mtd: rawnand: brcmnand: Add support for getting ecc setting from strap

BCMBCA broadband SoC based board design does not specify ecc setting in
dts but rather use the SoC NAND strap info to obtain the ecc strength
and spare area size setting. Add brcm,nand-ecc-use-strap dts propety for
this purpose and update driver to support this option. However these two
options can not be used at the same time.

Signed-off-by: William Zhang <william.zhang@broadcom.com>
Reviewed-by: David Regan <dregan@broadcom.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20240301173308.226004-1-william.zhang@broadcom.com

Author: William Zhang

drivers/mtd/nand/raw/brcmnand/brcmnand.c

@@ -1038,6 +1038,22 @@ static inline int brcmnand_sector_1k_shift(struct brcmnand_controller *ctrl)
 		return -1;
 }
 
+static bool brcmnand_get_sector_size_1k(struct brcmnand_host *host)
+{
+	struct brcmnand_controller *ctrl = host->ctrl;
+	int sector_size_bit = brcmnand_sector_1k_shift(ctrl);
+	u16 acc_control_offs = brcmnand_cs_offset(ctrl, host->cs,
+						  BRCMNAND_CS_ACC_CONTROL);
+	u32 acc_control;
+
+	if (sector_size_bit < 0)
+		return false;
+
+	acc_control = nand_readreg(ctrl, acc_control_offs);
+
+	return ((acc_control & BIT(sector_size_bit)) != 0);
+}
+
 static void brcmnand_set_sector_size_1k(struct brcmnand_host *host, int val)
 {
 	struct brcmnand_controller *ctrl = host->ctrl;
@@ -1055,6 +1071,43 @@ static void brcmnand_set_sector_size_1k(struct brcmnand_host *host, int val)
 	nand_writereg(ctrl, acc_control_offs, tmp);
 }
 
+static int brcmnand_get_spare_size(struct brcmnand_host *host)
+{
+	struct brcmnand_controller *ctrl = host->ctrl;
+	u16 acc_control_offs = brcmnand_cs_offset(ctrl, host->cs,
+						  BRCMNAND_CS_ACC_CONTROL);
+	u32 acc = nand_readreg(ctrl, acc_control_offs);
+
+	return (acc & brcmnand_spare_area_mask(ctrl));
+}
+
+static void brcmnand_get_ecc_settings(struct brcmnand_host *host, struct nand_chip *chip)
+{
+	struct brcmnand_controller *ctrl = host->ctrl;
+	u16 acc_control_offs = brcmnand_cs_offset(ctrl, host->cs,
+						  BRCMNAND_CS_ACC_CONTROL);
+	bool sector_size_1k = brcmnand_get_sector_size_1k(host);
+	int spare_area_size, ecc_level;
+	u32 acc;
+
+	spare_area_size = brcmnand_get_spare_size(host);
+	acc = nand_readreg(ctrl, acc_control_offs);
+	ecc_level = (acc & brcmnand_ecc_level_mask(ctrl)) >> ctrl->ecc_level_shift;
+	if (sector_size_1k)
+		chip->ecc.strength = ecc_level * 2;
+	else if (spare_area_size == 16 && ecc_level == 15)
+		chip->ecc.strength = 1; /* hamming */
+	else
+		chip->ecc.strength = ecc_level;
+
+	if (chip->ecc.size == 0) {
+		if (sector_size_1k)
+			chip->ecc.size = 1024;
+		else
+			chip->ecc.size = 512;
+	}
+}
+
 /***********************************************************************
  * CS_NAND_SELECT
  ***********************************************************************/
@@ -2625,19 +2678,37 @@ static int brcmnand_setup_dev(struct brcmnand_host *host)
 		nanddev_get_memorg(&chip->base);
 	struct brcmnand_controller *ctrl = host->ctrl;
 	struct brcmnand_cfg *cfg = &host->hwcfg;
-	char msg[128];
+	struct device_node *np = nand_get_flash_node(chip);
 	u32 offs, tmp, oob_sector;
+	bool use_strap = false;
+	char msg[128];
 	int ret;
 
 	memset(cfg, 0, sizeof(*cfg));
+	use_strap = of_property_read_bool(np, "brcm,nand-ecc-use-strap");
 
-	ret = of_property_read_u32(nand_get_flash_node(chip),
-				   "brcm,nand-oob-sector-size",
+	/*
+	 * Either nand-ecc-xxx or brcm,nand-ecc-use-strap can be set. Error out
+	 * if both exist.
+	 */
+	if (chip->ecc.strength && use_strap) {
+		dev_err(ctrl->dev,
+			"ECC strap and DT ECC configuration properties are mutually exclusive\n");
+		return -EINVAL;
+	}
+
+	if (use_strap)
+		brcmnand_get_ecc_settings(host, chip);
+
+	ret = of_property_read_u32(np, "brcm,nand-oob-sector-size",
 				   &oob_sector);
 	if (ret) {
-		/* Use detected size */
-		cfg->spare_area_size = mtd->oobsize /
-					(mtd->writesize >> FC_SHIFT);
+		if (use_strap)
+			cfg->spare_area_size = brcmnand_get_spare_size(host);
+		else
+			/* Use detected size */
+			cfg->spare_area_size = mtd->oobsize /
+						(mtd->writesize >> FC_SHIFT);
 	} else {
 		cfg->spare_area_size = oob_sector;
 	}