[PATCH 7/7] mtd: rawnand: brcmnand: Add support for getting ecc setting from strap

[Linus Walleij]

From: William Zhang <william.zhang at broadcom.com>

Backport from the upstream Linux kernel
commit c2cf7e25eb2a3c915a420fb8ceed8912add7f36c
"mtd: rawnand: brcmnand: Add support for getting ecc setting from strap"

Note: the upstream kernel introduces a new
bool brcmnand_get_sector_size_1k() function because the int
version in U-Boot has been removed in Linux. I kept the old
int-returning version that is already in U-Boot as we depend
on that in other code.

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 at broadcom.com>
Reviewed-by: David Regan <dregan at broadcom.com>
Signed-off-by: Miquel Raynal <miquel.raynal at bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20240301173308.226004-1-william.zhang@broadcom.com
Signed-off-by: Linus Walleij <linus.walleij at linaro.org>
---
 drivers/mtd/nand/raw/brcmnand/brcmnand.c | 70 ++++++++++++++++++++++++++++++--
 1 file changed, 66 insertions(+), 4 deletions(-)

diff --git a/drivers/mtd/nand/raw/brcmnand/brcmnand.c b/drivers/mtd/nand/raw/brcmnand/brcmnand.c
index 55d5d27438a8..1ffd6cfff98f 100644
--- a/drivers/mtd/nand/raw/brcmnand/brcmnand.c
+++ b/drivers/mtd/nand/raw/brcmnand/brcmnand.c
@@ -980,6 +980,43 @@ 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
  ***********************************************************************/
@@ -2323,12 +2360,33 @@ static int brcmnand_setup_dev(struct brcmnand_host *host)
 	struct nand_memory_organization *memorg = nanddev_get_memorg(nanddev);
 	struct brcmnand_controller *ctrl = host->ctrl;
 	struct brcmnand_cfg *cfg = &host->hwcfg;
-	char msg[128];
 	u32 offs, tmp, oob_sector;
+	bool use_strap = false;
+	char msg[128];
 	int ret;
 
 	memset(cfg, 0, sizeof(*cfg));
 
+#ifndef __UBOOT__
+	use_strap = of_property_read_bool(nand_get_flash_node(chip),
+					  "brcm,nand-ecc-use-strap"):
+#else
+	ret = ofnode_read_bool(nand_get_flash_node(chip),
+			       "brcm,nand-ecc-use-strap");
+#endif /* __UBOOT__ */
+	/*
+	 * 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);
+
 #ifndef __UBOOT__
 	ret = of_property_read_u32(nand_get_flash_node(chip),
 				   "brcm,nand-oob-sector-size",
@@ -2338,10 +2396,14 @@ static int brcmnand_setup_dev(struct brcmnand_host *host)
 			      "brcm,nand-oob-sector-size",
 			      &oob_sector);
 #endif /* __UBOOT__ */
+
 	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;
 	}

-- 
2.46.0