mtd: spinand: Introduce a way to avoid raw access

SkyHigh spinand device has ECC enable bit in configuration register but
it must be always enabled. If ECC is disabled, read and write ops
results in undetermined state. For such devices, a way to avoid raw
access is needed.

Introduce SPINAND_NO_RAW_ACCESS flag to advertise the device does not
support raw access. In such devices, the on-die ECC engine ops returns
error to I/O request in raw mode.

Checking and marking BBM need to be cared as special case, by adding
fallback mechanism that tries read/write OOB with ECC enabled.

Signed-off-by: Takahiro Kuwano <[email protected]>
Signed-off-by: Miquel Raynal <[email protected]>

Author: Kuwano-san

drivers/mtd/nand/spi/core.c

@@ -294,6 +294,9 @@ static int spinand_ondie_ecc_prepare_io_req(struct nand_device *nand,
 	struct spinand_device *spinand = nand_to_spinand(nand);
 	bool enable = (req->mode != MTD_OPS_RAW);
 
+	if (!enable && spinand->flags & SPINAND_NO_RAW_ACCESS)
+		return -EOPNOTSUPP;
+
 	memset(spinand->oobbuf, 0xff, nanddev_per_page_oobsize(nand));
 
 	/* Only enable or disable the engine */
@@ -901,9 +904,17 @@ static bool spinand_isbad(struct nand_device *nand, const struct nand_pos *pos)
 		.oobbuf.in = marker,
 		.mode = MTD_OPS_RAW,
 	};
+	int ret;
 
 	spinand_select_target(spinand, pos->target);
-	spinand_read_page(spinand, &req);
+
+	ret = spinand_read_page(spinand, &req);
+	if (ret == -EOPNOTSUPP) {
+		/* Retry with ECC in case raw access is not supported */
+		req.mode = MTD_OPS_PLACE_OOB;
+		spinand_read_page(spinand, &req);
+	}
+
 	if (marker[0] != 0xff || marker[1] != 0xff)
 		return true;
 
@@ -942,7 +953,14 @@ static int spinand_markbad(struct nand_device *nand, const struct nand_pos *pos)
 	if (ret)
 		return ret;
 
-	return spinand_write_page(spinand, &req);
+	ret = spinand_write_page(spinand, &req);
+	if (ret == -EOPNOTSUPP) {
+		/* Retry with ECC in case raw access is not supported */
+		req.mode = MTD_OPS_PLACE_OOB;
+		ret = spinand_write_page(spinand, &req);
+	}
+
+	return ret;
 }
 
 static int spinand_mtd_block_markbad(struct mtd_info *mtd, loff_t offs)

include/linux/mtd/spinand.h

@@ -314,6 +314,7 @@ struct spinand_ecc_info {
 #define SPINAND_HAS_CR_FEAT_BIT		BIT(1)
 #define SPINAND_HAS_PROG_PLANE_SELECT_BIT		BIT(2)
 #define SPINAND_HAS_READ_PLANE_SELECT_BIT		BIT(3)
+#define SPINAND_NO_RAW_ACCESS				BIT(4)
 
 /**
  * struct spinand_ondie_ecc_conf - private SPI-NAND on-die ECC engine structure