[PATCH v3 12/15] mtd: rawnand: sunxi: combine contiguous unprotected OOB reads

[James Hilliard]

The randomized-format OOB reader fetches each parity region and the
unprotected tail separately. H6/H616 pack protected user data before the
first ECC step, leaving a contiguous range of parity bytes and tail data.

Combine adjacent parity regions without crossing protected user data,
and include the tail in the final transfer. Keep software de-randomization
separate so each ECC step and the tail retain their existing seed phases
and PIO/DMA representations. The NAND operation parser splits transfers
which exceed the controller SRAM size.

This reduces column commands for OOB reads without changing erased-page
classification, data-only reads or the plain-marker paths.

Signed-off-by: James Hilliard <james.hilliard1 at gmail.com>
---
 drivers/mtd/nand/raw/sunxi_nand.c | 27 ++++++++++++++++++---------
 1 file changed, 18 insertions(+), 9 deletions(-)

diff --git a/drivers/mtd/nand/raw/sunxi_nand.c b/drivers/mtd/nand/raw/sunxi_nand.c
index 6e54d3a92219..bbfed22640c8 100644
--- a/drivers/mtd/nand/raw/sunxi_nand.c
+++ b/drivers/mtd/nand/raw/sunxi_nand.c
@@ -1412,15 +1412,28 @@ static int sunxi_nfc_hw_ecc_read_unprotected_oob(struct nand_chip *nand,
 	int ret, i;
 
 	for (i = 0; i < ecc->steps; i++) {
-		len = sunxi_nfc_user_data_sz(sunxi_nand, i);
 		off = sunxi_get_ecc_offset(sunxi_nand, ecc, i);
+		len = ecc->bytes;
+		/* Keep decoded user data, but combine adjacent parity regions. */
+		while (i + 1 < ecc->steps &&
+		       !sunxi_nfc_user_data_sz(sunxi_nand, i + 1)) {
+			len += ecc->bytes;
+			i++;
+		}
+		if (i + 1 == ecc->steps)
+			len = mtd->oobsize - off;
+
 		ret = nand_change_read_column_op(nand, mtd->writesize + off,
-						 nand->oob_poi + off,
-						 ecc->bytes, false);
+						 nand->oob_poi + off, len, false);
 		if (ret)
 			return ret;
-		/* Preserve each path's normal representation of ECC bytes. */
-		if (!dma) {
+	}
+
+	/* Preserve each path's normal representation of ECC bytes. */
+	if (!dma) {
+		for (i = 0; i < ecc->steps; i++) {
+			len = sunxi_nfc_user_data_sz(sunxi_nand, i);
+			off = sunxi_get_ecc_offset(sunxi_nand, ecc, i);
 			state = sunxi_nfc_randomizer_state(nand, page, true);
 			state = sunxi_nfc_randomizer_step(state, len * 8 + 15);
 			sunxi_nfc_randomize_buf(state, nand->oob_poi + off,
@@ -1431,10 +1444,6 @@ static int sunxi_nfc_hw_ecc_read_unprotected_oob(struct nand_chip *nand,
 	off = sunxi_get_oob_offset(sunxi_nand, ecc, ecc->steps);
 	len = mtd->oobsize - off;
 	if (len) {
-		ret = nand_change_read_column_op(nand, mtd->writesize + off,
-						 nand->oob_poi + off, len, false);
-		if (ret)
-			return ret;
 		/* The unprotected tail uses the page seed and its 15-bit advance. */
 		state = sunxi_nfc_randomizer_state(nand, page, false);
 		state = sunxi_nfc_randomizer_step(state, 15);

-- 
2.53.0