mtd: nand: make Samsung SLC NAND usable again

commit 69fc0129 upstream.

commit c51d0ac5 ("mtd: nand: Move Samsung specific init/detection
logic in nand_samsung.c") introduced a regression for Samsung SLC NAND
chips. Prior to this commit chip->bits_per_cell was initialized by calling
nand_get_bits_per_cell() before using nand_is_slc().
With the offending commit this call is skipped, leaving
chip->bits_per_cell cleared to zero when the manufacturer specific
'.detect' function calls nand_is_slc() which in turn interprets
bits_per_cell != 1 as indication for an MLC chip.
The effect is that e.g. a K9F1G08U0F NAND chip is falsely detected as
MLC NAND with 4KiB page size rather than SLC with 2KiB page size.

Add a call to nand_get_bits_per_cell() before calling the .detect hook
function in nand_manufacturer_detect(), so that the nand_is_slc()
calls in the manufacturer specific code will return correct results.

Fixes: c51d0ac5 ("mtd: nand: Move Samsung specific init/detection logic in nand_samsung.c")
Signed-off-by: Lothar Waßmann <LW@KARO-electronics.de>
Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/mtd/nand/nand_base.c

@@ -3972,10 +3972,13 @@ static void nand_manufacturer_detect(struct nand_chip *chip)
 	 * nand_decode_ext_id() otherwise.
 	 */
 	if (chip->manufacturer.desc && chip->manufacturer.desc->ops &&
-	    chip->manufacturer.desc->ops->detect)
+	    chip->manufacturer.desc->ops->detect) {
+		/* The 3rd id byte holds MLC / multichip data */
+		chip->bits_per_cell = nand_get_bits_per_cell(chip->id.data[2]);
 		chip->manufacturer.desc->ops->detect(chip);
-	else
+	} else {
 		nand_decode_ext_id(chip);
+	}
 }
 
 /*