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Date:   Thu, 15 Jun 2023 19:34:13 +0200
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From:   Johan Jonker <jbx6244@gmail.com>
Subject: [PATCH v3 2/3] mtd: rawnand: rockchip-nand-controller: copy hwecc PA
 data to oob_poi buffer
To:     miquel.raynal@bootlin.com
Cc:     richard@nod.at, vigneshr@ti.com, heiko@sntech.de,
        linux-mtd@lists.infradead.org, linux-kernel@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org,
        linux-rockchip@lists.infradead.org, yifeng.zhao@rock-chips.com
References: <0047fc52-bc45-a768-8bdd-c0f12cddc17e@gmail.com>
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Rockchip boot blocks are written per 4 x 512 byte sectors per page.
Each page must have a page address (PA) pointer in OOB to the next page.
Pages are written in a pattern depending on the NAND chip ID.
This logic used to build a page pattern table is not fully disclosed and
is not easy to fit in the MTD framework.
The formula in rk_nfc_write_page_hwecc() function is not correct.
Make hwecc and raw behavior identical.
Generate boot block page address and pattern for hwecc in user space
and copy PA data to/from the already reserved last 4 bytes before EEC
in the chip->oob_poi data layout.

This patch breaks all existing jffs2 users that have free OOB overlap
with the reserved space for PA data.

Signed-off-by: Johan Jonker <jbx6244@gmail.com>
---

Changed V3:
  Change prefixes
  Reword
---
 .../mtd/nand/raw/rockchip-nand-controller.c   | 34 ++++++++++++-------
 1 file changed, 21 insertions(+), 13 deletions(-)

diff --git a/drivers/mtd/nand/raw/rockchip-nand-controller.c b/drivers/mtd/nand/raw/rockchip-nand-controller.c
index 37fc07ba5..5a0468034 100644
--- a/drivers/mtd/nand/raw/rockchip-nand-controller.c
+++ b/drivers/mtd/nand/raw/rockchip-nand-controller.c
@@ -598,7 +598,7 @@ static int rk_nfc_write_page_hwecc(struct nand_chip *chip, const u8 *buf,
 	int pages_per_blk = mtd->erasesize / mtd->writesize;
 	int ret = 0, i, boot_rom_mode = 0;
 	dma_addr_t dma_data, dma_oob;
-	u32 reg;
+	u32 tmp;
 	u8 *oob;

 	nand_prog_page_begin_op(chip, page, 0, NULL, 0);
@@ -625,6 +625,13 @@ static int rk_nfc_write_page_hwecc(struct nand_chip *chip, const u8 *buf,
 	 *
 	 *   0xFF 0xFF 0xFF 0xFF | BBM OOB1 OOB2 OOB3 | ...
 	 *
+	 * The code here just swaps the first 4 bytes with the last
+	 * 4 bytes without losing any data.
+	 *
+	 * The chip->oob_poi data layout:
+	 *
+	 *    BBM  OOB1 OOB2 OOB3 |......|  PA0  PA1  PA2  PA3
+	 *
 	 * Configure the ECC algorithm supported by the boot ROM.
 	 */
 	if ((page < (pages_per_blk * rknand->boot_blks)) &&
@@ -635,21 +642,17 @@ static int rk_nfc_write_page_hwecc(struct nand_chip *chip, const u8 *buf,
 	}

 	for (i = 0; i < ecc->steps; i++) {
-		if (!i) {
-			reg = 0xFFFFFFFF;
-		} else {
+		if (!i)
+			oob = chip->oob_poi + (ecc->steps - 1) * NFC_SYS_DATA_SIZE;
+		else
 			oob = chip->oob_poi + (i - 1) * NFC_SYS_DATA_SIZE;
-			reg = oob[0] | oob[1] << 8 | oob[2] << 16 |
-			      oob[3] << 24;
-		}

-		if (!i && boot_rom_mode)
-			reg = (page & (pages_per_blk - 1)) * 4;
+		tmp = oob[0] | oob[1] << 8 | oob[2] << 16 | oob[3] << 24;

 		if (nfc->cfg->type == NFC_V9)
-			nfc->oob_buf[i] = reg;
+			nfc->oob_buf[i] = tmp;
 		else
-			nfc->oob_buf[i * (oob_step / 4)] = reg;
+			nfc->oob_buf[i * (oob_step / 4)] = tmp;
 	}

 	dma_data = dma_map_single(nfc->dev, (void *)nfc->page_buf,
@@ -812,12 +815,17 @@ static int rk_nfc_read_page_hwecc(struct nand_chip *chip, u8 *buf, int oob_on,
 		goto timeout_err;
 	}

-	for (i = 1; i < ecc->steps; i++) {
-		oob = chip->oob_poi + (i - 1) * NFC_SYS_DATA_SIZE;
+	for (i = 0; i < ecc->steps; i++) {
+		if (!i)
+			oob = chip->oob_poi + (ecc->steps - 1) * NFC_SYS_DATA_SIZE;
+		else
+			oob = chip->oob_poi + (i - 1) * NFC_SYS_DATA_SIZE;
+
 		if (nfc->cfg->type == NFC_V9)
 			tmp = nfc->oob_buf[i];
 		else
 			tmp = nfc->oob_buf[i * (oob_step / 4)];
+
 		*oob++ = (u8)tmp;
 		*oob++ = (u8)(tmp >> 8);
 		*oob++ = (u8)(tmp >> 16);
--
2.30.2