Patch "mtd: nand: make Samsung SLC NAND usable again" has been added to the 4.12-stable tree

This is a note to let you know that I've just added the patch titled

mtd: nand: make Samsung SLC NAND usable again

to the 4.12-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
mtd-nand-make-samsung-slc-nand-usable-again.patch
and it can be found in the queue-4.12 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: =?UTF-8?q?Lothar=20Wa=C3=9Fmann?= <[email protected]>
Date: Tue, 29 Aug 2017 12:17:12 +0200
Subject: mtd: nand: make Samsung SLC NAND usable again
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

From: Lothar Waßmann <[email protected]>

commit 69fc01296c92814b62dbfba1600fe7ed2ed304f5 upstream.

commit c51d0ac59f24 ("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.

---
 drivers/mtd/nand/nand_base.c |    7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

@@ -3972,10 +3972,13 @@ static void nand_manufacturer_detect(str
 	 * 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);
+	}
 }
 
 /*

Patches currently in stable-queue which might be from [email protected] are

queue-4.12/mtd-nand-make-samsung-slc-nand-usable-again.patch