[PATCH 2/6] mtd: nand: gpmc: Add support for ELM

[Sascha Hauer <s.hauer@pengutronix.de>]

This adds support for the ELM (Error Location Module) found on
not-too-old OMAP SoCs. The driver has been taken from Linux-5.3-rc6
with interrupt support removed.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
---
 drivers/mtd/nand/Kconfig    |  10 +
 drivers/mtd/nand/Makefile   |   1 +
 drivers/mtd/nand/omap_elm.c | 413 ++++++++++++++++++++++++++++++++++++
 include/platform_data/elm.h |  53 +++++
 4 files changed, 477 insertions(+)
 create mode 100644 drivers/mtd/nand/omap_elm.c
 create mode 100644 include/platform_data/elm.h

diff --git a/drivers/mtd/nand/Kconfig b/drivers/mtd/nand/Kconfig
index 2b4a478a03..fadfe1f99b 100644
--- a/drivers/mtd/nand/Kconfig
+++ b/drivers/mtd/nand/Kconfig
@@ -90,6 +90,16 @@ config NAND_OMAP_GPMC
 	  Support for NAND flash using GPMC. GPMC is a common memory
 	  interface found on Texas Instrument's OMAP platforms
 
+config MTD_NAND_OMAP_ELM
+	bool "Support for ELM (Error Location Module) on OMAP platforms"
+	depends on NAND_OMAP_GPMC
+	help
+	  This config enables the ELM hardware engine, which can be used to
+	  locate and correct errors when using BCH ECC scheme. This offloads
+	  the cpu from doing ECC error searching and correction. However some
+	  legacy OMAP families like OMAP2xxx, OMAP3xxx do not have ELM engine
+	  so this is optional for them.
+
 config NAND_ORION
 	bool
 	prompt "Marvell Orion NAND driver"
diff --git a/drivers/mtd/nand/Makefile b/drivers/mtd/nand/Makefile
index 6088512745..a4066ba778 100644
--- a/drivers/mtd/nand/Makefile
+++ b/drivers/mtd/nand/Makefile
@@ -10,6 +10,7 @@ obj-$(CONFIG_MTD_NAND_NOMADIK)		+= nomadik_nand.o
 obj-$(CONFIG_NAND_IMX)			+= nand_imx.o
 obj-$(CONFIG_NAND_IMX_BBM)		+= nand_imx_bbm.o
 obj-$(CONFIG_NAND_OMAP_GPMC)		+= nand_omap_gpmc.o nand_omap_bch_decoder.o
+obj-$(CONFIG_MTD_NAND_OMAP_ELM)		+= omap_elm.o
 obj-$(CONFIG_NAND_ORION)		+= nand_orion.o
 obj-$(CONFIG_NAND_MRVL_NFC)		+= nand_mrvl_nfc.o
 obj-$(CONFIG_NAND_ATMEL)		+= atmel_nand.o
diff --git a/drivers/mtd/nand/omap_elm.c b/drivers/mtd/nand/omap_elm.c
new file mode 100644
index 0000000000..583235fc78
--- /dev/null
+++ b/drivers/mtd/nand/omap_elm.c
@@ -0,0 +1,413 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Error Location Module
+ *
+ * Copyright (C) 2012 Texas Instruments Incorporated - http://www.ti.com/
+ */
+
+#define DRIVER_NAME	"omap-elm"
+
+#include <common.h>
+#include <driver.h>
+#include <init.h>
+#include <platform_data/elm.h>
+
+#define ELM_SYSCONFIG			0x010
+#define ELM_IRQSTATUS			0x018
+#define ELM_IRQENABLE			0x01c
+#define ELM_LOCATION_CONFIG		0x020
+#define ELM_PAGE_CTRL			0x080
+#define ELM_SYNDROME_FRAGMENT_0		0x400
+#define ELM_SYNDROME_FRAGMENT_1		0x404
+#define ELM_SYNDROME_FRAGMENT_2		0x408
+#define ELM_SYNDROME_FRAGMENT_3		0x40c
+#define ELM_SYNDROME_FRAGMENT_4		0x410
+#define ELM_SYNDROME_FRAGMENT_5		0x414
+#define ELM_SYNDROME_FRAGMENT_6		0x418
+#define ELM_LOCATION_STATUS		0x800
+#define ELM_ERROR_LOCATION_0		0x880
+
+/* ELM Interrupt Status Register */
+#define INTR_STATUS_PAGE_VALID		BIT(8)
+
