mtd: nand: Add OX820 NAND Support

Add NAND driver to support the Oxford Semiconductor OX820 NAND Controller.
This is a simple memory mapped NAND controller with single chip select and
software ECC.

Acked-by: Rob Herring <[e-mail]>
Signed-off-by: Neil Armstrong <[e-mail]>
Signed-off-by: Boris Brezillon <[e-mail]>

Documentation/devicetree/bindings/mtd/oxnas-nand.txt

···
+* Oxford Semiconductor OXNAS NAND Controller
+
+Please refer to nand.txt for generic information regarding MTD NAND bindings.
+
+Required properties:
+ - compatible: "oxsemi,ox820-nand"
+ - reg: Base address and length for NAND mapped memory.
+
+Optional Properties:
+ - clocks: phandle to the NAND gate clock if needed.
+ - resets: phandle to the NAND reset control if needed.
+
+Example:
+
+nandc: nand-controller@41000000 {
+	compatible = "oxsemi,ox820-nand";
+	reg = <0x41000000 0x100000>;
+	clocks = <&stdclk CLK_820_NAND>;
+	resets = <&reset RESET_NAND>;
+	#address-cells = <1>;
+	#size-cells = <0>;
+
+	nand@0 {
+		reg = <0>;
+		#address-cells = <1>;
+		#size-cells = <1>;
+		nand-ecc-mode = "soft";
+		nand-ecc-algo = "hamming";
+
+		partition@0 {
+			label = "boot";
+			reg = <0x00000000 0x00e00000>;
+			read-only;
+		};
+
+		partition@e00000 {
+			label = "ubi";
+			reg = <0x00e00000 0x07200000>;
+		};
+	};
+};

drivers/mtd/nand/Kconfig

···
 	  No board specific support is done by this driver, each board
 	  must advertise a platform_device for the driver to attach.
 
+config MTD_NAND_OXNAS
+	tristate "NAND Flash support for Oxford Semiconductor SoC"
+	help
+	  This enables the NAND flash controller on Oxford Semiconductor SoCs.
+
 config MTD_NAND_FSL_ELBC
 	tristate "NAND support for Freescale eLBC controllers"
 	depends on FSL_SOC

drivers/mtd/nand/Makefile

···
 obj-$(CONFIG_MTD_NAND_PLATFORM)		+= plat_nand.o
 obj-$(CONFIG_MTD_NAND_PASEMI)		+= pasemi_nand.o
 obj-$(CONFIG_MTD_NAND_ORION)		+= orion_nand.o
+obj-$(CONFIG_MTD_NAND_OXNAS)		+= oxnas_nand.o
 obj-$(CONFIG_MTD_NAND_FSL_ELBC)		+= fsl_elbc_nand.o
 obj-$(CONFIG_MTD_NAND_FSL_IFC)		+= fsl_ifc_nand.o
 obj-$(CONFIG_MTD_NAND_FSL_UPM)		+= fsl_upm.o

