[PATCH 3/3] mtd: rawnand: sunxi: select the packed H6/H616 OOB layout

[James Hilliard]

The H6/H616 controller can configure a separate protected user-data
length for every ECC step. Mainline fills all space left after ECC with
user data. This changes the physical ECC offsets from those used by
Allwinner NAND firmware, so pages written by one layout cannot be
decoded with the other.

The allwinner,randomized-oob property selects the randomized normal-page
OOB format. When it is present on H6/H616, use four protected user-data
bytes per 1 KiB ECC step, cap the total at 16 bytes, and assign the
entire total to ECC step zero. Reserve the same total before maximizing
ECC strength so the selected strength leaves enough room.

Keep the existing maximized mainline user-data layout when the property
is absent. Older controllers have fixed four-byte user-data registers
and need no additional placement change.

Signed-off-by: James Hilliard <james.hilliard1@xxxxxxxxx>
---
 drivers/mtd/nand/raw/sunxi_nand.c | 31 +++++++++++++++++++++++++------
 1 file changed, 25 insertions(+), 6 deletions(-)

diff --git a/drivers/mtd/nand/raw/sunxi_nand.c b/drivers/mtd/nand/raw/sunxi_nand.c
index 92b26371a6d1..2388cc361685 100644
--- a/drivers/mtd/nand/raw/sunxi_nand.c
+++ b/drivers/mtd/nand/raw/sunxi_nand.c
@@ -223,6 +223,9 @@
  */
 #define USER_DATA_SZ 4
 
+/* The randomized H6/H616 layout packs at most 16 bytes before ECC step 0. */
+#define SUNXI_NFC_H6_MAX_USER_DATA_SZ 16
+
 /**
  * struct sunxi_nand_chip_sel - stores information related to NAND Chip Select
  *
@@ -2036,8 +2039,14 @@ static void sunxi_nand_detach_chip(struct nand_chip *nand)
 	sunxi_nand->user_data_bytes = NULL;
 }
 
-static int sunxi_nfc_maximize_user_data(struct nand_chip *nand, uint32_t oobsize,
-					int ecc_bytes, int nsectors)
+static unsigned int sunxi_nfc_h6_user_data_sz(int nsectors)
+{
+	return min(nsectors * USER_DATA_SZ,
+		   SUNXI_NFC_H6_MAX_USER_DATA_SZ);
+}
+
+static int sunxi_nfc_init_user_data(struct nand_chip *nand, uint32_t oobsize,
+				    int ecc_bytes, int nsectors)
 {
 	struct sunxi_nand_chip *sunxi_nand = to_sunxi_nand(nand);
 	struct sunxi_nfc *nfc = to_sunxi_nfc(nand->controller);
@@ -2050,6 +2059,12 @@ static int sunxi_nfc_maximize_user_data(struct nand_chip *nand, uint32_t oobsize
 	if (!sunxi_nand->user_data_bytes)
 		return -ENOMEM;
 
+	if (sunxi_nand->randomized_oob) {
+		sunxi_nand->user_data_bytes[0] =
+			sunxi_nfc_h6_user_data_sz(nsectors);
+		return 0;
+	}
+
 	for (step = 0; (step < nsectors) && (remaining_bytes > 0); step++) {
 		for (i = 0; i < c->nuser_data_tab; i++) {
 			if (c->user_data_len_tab[i] > remaining_bytes)
@@ -2104,6 +2119,10 @@ static int sunxi_nand_hw_ecc_ctrl_init(struct nand_chip *nand,
 				bytes -= 2;
 
 			bytes -= total_user_data_sz;
+		} else if (sunxi_nand->randomized_oob) {
+			total_user_data_sz =
+				sunxi_nfc_h6_user_data_sz(nsectors);
+			bytes -= total_user_data_sz;
 		} else {
 			/*
 			 * remove at least the BBM size before computing the
@@ -2170,12 +2189,12 @@ static int sunxi_nand_hw_ecc_ctrl_init(struct nand_chip *nand,
 	nsectors = mtd->writesize / ecc->size;
 
 	/*
-	 * The rationale for variable data length is to prioritize maximum ECC
-	 * strength, and then use the remaining space for user data.
+	 * The default variable-length layout prioritizes maximum ECC strength,
+	 * then uses the remaining space for user data.
 	 */
 	if (nfc->caps->reg_user_data_len)
-		sunxi_nfc_maximize_user_data(nand, mtd->oobsize, ecc->bytes,
-					     nsectors);
+		sunxi_nfc_init_user_data(nand, mtd->oobsize, ecc->bytes,
+					 nsectors);
 
 	if (total_user_data_sz == 0)
 		for (i = 0; i < nsectors; i++)

-- 
2.53.0