[PATCH v2] mtd: fsl_upm: Support NAND ECC DTS properties

[Aaron Sierra <asierra@xes-inc.com>]

From: Jordan Friendshuh <jfriendshuh@xes-inc.com>

Support the generic nand-ecc-mode and nand-ecc-strength device-tree
properties with the Freescale UPM NAND driver.

This patch preserves the default software ECC mode while adding the
ability to use BCH ECC for larger NAND devices.

Signed-off-by: Jordan Friendshuh <jfriendshuh@xes-inc.com>
Signed-off-by: Aaron Sierra <asierra@xes-inc.com>
---
v2:
    * Now using ECC mode and strength helpers from of_mtd.h
    * ECC mode and strength checking is more robust

 .../devicetree/bindings/mtd/fsl-upm-nand.txt       |  2 +
 drivers/mtd/nand/Kconfig                           |  1 +
 drivers/mtd/nand/fsl_upm.c                         | 51 +++++++++++++++++++---
 3 files changed, 49 insertions(+), 5 deletions(-)

diff --git a/Documentation/devicetree/bindings/mtd/fsl-upm-nand.txt b/Documentation/devicetree/bindings/mtd/fsl-upm-nand.txt
index fce4894..a9906f6 100644
--- a/Documentation/devicetree/bindings/mtd/fsl-upm-nand.txt
+++ b/Documentation/devicetree/bindings/mtd/fsl-upm-nand.txt
@@ -18,6 +18,8 @@ Optional properties:
 - chip-delay : chip dependent delay for transferring data from array to
 	read registers (tR). Required if property "gpios" is not used
 	(R/B# pins not connected).
+- nand-ecc-mode : as defined by nand.txt ("soft" and "soft_bch", only).
+- nand-ecc-strength : as defined by nand.txt.
 
 Each flash chip described may optionally contain additional sub-nodes
 describing partitions of the address space. See partition.txt for more
diff --git a/drivers/mtd/nand/Kconfig b/drivers/mtd/nand/Kconfig
index f1cf503..85c0243 100644
--- a/drivers/mtd/nand/Kconfig
+++ b/drivers/mtd/nand/Kconfig
@@ -439,6 +439,7 @@ config MTD_NAND_FSL_UPM
 	tristate "Support for NAND on Freescale UPM"
 	depends on PPC_83xx || PPC_85xx
 	select FSL_LBC
+	select MTD_NAND_ECC_BCH
 	help
 	  Enables support for NAND Flash chips wired onto Freescale PowerPC
 	  processor localbus with User-Programmable Machine support.
diff --git a/drivers/mtd/nand/fsl_upm.c b/drivers/mtd/nand/fsl_upm.c
index 4d203e8..8f38447 100644
--- a/drivers/mtd/nand/fsl_upm.c
+++ b/drivers/mtd/nand/fsl_upm.c
@@ -18,6 +18,7 @@
 #include <linux/mtd/nand_ecc.h>
 #include <linux/mtd/partitions.h>
 #include <linux/mtd/mtd.h>
+#include <linux/of_mtd.h>
 #include <linux/of_address.h>
 #include <linux/of_platform.h>
 #include <linux/of_gpio.h>
@@ -160,6 +161,11 @@ static int fun_chip_init(struct fsl_upm_nand *fun,
 	int ret;
 	struct device_node *flash_np;
 	struct mtd_part_parser_data ppdata;
+	int mode, strength;
+
+	flash_np = of_get_next_child(upm_np, NULL);
+	if (!flash_np)
+		return -ENODEV;
 
 	fun->chip.IO_ADDR_R = fun->io_base;
 	fun->chip.IO_ADDR_W = fun->io_base;
@@ -168,7 +174,46 @@ static int fun_chip_init(struct fsl_upm_nand *fun,
 	fun->chip.read_byte = fun_read_byte;
 	fun->chip.read_buf = fun_read_buf;
 	fun->chip.write_buf = fun_write_buf;
-	fun->chip.ecc.mode = NAND_ECC_SOFT;
+
+	/*
+	 * If nand-ecc-strength < 0, require ECC_SOFT, error otherwise.
+	 * If nand-ecc-strength == 0, error.
+	 * If nand-ecc-strength == 1, require ECC_SOFT, error otherwise.
+	 * If nand-ecc-strength > 1, force ECC_SOFT_BCH (warn on mode mismatch).
+	 */
+	mode = of_get_nand_ecc_mode(flash_np);
+	strength = of_get_nand_ecc_strength(flash_np);
+	if (!of_property_read_bool(flash_np, "nand-ecc-mode")) {
+		dev_info(fun->dev, "ECC mode defaulting to 'soft'");
+		mode = NAND_ECC_SOFT;
+	} else if (mode != NAND_ECC_SOFT && mode != NAND_ECC_SOFT_BCH) {
+		dev_err(fun->dev, "ECC mode in device tree is unsupported");
+		ret = -EINVAL;
+		goto err;
+	}
+
+	/* We know mode is either NAND_ECC_SOFT or NAND_ECC_SOFT_BCH */
+	if (strength < 0 && mode == NAND_ECC_SOFT_BCH) {
+		dev_err(fun->dev,
+			"ECC BCH mode requires nand-ecc-strength property");
+		ret = -EINVAL;
+		goto err;
+	} else if (strength == 0) {
+		dev_err(fun->dev, "ECC strength of 0 bits is unsupported");
+		ret = -EINVAL;
+		goto err;
+	} else if (strength == 1 && mode == NAND_ECC_SOFT_BCH) {
+		dev_err(fun->dev, "ECC BCH mode requires > 1-bit strength");
+		ret = -EINVAL;
+		goto err;
+	} else if (strength > 1 && mode == NAND_ECC_SOFT) {
+		dev_warn(fun->dev,
+			"Forcing ECC BCH due to %d-bit strength\n", strength);
+		mode = NAND_ECC_SOFT_BCH;
+	}
+	fun->chip.ecc.mode = mode;
+	fun->chip.ecc.strength = strength;
+
 	if (fun->mchip_count > 1)
 		fun->chip.select_chip = fun_select_chip;
 
@@ -178,10 +223,6 @@ static int fun_chip_init(struct fsl_upm_nand *fun,
 	fun->mtd.priv = &fun->chip;
 	fun->mtd.owner = THIS_MODULE;
 
-	flash_np = of_get_next_child(upm_np, NULL);
-	if (!flash_np)
-		return -ENODEV;
-
 	fun->mtd.name = kasprintf(GFP_KERNEL, "0x%llx.%s", (u64)io_res->start,
 				  flash_np->name);
 	if (!fun->mtd.name) {
-- 
1.9.1