+/* ELM Interrupt Enable Register */
+#define INTR_EN_PAGE_MASK		BIT(8)
+
+/* ELM Location Configuration Register */
+#define ECC_BCH_LEVEL_MASK		0x3
+
+/* ELM syndrome */
+#define ELM_SYNDROME_VALID		BIT(16)
+
+/* ELM_LOCATION_STATUS Register */
+#define ECC_CORRECTABLE_MASK		BIT(8)
+#define ECC_NB_ERRORS_MASK		0x1f
+
+/* ELM_ERROR_LOCATION_0-15 Registers */
+#define ECC_ERROR_LOCATION_MASK		0x1fff
+
+#define ELM_ECC_SIZE			0x7ff
+
+#define SYNDROME_FRAGMENT_REG_SIZE	0x40
+#define ERROR_LOCATION_SIZE		0x100
+
+struct elm_registers {
+	u32 elm_irqenable;
+	u32 elm_sysconfig;
+	u32 elm_location_config;
+	u32 elm_page_ctrl;
+	u32 elm_syndrome_fragment_6[ERROR_VECTOR_MAX];
+	u32 elm_syndrome_fragment_5[ERROR_VECTOR_MAX];
+	u32 elm_syndrome_fragment_4[ERROR_VECTOR_MAX];
+	u32 elm_syndrome_fragment_3[ERROR_VECTOR_MAX];
+	u32 elm_syndrome_fragment_2[ERROR_VECTOR_MAX];
+	u32 elm_syndrome_fragment_1[ERROR_VECTOR_MAX];
+	u32 elm_syndrome_fragment_0[ERROR_VECTOR_MAX];
+};
+
+struct elm_info {
+	struct device_d *dev;
+	void __iomem *elm_base;
+	struct list_head list;
+	enum bch_ecc bch_type;
+	struct elm_registers elm_regs;
+	int ecc_steps;
+	int ecc_syndrome_size;
+};
+
+static struct elm_info *ginfo;
+
+static void elm_write_reg(struct elm_info *info, int offset, u32 val)
+{
+	writel(val, info->elm_base + offset);
+}
+
+static u32 elm_read_reg(struct elm_info *info, int offset)
+{
+	return readl(info->elm_base + offset);
+}
+
+/**
+ * elm_config - Configure ELM module
+ * @dev:	ELM device
+ * @bch_type:	Type of BCH ecc
+ */
+int elm_config(enum bch_ecc bch_type, int ecc_steps, int ecc_step_size,
+		int ecc_syndrome_size)
+{
+	struct elm_info *info = ginfo;
+	u32 reg_val;
+
+	if (!info)
+		return -ENODEV;
+	/* ELM cannot detect ECC errors for chunks > 1KB */
+	if (ecc_step_size > ((ELM_ECC_SIZE + 1) / 2)) {
+		dev_err(info->dev, "unsupported config ecc-size=%d\n", ecc_step_size);
+		return -EINVAL;
+	}
+	/* ELM support 8 error syndrome process */
+	if (ecc_steps > ERROR_VECTOR_MAX) {
+		dev_err(info->dev, "unsupported config ecc-step=%d\n", ecc_steps);
+		return -EINVAL;
+	}
+
+	reg_val = (bch_type & ECC_BCH_LEVEL_MASK) | (ELM_ECC_SIZE << 16);
+	elm_write_reg(info, ELM_LOCATION_CONFIG, reg_val);
+	info->bch_type		= bch_type;
+	info->ecc_steps		= ecc_steps;
+	info->ecc_syndrome_size	= ecc_syndrome_size;
+
+	return 0;
+}
+
+/**
+ * elm_configure_page_mode - Enable/Disable page mode
+ * @info:	elm info
+ * @index:	index number of syndrome fragment vector
+ * @enable:	enable/disable flag for page mode
+ *
+ * Enable page mode for syndrome fragment index
+ */
+static void elm_configure_page_mode(struct elm_info *info, int index,
+		bool enable)
+{
+	u32 reg_val;
+
+	reg_val = elm_read_reg(info, ELM_PAGE_CTRL);
+	if (enable)
+		reg_val |= BIT(index);	/* enable page mode */
+	else
+		reg_val &= ~BIT(index);	/* disable page mode */
+
+	elm_write_reg(info, ELM_PAGE_CTRL, reg_val);
+}
+
+/**
+ * elm_load_syndrome - Load ELM syndrome reg
+ * @info:	elm info
+ * @err_vec:	elm error vectors
+ * @ecc:	buffer with calculated ecc
+ *
+ * Load syndrome fragment registers with calculated ecc in reverse order.
