mtd: nand: Fix data interface configuration logic

When changing from one data interface setting to another, one has to
ensure a specific sequence which is described in the ONFI spec.

One of these constraints is that the CE line has go high after a reset
before a command can be sent with the new data interface setting, which
is not guaranteed by the current implementation.

Rework the nand_reset() function and all the call sites to make sure the
CE line is asserted and released when required.

Also make sure to actually apply the new data interface setting on the
first die.

Signed-off-by: Boris Brezillon <[e-mail]>
Fixes: d8e725dd8311 ("mtd: nand: automate NAND timings selection")
Reviewed-by: Sascha Hauer <[e-mail]>
Tested-by: Marc Gonzalez <[e-mail]>

drivers/mtd/nand/nand_base.c

···
 /**
  * nand_reset - Reset and initialize a NAND device
  * @chip: The NAND chip
+ * @chipnr: Internal die id
  *
  * Returns 0 for success or negative error code otherwise
  */
-int nand_reset(struct nand_chip *chip)
+int nand_reset(struct nand_chip *chip, int chipnr)
 {
 	struct mtd_info *mtd = nand_to_mtd(chip);
 	int ret;
···
 	if (ret)
 		return ret;
 
+	/*
+	 * The CS line has to be released before we can apply the new NAND
+	 * interface settings, hence this weird ->select_chip() dance.
+	 */
+	chip->select_chip(mtd, chipnr);
 	chip->cmdfunc(mtd, NAND_CMD_RESET, -1, -1);
+	chip->select_chip(mtd, -1);
 
+	chip->select_chip(mtd, chipnr);
 	ret = nand_setup_data_interface(chip);
+	chip->select_chip(mtd, -1);
 	if (ret)
 		return ret;
 
···
 	/* Shift to get chip number */
 	chipnr = ofs >> chip->chip_shift;
 
-	chip->select_chip(mtd, chipnr);
-
 	/*
 	 * Reset the chip.
 	 * If we want to check the WP through READ STATUS and check the bit 7
···
 	 * some operation can also clear the bit 7 of status register
 	 * eg. erase/program a locked block
 	 */
-	nand_reset(chip);
+	nand_reset(chip, chipnr);
+
+	chip->select_chip(mtd, chipnr);
 
 	/* Check, if it is write protected */
 	if (nand_check_wp(mtd)) {
···
 	/* Shift to get chip number */
 	chipnr = ofs >> chip->chip_shift;
 
-	chip->select_chip(mtd, chipnr);
-
 	/*
 	 * Reset the chip.
 	 * If we want to check the WP through READ STATUS and check the bit 7
···
 	 * some operation can also clear the bit 7 of status register
 	 * eg. erase/program a locked block
 	 */
-	nand_reset(chip);
+	nand_reset(chip, chipnr);
+
+	chip->select_chip(mtd, chipnr);
 
 	/* Check, if it is write protected */
 	if (nand_check_wp(mtd)) {
···
 	}
 
 	chipnr = (int)(to >> chip->chip_shift);
-	chip->select_chip(mtd, chipnr);
-
-	/* Shift to get page */
-	page = (int)(to >> chip->page_shift);
 
 	/*
 	 * Reset the chip. Some chips (like the Toshiba TC5832DC found in one
···
 	 * if we don't do this. I have no clue why, but I seem to have 'fixed'
 	 * it in the doc2000 driver in August 1999.  dwmw2.
 	 */
-	nand_reset(chip);
+	nand_reset(chip, chipnr);
+
+	chip->select_chip(mtd, chipnr);
+
+	/* Shift to get page */
+	page = (int)(to >> chip->page_shift);
 
 	/* Check, if it is write protected */
 	if (nand_check_wp(mtd)) {
···
 	int i, maf_idx;
 	u8 id_data[8];
 
-	/* Select the device */
-	chip->select_chip(mtd, 0);
-
 	/*
 	 * Reset the chip, required by some chips (e.g. Micron MT29FxGxxxxx)
 	 * after power-up.
 	 */
-	nand_reset(chip);
+	nand_reset(chip, 0);
+
+	/* Select the device */
+	chip->select_chip(mtd, 0);
 
 	/* Send the command for reading device ID */
 	chip->cmdfunc(mtd, NAND_CMD_READID, 0x00, -1);
···
 		return PTR_ERR(type);
 	}
 
+	/* Initialize the ->data_interface field. */
 	ret = nand_init_data_interface(chip);
+	if (ret)
+		return ret;
+
+	/*
+	 * Setup the data interface correctly on the chip and controller side.
+	 * This explicit call to nand_setup_data_interface() is only required
+	 * for the first die, because nand_reset() has been called before
+	 * ->data_interface and ->default_onfi_timing_mode were set.
+	 * For the other dies, nand_reset() will automatically switch to the
+	 * best mode for us.
+	 */
+	ret = nand_setup_data_interface(chip);
 	if (ret)
 		return ret;
 
···
 
 	/* Check for a chip array */
 	for (i = 1; i < maxchips; i++) {
-		chip->select_chip(mtd, i);
 		/* See comment in nand_get_flash_type for reset */
-		nand_reset(chip);
+		nand_reset(chip, i);
+
+		chip->select_chip(mtd, i);
 		/* Send the command for reading device ID */
 		chip->cmdfunc(mtd, NAND_CMD_READID, 0x00, -1);
 		/* Read manufacturer and device IDs */

include/linux/mtd/nand.h

···
 			   int page);
 
 /* Reset and initialize a NAND device */
-int nand_reset(struct nand_chip *chip);
+int nand_reset(struct nand_chip *chip, int chipnr);
 
 /* Free resources held by the NAND device */
 void nand_cleanup(struct nand_chip *chip);