mtd: nand: samsung: Retrieve ECC requirements from extended ID

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Gitweb:     http://git.infradead.org/?p=mtd-2.6.git;a=commit;h=8fc82d456e40a073d7e85d7825a345698f4b5a40
Commit:     8fc82d456e40a073d7e85d7825a345698f4b5a40
Parent:     3b5206f4be9b65d2f0f85b3239cf117a1d0de7ce
Author:     Hans de Goede <hdegoede at redhat.com>
AuthorDate: Wed Jun 8 10:45:28 2016 +0200
Committer:  Boris Brezillon <boris.brezillon at free-electrons.com>
CommitDate: Wed Mar 8 23:21:23 2017 +0100

    mtd: nand: samsung: Retrieve ECC requirements from extended ID
    
    On some nand controllers with hw-ecc the controller code wants to know
    the ecc strength and size and having these as 0, 0 is not accepted.
    
    Specifying these in devicetree is possible but undesirable as the nand
    may be different in different production runs of the same board, so it
    is better to get this info from the nand id where possible.
    
    This commit adds code to read the ecc strength and size from the nand
    for Samsung extended-id nands. This code is based on the info for the 5th
    id byte in the datasheets for the following Samsung nands: K9GAG08U0E,
    K9GAG08U0F, K9GAG08X0D, K9GBG08U0A, K9GBG08U0B. These all use these bits
    in the exact same way.
    
    Signed-off-by: Hans de Goede <hdegoede at redhat.com>
    Acked-by: Richard Weinberger <richard at nod.at>
    Signed-off-by: Boris Brezillon <boris.brezillon at free-electrons.com>
---
 drivers/mtd/nand/nand_samsung.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/drivers/mtd/nand/nand_samsung.c b/drivers/mtd/nand/nand_samsung.c
index 5c259dd..9cfc403 100644
--- a/drivers/mtd/nand/nand_samsung.c
+++ b/drivers/mtd/nand/nand_samsung.c
@@ -66,6 +66,26 @@ static void samsung_nand_decode_id(struct nand_chip *chip)
 		extid >>= 2;
 		mtd->erasesize = (128 * 1024) <<
 				 (((extid >> 1) & 0x04) | (extid & 0x03));
+
+		/* Extract ECC requirements from 5th id byte*/
+		extid = (chip->id.data[4] >> 4) & 0x07;
+		if (extid < 5) {
+			chip->ecc_step_ds = 512;
+			chip->ecc_strength_ds = 1 << extid;
+		} else {
+			chip->ecc_step_ds = 1024;
+			switch (extid) {
+			case 5:
+				chip->ecc_strength_ds = 24;
+				break;
+			case 6:
+				chip->ecc_strength_ds = 40;
+				break;
+			case 7:
+				chip->ecc_strength_ds = 60;
+				break;
+			}
+		}
 	} else {
 		nand_decode_ext_id(chip);
 	}