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>

2 files changed, 407 insertions, 1 deletions

diff --git a/drivers/mtd/devices/Makefile b/drivers/mtd/devices/Makefile
index 395733a30ef4..369a1943ca25 100644
--- a/drivers/mtd/devices/Makefile
+++ b/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)
diff --git a/drivers/mtd/devices/elm.c b/drivers/mtd/devices/elm.c
new file mode 100644
index 000000000000..b93a349ae587
--- /dev/null
+++ b/drivers/mtd/devices/elm.c
@@ -0,0 +1,404 @@
+/*
+ * 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");