+ */
+static void elm_load_syndrome(struct elm_info *info,
+		struct elm_errorvec *err_vec, u8 *ecc)
+{
+	int i, offset;
+	u32 val;
+
+	for (i = 0; i < info->ecc_steps; i++) {
+
+		/* Check error reported */
+		if (err_vec[i].error_reported) {
+			elm_configure_page_mode(info, i, true);
+			offset = ELM_SYNDROME_FRAGMENT_0 +
+				SYNDROME_FRAGMENT_REG_SIZE * i;
+			switch (info->bch_type) {
+			case BCH8_ECC:
+				/* syndrome fragment 0 = ecc[9-12B] */
+				val = cpu_to_be32(*(u32 *) &ecc[9]);
+				elm_write_reg(info, offset, val);
+
+				/* syndrome fragment 1 = ecc[5-8B] */
+				offset += 4;
+				val = cpu_to_be32(*(u32 *) &ecc[5]);
+				elm_write_reg(info, offset, val);
+
+				/* syndrome fragment 2 = ecc[1-4B] */
+				offset += 4;
+				val = cpu_to_be32(*(u32 *) &ecc[1]);
+				elm_write_reg(info, offset, val);
+
+				/* syndrome fragment 3 = ecc[0B] */
+				offset += 4;
+				val = ecc[0];
+				elm_write_reg(info, offset, val);
+				break;
+			case BCH4_ECC:
+				/* syndrome fragment 0 = ecc[20-52b] bits */
+				val = (cpu_to_be32(*(u32 *) &ecc[3]) >> 4) |
+					((ecc[2] & 0xf) << 28);
+				elm_write_reg(info, offset, val);
+
+				/* syndrome fragment 1 = ecc[0-20b] bits */
+				offset += 4;
+				val = cpu_to_be32(*(u32 *) &ecc[0]) >> 12;
+				elm_write_reg(info, offset, val);
+				break;
+			case BCH16_ECC:
+				val = cpu_to_be32(*(u32 *) &ecc[22]);
+				elm_write_reg(info, offset, val);
+				offset += 4;
+				val = cpu_to_be32(*(u32 *) &ecc[18]);
+				elm_write_reg(info, offset, val);
+				offset += 4;
+				val = cpu_to_be32(*(u32 *) &ecc[14]);
+				elm_write_reg(info, offset, val);
+				offset += 4;
+				val = cpu_to_be32(*(u32 *) &ecc[10]);
+				elm_write_reg(info, offset, val);
+				offset += 4;
+				val = cpu_to_be32(*(u32 *) &ecc[6]);
+				elm_write_reg(info, offset, val);
+				offset += 4;
+				val = cpu_to_be32(*(u32 *) &ecc[2]);
+				elm_write_reg(info, offset, val);
+				offset += 4;
+				val = cpu_to_be32(*(u32 *) &ecc[0]) >> 16;
+				elm_write_reg(info, offset, val);
+				break;
+			default:
+				pr_err("invalid config bch_type\n");
+			}
+		}
+
+		/* Update ecc pointer with ecc byte size */
+		ecc += info->ecc_syndrome_size;
+	}
+}
+
+/**
+ * elm_start_processing - start elm syndrome processing
+ * @info:	elm info
+ * @err_vec:	elm error vectors
+ *
+ * Set syndrome valid bit for syndrome fragment registers for which
+ * elm syndrome fragment registers are loaded. This enables elm module
+ * to start processing syndrome vectors.
