = nand_read_data_op(chip, chip->oob_poi,

						mtd->oobsize, false, false);

		else

			ret = nand_change_read_column_op(chip, mtd->writesize,

							 chip->oob_poi,

							 mtd->oobsize, false);

		if (ret)

			return ret;

	}
@@ -285,6 +305,7 @@ micron_nand_read_page_on_die_ecc(struct nand_chip *chip, uint8_t *buf, 
				 int oob_required, int page)

{

	struct mtd_info *mtd = nand_to_mtd(chip);

	bool use_datain = false;

	u8 status;

	int ret, max_bitflips = 0;
@@ -300,14 +321,36 @@ micron_nand_read_page_on_die_ecc(struct nand_chip *chip, uint8_t *buf, 
	if (ret)

		goto out;



	/*

	 * We first check which operation is supported by the controller before

	 * running it. This trick makes it possible to support all controllers,

	 * even the most constraints, without almost any performance hit.

	 *

	 * TODO: could be enhanced to avoid repeating the same check over and

	 * over in the fast path.

	 */

	if (!nand_has_exec_op(chip) ||

	    !nand_read_data_op(chip, buf, mtd->writesize, false, true))

		use_datain = true;



	if (use_datain) {

		ret = nand_exit_status_op(chip);

		if (ret)

			goto out;



	ret = nand_read_data_op(chip, buf, mtd->writesize, false, false);

		ret = nand_read_data_op(chip, buf, mtd->writesize, false,

					false);

		if (!ret && oob_required)

		ret = nand_read_data_op(chip, chip->oob_poi, mtd->oobsize,

					false, false);

			ret = nand_read_data_op(chip, chip->oob_poi,

						mtd->oobsize, false, false);

	} else {

		ret = nand_change_read_column_op(chip, 0, buf, mtd->writesize,

						 false);

		if (!ret && oob_required)

			ret = nand_change_read_column_op(chip, mtd->writesize,

							 chip->oob_poi,

							 mtd->oobsize, false);

	}



	if (chip->ecc.strength == 4)

		max_bitflips = micron_nand_on_die_ecc_status_4(chip, status,

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