mtd: rawnand: meson: read/write access for boot ROM pages

Boot ROM on Meson needs some pages to be read/written in a special mode:
384 byte ECC mode (so called "short" by Amlogic) and with scrambling
enabled. Such pages are located on the chip in the following way (for
example):

[ p0 ][ p1 ][ p2 ][ p3 ][ p4 ][ p5 ][ p6 ][ p7 ] ... [ pN ]
  ^           ^           ^           ^

pX is page number "X". "^" means "special" page used by boot ROM - e.g.
every 2nd page in the range of [0, 7]. Step (2 here) and last page in
range is read from the device tree.
Signed-off-by: Arseniy Krasnov <avkrasnov@salutedevices.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20240507230903.3399594-4-avkrasnov@salutedevices.com

drivers/mtd/nand/raw/meson_nand.c

@@ -35,6 +35,7 @@
 #define NFC_CMD_RB		BIT(20)
 #define NFC_CMD_SCRAMBLER_ENABLE	BIT(19)
 #define NFC_CMD_SCRAMBLER_DISABLE	0
+#define NFC_CMD_SHORTMODE_ENABLE	1
 #define NFC_CMD_SHORTMODE_DISABLE	0
 #define NFC_CMD_RB_INT		BIT(14)
 #define NFC_CMD_RB_INT_NO_PIN	((0xb << 10) | BIT(18) | BIT(16))
@@ -78,6 +79,8 @@
 #define DMA_DIR(dir)		((dir) ? NFC_CMD_N2M : NFC_CMD_M2N)
 #define DMA_ADDR_ALIGN		8
 
+#define NFC_SHORT_MODE_ECC_SZ	384
+
 #define ECC_CHECK_RETURN_FF	(-1)
 
 #define NAND_CE0		(0xe << 10)
@@ -125,6 +128,8 @@ struct meson_nfc_nand_chip {
 	u32 twb;
 	u32 tadl;
 	u32 tbers_max;
+	u32 boot_pages;
+	u32 boot_page_step;
 
 	u32 bch_mode;
 	u8 *data_buf;
@@ -298,33 +303,46 @@ static void meson_nfc_cmd_seed(struct meson_nfc *nfc, u32 seed)
 	       nfc->reg_base + NFC_REG_CMD);
 }
 
+static int meson_nfc_is_boot_page(struct nand_chip *nand, int page)
+{
+	const struct meson_nfc_nand_chip *meson_chip = to_meson_nand(nand);
+
+	return (nand->options & NAND_IS_BOOT_MEDIUM) &&
+	       !(page % meson_chip->boot_page_step) &&
+	       (page < meson_chip->boot_pages);
+}
+
 static void meson_nfc_cmd_access(struct nand_chip *nand, int raw, bool dir, int page)
 {
+	const struct meson_nfc_nand_chip *meson_chip = to_meson_nand(nand);
 	struct mtd_info *mtd = nand_to_mtd(nand);
 	struct meson_nfc *nfc = nand_get_controller_data(mtd_to_nand(mtd));
-	struct meson_nfc_nand_chip *meson_chip = to_meson_nand(nand);
-	u32 bch = meson_chip->bch_mode, cmd;
 	int len = mtd->writesize, pagesize, pages;
 	int scrambler;
+	u32 cmd;
 
 	if (nand->options & NAND_NEED_SCRAMBLING)
 		scrambler = NFC_CMD_SCRAMBLER_ENABLE;
 	else
 		scrambler = NFC_CMD_SCRAMBLER_DISABLE;
 
-	pagesize = nand->ecc.size;
-
 	if (raw) {
 		len = mtd->writesize + mtd->oobsize;
 		cmd = len | scrambler | DMA_DIR(dir);
-		writel(cmd, nfc->reg_base + NFC_REG_CMD);
-		return;
-	}
+	} else if (meson_nfc_is_boot_page(nand, page)) {
+		pagesize = NFC_SHORT_MODE_ECC_SZ >> 3;
+		pages = mtd->writesize / 512;
 
+		scrambler = NFC_CMD_SCRAMBLER_ENABLE;
+		cmd = CMDRWGEN(DMA_DIR(dir), scrambler, NFC_ECC_BCH8_1K,
+			       NFC_CMD_SHORTMODE_ENABLE, pagesize, pages);
+	} else {
+		pagesize = nand->ecc.size >> 3;
 		pages = len / nand->ecc.size;
 
-	cmd = CMDRWGEN(DMA_DIR(dir), scrambler, bch,
+		cmd = CMDRWGEN(DMA_DIR(dir), scrambler, meson_chip->bch_mode,
 			       NFC_CMD_SHORTMODE_DISABLE, pagesize, pages);
+	}
 
 	if (scrambler == NFC_CMD_SCRAMBLER_ENABLE)
 		meson_nfc_cmd_seed(nfc, page);
@@ -1425,6 +1443,26 @@ meson_nfc_nand_chip_init(struct device *dev,
 	if (ret)
 		return ret;
 
+	if (nand->options & NAND_IS_BOOT_MEDIUM) {
+		ret = of_property_read_u32(np, "amlogic,boot-pages",
+					   &meson_chip->boot_pages);
+		if (ret) {
+			dev_err(dev, "could not retrieve 'amlogic,boot-pages' property: %d",
+				ret);
+			nand_cleanup(nand);
+			return ret;
+		}
+
+		ret = of_property_read_u32(np, "amlogic,boot-page-step",
+					   &meson_chip->boot_page_step);
+		if (ret) {
+			dev_err(dev, "could not retrieve 'amlogic,boot-page-step' property: %d",
+				ret);
+			nand_cleanup(nand);
+			return ret;
+		}
+	}
+
 	ret = mtd_device_register(mtd, NULL, 0);
 	if (ret) {
 		dev_err(dev, "failed to register MTD device: %d\n", ret);