+ */
+static void elm_start_processing(struct elm_info *info,
+		struct elm_errorvec *err_vec)
+{
+	int i, offset;
+	u32 reg_val;
+
+	/*
+	 * Set syndrome vector valid, so that ELM module
+	 * will process it for vectors error is reported
+	 */
+	for (i = 0; i < info->ecc_steps; i++) {
+		if (err_vec[i].error_reported) {
+			offset = ELM_SYNDROME_FRAGMENT_6 +
+				SYNDROME_FRAGMENT_REG_SIZE * i;
+			reg_val = elm_read_reg(info, offset);
+			reg_val |= ELM_SYNDROME_VALID;
+			elm_write_reg(info, offset, reg_val);
+		}
+	}
+}
+
+/**
+ * elm_error_correction - locate correctable error position
+ * @info:	elm info
+ * @err_vec:	elm error vectors
+ *
+ * On completion of processing by elm module, error location status
+ * register updated with correctable/uncorrectable error information.
+ * In case of correctable errors, number of errors located from
+ * elm location status register & read the positions from
+ * elm error location register.
+ */
+static void elm_error_correction(struct elm_info *info,
+		struct elm_errorvec *err_vec)
+{
+	int i, j, errors = 0;
+	int offset;
+	u32 reg_val;
+
+	for (i = 0; i < info->ecc_steps; i++) {
+
+		/* Check error reported */
+		if (err_vec[i].error_reported) {
+			offset = ELM_LOCATION_STATUS + ERROR_LOCATION_SIZE * i;
+			reg_val = elm_read_reg(info, offset);
+
+			/* Check correctable error or not */
+			if (reg_val & ECC_CORRECTABLE_MASK) {
+				offset = ELM_ERROR_LOCATION_0 +
+					ERROR_LOCATION_SIZE * i;
+
+				/* Read count of correctable errors */
+				err_vec[i].error_count = reg_val &
+					ECC_NB_ERRORS_MASK;
+
+				/* Update the error locations in error vector */
+				for (j = 0; j < err_vec[i].error_count; j++) {
+
+					reg_val = elm_read_reg(info, offset);
+					err_vec[i].error_loc[j] = reg_val &
+						ECC_ERROR_LOCATION_MASK;
+
+					/* Update error location register */
+					offset += 4;
+				}
+
+				errors += err_vec[i].error_count;
+			} else {
+				err_vec[i].error_uncorrectable = true;
+			}
+
+			/* Clearing interrupts for processed error vectors */
+			elm_write_reg(info, ELM_IRQSTATUS, BIT(i));
+
+			/* Disable page mode */
+			elm_configure_page_mode(info, i, false);
+		}
+	}
+}
+
+static int elm_poll(struct elm_info *info)
+{
+	u32 reg_val;
+
+	reg_val = elm_read_reg(info, ELM_IRQSTATUS);
+
+	/* All error vectors processed */
+	if (reg_val & INTR_STATUS_PAGE_VALID) {
+		elm_write_reg(info, ELM_IRQSTATUS,
+				reg_val & INTR_STATUS_PAGE_VALID);
+		return 0;
+	}
+
+	return -EINPROGRESS;
+}
+
+/**
+ * elm_decode_bch_error_page - Locate error position
+ * @dev:	device pointer
+ * @ecc_calc:	calculated ECC bytes from GPMC
+ * @err_vec:	elm error vectors
+ *
+ * Called with one or more error reported vectors & vectors with
+ * error reported is updated in err_vec[].error_reported
+ */
+int elm_decode_bch_error_page(u8 *ecc_calc, struct elm_errorvec *err_vec)
+{
+	struct elm_info *info = ginfo;
+	u32 reg_val;
+	uint64_t start;
+
+	if (!info)
+		return -ENODEV;
+
+	/* Enable page mode interrupt */
