mtd: devices: elm: Add support for ELM error correction

The ELM hardware module can be used to speedup BCH 4/8/16 ECC scheme
error correction.
For now only 4 & 8 bit support is added
Signed-off-by: Philip Avinash <avinashphilip@ti.com>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>

Documentation/devicetree/bindings/mtd/elm.txt

+Error location module
+
+Required properties:
+- compatible: Must be "ti,am33xx-elm"
+- reg: physical base address and size of the registers map.
+- interrupts: Interrupt number for the elm.
+
+Optional properties:
+- ti,hwmods: Name of the hwmod associated to the elm
+
+Example:
+elm: elm@0 {
+	compatible	= "ti,am33xx-elm";
+	reg = <0x48080000 0x2000>;
+	interrupts = <4>;
+};

drivers/mtd/devices/Makefile

@@ -17,8 +17,10 @@ obj-$(CONFIG_MTD_LART)		+= lart.o
 obj-$(CONFIG_MTD_BLOCK2MTD)	+= block2mtd.o
 obj-$(CONFIG_MTD_DATAFLASH)	+= mtd_dataflash.o
 obj-$(CONFIG_MTD_M25P80)	+= m25p80.o
+obj-$(CONFIG_MTD_NAND_OMAP_BCH)	+= elm.o
 obj-$(CONFIG_MTD_SPEAR_SMI)	+= spear_smi.o
 obj-$(CONFIG_MTD_SST25L)	+= sst25l.o
 obj-$(CONFIG_MTD_BCM47XXSFLASH)	+= bcm47xxsflash.o
 
-CFLAGS_docg3.o			+= -I$(src)
+
\ No newline at end of file
+CFLAGS_docg3.o			+= -I$(src)

