mtd: rawnand: fsl_elbc: Fix none ECC mode

Commit f6424c22 ("mtd: rawnand: fsl_elbc: Make SW ECC work") added
support for specifying ECC mode via DTS and skipping autodetection.

But it broke explicit specification of HW ECC mode in DTS as correct
settings for HW ECC mode are applied only when NONE mode or nothing was
specified in DTS file.

Also it started aliasing NONE mode to be same as when ECC mode was not
specified and disallowed usage of ON_DIE mode.

Fix all these issues. Use autodetection of ECC mode only in case when mode
was really not specified in DTS file by checking that ecc value is invalid.
Set HW ECC settings either when HW ECC was specified in DTS or it was
autodetected. And do not fail when ON_DIE mode is set.

Fixes: f6424c22 ("mtd: rawnand: fsl_elbc: Make SW ECC work")
Signed-off-by: Pali Rohár <pali@kernel.org>
Reviewed-by: Marek Behún <kabel@kernel.org>
Reviewed-by: Marek Behún <kabel@kernel.org>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20220707184328.3845-1-pali@kernel.org

drivers/mtd/nand/raw/fsl_elbc_nand.c

@@ -726,36 +726,40 @@ static int fsl_elbc_attach_chip(struct nand_chip *chip)
 	struct fsl_lbc_regs __iomem *lbc = ctrl->regs;
 	unsigned int al;
 
-	switch (chip->ecc.engine_type) {
 	/*
 	 * if ECC was not chosen in DT, decide whether to use HW or SW ECC from
 	 * CS Base Register
 	 */
-	case NAND_ECC_ENGINE_TYPE_NONE:
+	if (chip->ecc.engine_type == NAND_ECC_ENGINE_TYPE_INVALID) {
 		/* If CS Base Register selects full hardware ECC then use it */
 		if ((in_be32(&lbc->bank[priv->bank].br) & BR_DECC) ==
 		    BR_DECC_CHK_GEN) {
-			chip->ecc.read_page = fsl_elbc_read_page;
-			chip->ecc.write_page = fsl_elbc_write_page;
-			chip->ecc.write_subpage = fsl_elbc_write_subpage;
-
 			chip->ecc.engine_type = NAND_ECC_ENGINE_TYPE_ON_HOST;
-			mtd_set_ooblayout(mtd, &fsl_elbc_ooblayout_ops);
-			chip->ecc.size = 512;
-			chip->ecc.bytes = 3;
-			chip->ecc.strength = 1;
 		} else {
 			/* otherwise fall back to default software ECC */
 			chip->ecc.engine_type = NAND_ECC_ENGINE_TYPE_SOFT;
 			chip->ecc.algo = NAND_ECC_ALGO_HAMMING;
 		}
+	}
+
+	switch (chip->ecc.engine_type) {
+	/* if HW ECC was chosen, setup ecc and oob layout */
+	case NAND_ECC_ENGINE_TYPE_ON_HOST:
+		chip->ecc.read_page = fsl_elbc_read_page;
+		chip->ecc.write_page = fsl_elbc_write_page;
+		chip->ecc.write_subpage = fsl_elbc_write_subpage;
+		mtd_set_ooblayout(mtd, &fsl_elbc_ooblayout_ops);
+		chip->ecc.size = 512;
+		chip->ecc.bytes = 3;
+		chip->ecc.strength = 1;
 		break;
 
-	/* if SW ECC was chosen in DT, we do not need to set anything here */
+	/* if none or SW ECC was chosen, we do not need to set anything here */
+	case NAND_ECC_ENGINE_TYPE_NONE:
 	case NAND_ECC_ENGINE_TYPE_SOFT:
+	case NAND_ECC_ENGINE_TYPE_ON_DIE:
 		break;
 
-	/* should we also implement *_ECC_ENGINE_CONTROLLER to do as above? */
 	default:
 		return -EINVAL;
 	}