+	reg_val = elm_read_reg(info, ELM_IRQSTATUS);
+	elm_write_reg(info, ELM_IRQSTATUS, reg_val & INTR_STATUS_PAGE_VALID);
+	elm_write_reg(info, ELM_IRQENABLE, INTR_EN_PAGE_MASK);
+
+	/* Load valid ecc byte to syndrome fragment register */
+	elm_load_syndrome(info, err_vec, ecc_calc);
+
+	/* Enable syndrome processing for which syndrome fragment is updated */
+	elm_start_processing(info, err_vec);
+
+	/* Wait for ELM module to finish locating error correction */
+	start = get_time_ns();
+	while (elm_poll(info) < 0) {
+		if (is_timeout(start, SECOND))
+			return -ETIMEDOUT;
+	}
+
+	/* Disable page mode interrupt */
+	reg_val = elm_read_reg(info, ELM_IRQENABLE);
+	elm_write_reg(info, ELM_IRQENABLE, reg_val & ~INTR_EN_PAGE_MASK);
+	elm_error_correction(info, err_vec);
+
+	return 0;
+}
+
+static int elm_probe(struct device_d *dev)
+{
+	struct resource *res;
+	struct elm_info *info;
+
+	info = xzalloc(sizeof(*info));
+
+	info->dev = dev;
+
+	res = dev_request_mem_resource(dev, 0);
+	if (IS_ERR(res))
+		return PTR_ERR(res);
+	info->elm_base = IOMEM(res->start);
+
+	dev->priv = info;
+
+	ginfo = info;
+
+	return 0;
+}
+
+static struct of_device_id elm_compatible[] = {
+	{
+		.compatible = "ti,am3352-elm",
+	}, {
+		/* sentinel */
+	}
+};
+
+static struct driver_d omap_elm_driver = {
+	.name = "omap-elm",
+	.probe = elm_probe,
+	.of_compatible = DRV_OF_COMPAT(elm_compatible)
+};
+coredevice_platform_driver(omap_elm_driver);
diff --git a/include/platform_data/elm.h b/include/platform_data/elm.h
new file mode 100644
index 0000000000..bc5d2edb1d
--- /dev/null
+++ b/include/platform_data/elm.h
@@ -0,0 +1,53 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * BCH Error Location Module
+ *
+ * Copyright (C) 2012 Texas Instruments Incorporated - http://www.ti.com/
+ */
+
+#ifndef __ELM_H
+#define __ELM_H
+
+enum bch_ecc {
+	BCH4_ECC = 0,
+	BCH8_ECC,
+	BCH16_ECC,
+};
+
+/* ELM support 8 error syndrome process */
+#define ERROR_VECTOR_MAX		8
+
+/**
+ * struct elm_errorvec - error vector for elm
+ * @error_reported:		set true for vectors error is reported
+ * @error_uncorrectable:	number of uncorrectable errors
+ * @error_count:		number of correctable errors in the sector
+ * @error_loc:			buffer for error location
+ *
+ */
+struct elm_errorvec {
+	bool error_reported;
+	bool error_uncorrectable;
+	int error_count;
+	int error_loc[16];
+};
+
+#if IS_ENABLED(CONFIG_MTD_NAND_OMAP_ELM)
+int elm_decode_bch_error_page(u8 *ecc_calc, struct elm_errorvec *err_vec);
+int elm_config(enum bch_ecc bch_type, int ecc_steps, int ecc_step_size,
+	       int ecc_syndrome_size);
+#else
+static inline int
+elm_decode_bch_error_page(u8 *ecc_calc, struct elm_errorvec *err_vec)
+{
+	return -ENODEV;
+}
+
+static inline int elm_config(enum bch_ecc bch_type, int ecc_steps,
+			     int ecc_step_size, int ecc_syndrome_size)
+{
+	return -ENOSYS;
+}
+#endif /* CONFIG_MTD_NAND_OMAP_ELM */
+
+#endif /* __ELM_H */
-- 
2.23.0


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