drivers/mtd/devices/elm.c

+/*
+ * Error Location Module
+ *
+ * Copyright (C) 2012 Texas Instruments Incorporated - http://www.ti.com/
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ */
+
+#include <linux/platform_device.h>
+#include <linux/module.h>
+#include <linux/interrupt.h>
+#include <linux/io.h>
+#include <linux/of.h>
+#include <linux/pm_runtime.h>
+#include <linux/platform_data/elm.h>
+
+#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_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_info {
+	struct device *dev;
+	void __iomem *elm_base;
+	struct completion elm_completion;
+	struct list_head list;
+	enum bch_ecc bch_type;
+};
+
+static LIST_HEAD(elm_devices);
+
+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
+ */
+void elm_config(struct device *dev, enum bch_ecc bch_type)
+{
+	u32 reg_val;
+	struct elm_info *info = dev_get_drvdata(dev);
+
+	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;
+}
+EXPORT_SYMBOL(elm_config);
+
+/**
+ * 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 < ERROR_VECTOR_MAX; 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;
+
+			/* BCH8 */
+			if (info->bch_type) {
+
+				/* 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);
+			} else {
+				/* 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);
+			}
+		}
+
+		/* Update ecc pointer with ecc byte size */
+		ecc += info->bch_type ? BCH8_SIZE : BCH4_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 < ERROR_VECTOR_MAX; 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 < ERROR_VECTOR_MAX; 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);
+		}
+	}
+}
+
+/**
+ * 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
+ */
+void elm_decode_bch_error_page(struct device *dev, u8 *ecc_calc,
+		struct elm_errorvec *err_vec)
+{
+	struct elm_info *info = dev_get_drvdata(dev);
+	u32 reg_val;
+
+	/* 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 */
+	wait_for_completion(&info->elm_completion);
+
+	/* 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);
+}
+EXPORT_SYMBOL(elm_decode_bch_error_page);
+
+static irqreturn_t elm_isr(int this_irq, void *dev_id)
+{
+	u32 reg_val;
+	struct elm_info *info = dev_id;
+
+	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);
+		complete(&info->elm_completion);
+		return IRQ_HANDLED;
+	}
+
+	return IRQ_NONE;
+}
+
+static int elm_probe(struct platform_device *pdev)
+{
+	int ret = 0;
+	struct resource *res, *irq;
+	struct elm_info *info;
+
+	info = devm_kzalloc(&pdev->dev, sizeof(*info), GFP_KERNEL);
+	if (!info) {
+		dev_err(&pdev->dev, "failed to allocate memory\n");
+		return -ENOMEM;
+	}
+
+	info->dev = &pdev->dev;
+
+	irq = platform_get_resource(pdev, IORESOURCE_IRQ, 0);
+	if (!irq) {
+		dev_err(&pdev->dev, "no irq resource defined\n");
+		return -ENODEV;
+	}
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	if (!res) {
+		dev_err(&pdev->dev, "no memory resource defined\n");
+		return -ENODEV;
+	}
+
+	info->elm_base = devm_request_and_ioremap(&pdev->dev, res);
+	if (!info->elm_base)
+		return -EADDRNOTAVAIL;
+
+	ret = devm_request_irq(&pdev->dev, irq->start, elm_isr, 0,
+			pdev->name, info);
+	if (ret) {
+		dev_err(&pdev->dev, "failure requesting irq %i\n", irq->start);
+		return ret;
+	}
+
+	pm_runtime_enable(&pdev->dev);
+	if (pm_runtime_get_sync(&pdev->dev)) {
+		ret = -EINVAL;
+		pm_runtime_disable(&pdev->dev);
+		dev_err(&pdev->dev, "can't enable clock\n");
+		return ret;
+	}
+
+	init_completion(&info->elm_completion);
+	INIT_LIST_HEAD(&info->list);
+	list_add(&info->list, &elm_devices);
+	platform_set_drvdata(pdev, info);
+	return ret;
+}
+
+static int elm_remove(struct platform_device *pdev)
+{
+	pm_runtime_put_sync(&pdev->dev);
+	pm_runtime_disable(&pdev->dev);
+	platform_set_drvdata(pdev, NULL);
+	return 0;
+}
+
+#ifdef CONFIG_OF
+static const struct of_device_id elm_of_match[] = {
+	{ .compatible = "ti,am33xx-elm" },
+	{},
+};
+MODULE_DEVICE_TABLE(of, elm_of_match);
+#endif
+
+static struct platform_driver elm_driver = {
+	.driver	= {
+		.name	= "elm",
+		.owner	= THIS_MODULE,
+		.of_match_table = of_match_ptr(elm_of_match),
+	},
+	.probe	= elm_probe,
+	.remove	= elm_remove,
+};
+
+module_platform_driver(elm_driver);
+
+MODULE_DESCRIPTION("ELM driver for BCH error correction");
+MODULE_AUTHOR("Texas Instruments");
+MODULE_ALIAS("platform: elm");
+MODULE_LICENSE("GPL v2");

include/linux/platform_data/elm.h

+/*
+ * BCH Error Location Module
+ *
+ * Copyright (C) 2012 Texas Instruments Incorporated - http://www.ti.com/
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ */
+
+#ifndef __ELM_H
+#define __ELM_H
+
+enum bch_ecc {
+	BCH4_ECC = 0,
+	BCH8_ECC,
+};
+
+/* ELM support 8 error syndrome process */
+#define ERROR_VECTOR_MAX		8
+
+#define BCH8_ECC_OOB_BYTES		13
+#define BCH4_ECC_OOB_BYTES		7
+/* RBL requires 14 byte even though BCH8 uses only 13 byte */
+#define BCH8_SIZE			(BCH8_ECC_OOB_BYTES + 1)
+#define BCH4_SIZE			(BCH4_ECC_OOB_BYTES)
+
+/**
+ * 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[ERROR_VECTOR_MAX];
+};
+
+void elm_decode_bch_error_page(struct device *dev, u8 *ecc_calc,
+		struct elm_errorvec *err_vec);
+void elm_config(struct device *dev, enum bch_ecc bch_type);
+#endif /* __ELM_H */