drivers/mtd/nand/oxnas_nand.c

···
+/*
+ * Oxford Semiconductor OXNAS NAND driver
+
+ * Copyright (C) 2016 Neil Armstrong <[e-mail]>
+ * Heavily based on plat_nand.c :
+ * Author: Vitaly Wool <[e-mail]>
+ * Copyright (C) 2013 Ma Haijun <[e-mail]>
+ * Copyright (C) 2012 John Crispin <[e-mail]>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ */
+
+#include <linux/err.h>
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+#include <linux/clk.h>
+#include <linux/reset.h>
+#include <linux/mtd/mtd.h>
+#include <linux/mtd/nand.h>
+#include <linux/mtd/partitions.h>
+#include <linux/of.h>
+
+/* Nand commands */
+#define OXNAS_NAND_CMD_ALE		BIT(18)
+#define OXNAS_NAND_CMD_CLE		BIT(19)
+
+#define OXNAS_NAND_MAX_CHIPS	1
+
+struct oxnas_nand_ctrl {
+	struct nand_hw_control base;
+	void __iomem *io_base;
+	struct clk *clk;
+	struct nand_chip *chips[OXNAS_NAND_MAX_CHIPS];
+};
+
+static uint8_t oxnas_nand_read_byte(struct mtd_info *mtd)
+{
+	struct nand_chip *chip = mtd_to_nand(mtd);
+	struct oxnas_nand_ctrl *oxnas = nand_get_controller_data(chip);
+
+	return readb(oxnas->io_base);
+}
+
+static void oxnas_nand_read_buf(struct mtd_info *mtd, u8 *buf, int len)
+{
+	struct nand_chip *chip = mtd_to_nand(mtd);
+	struct oxnas_nand_ctrl *oxnas = nand_get_controller_data(chip);
+
+	ioread8_rep(oxnas->io_base, buf, len);
+}
+
+static void oxnas_nand_write_buf(struct mtd_info *mtd, const u8 *buf, int len)
+{
+	struct nand_chip *chip = mtd_to_nand(mtd);
+	struct oxnas_nand_ctrl *oxnas = nand_get_controller_data(chip);
+
+	iowrite8_rep(oxnas->io_base, buf, len);
+}
+
+/* Single CS command control */
+static void oxnas_nand_cmd_ctrl(struct mtd_info *mtd, int cmd,
+				unsigned int ctrl)
+{
+	struct nand_chip *chip = mtd_to_nand(mtd);
+	struct oxnas_nand_ctrl *oxnas = nand_get_controller_data(chip);
+
+	if (ctrl & NAND_CLE)
+		writeb(cmd, oxnas->io_base + OXNAS_NAND_CMD_CLE);
+	else if (ctrl & NAND_ALE)
+		writeb(cmd, oxnas->io_base + OXNAS_NAND_CMD_ALE);
+}
+
+/*
+ * Probe for the NAND device.
+ */
+static int oxnas_nand_probe(struct platform_device *pdev)
+{
+	struct device_node *np = pdev->dev.of_node;
+	struct device_node *nand_np;
+	struct oxnas_nand_ctrl *oxnas;
+	struct nand_chip *chip;
+	struct mtd_info *mtd;
+	struct resource *res;
+	int nchips = 0;
+	int count = 0;
+	int err = 0;
+
+	/* Allocate memory for the device structure (and zero it) */
+	oxnas = devm_kzalloc(&pdev->dev, sizeof(struct nand_chip),
+			     GFP_KERNEL);
+	if (!oxnas)
+		return -ENOMEM;
+
+	nand_hw_control_init(&oxnas->base);
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	oxnas->io_base = devm_ioremap_resource(&pdev->dev, res);
+	if (IS_ERR(oxnas->io_base))
+		return PTR_ERR(oxnas->io_base);
+
+	oxnas->clk = devm_clk_get(&pdev->dev, NULL);
+	if (IS_ERR(oxnas->clk))
+		oxnas->clk = NULL;
+
+	/* Only a single chip node is supported */
+	count = of_get_child_count(np);
+	if (count > 1)
+		return -EINVAL;
+
+	clk_prepare_enable(oxnas->clk);
+	device_reset_optional(&pdev->dev);
+
+	for_each_child_of_node(np, nand_np) {
+		chip = devm_kzalloc(&pdev->dev, sizeof(struct nand_chip),
+				    GFP_KERNEL);
+		if (!chip)
+			return -ENOMEM;
+
+		chip->controller = &oxnas->base;
+
+		nand_set_flash_node(chip, nand_np);
+		nand_set_controller_data(chip, oxnas);
+
+		mtd = nand_to_mtd(chip);
+		mtd->dev.parent = &pdev->dev;
+		mtd->priv = chip;
+
+		chip->cmd_ctrl = oxnas_nand_cmd_ctrl;
+		chip->read_buf = oxnas_nand_read_buf;
+		chip->read_byte = oxnas_nand_read_byte;
+		chip->write_buf = oxnas_nand_write_buf;
+		chip->chip_delay = 30;
+
+		/* Scan to find existence of the device */
+		err = nand_scan(mtd, 1);
+		if (err)
+			return err;
+
+		err = mtd_device_register(mtd, NULL, 0);
+		if (err) {
+			nand_release(mtd);
+			return err;
+		}
+
+		oxnas->chips[nchips] = chip;
+		++nchips;
+	}
+
+	/* Exit if no chips found */
+	if (!nchips)
+		return -ENODEV;
+
+	platform_set_drvdata(pdev, oxnas);
+
+	return 0;
+}
+
+static int oxnas_nand_remove(struct platform_device *pdev)
+{
+	struct oxnas_nand_ctrl *oxnas = platform_get_drvdata(pdev);
+
+	if (oxnas->chips[0])
+		nand_release(nand_to_mtd(oxnas->chips[0]));
+
+	clk_disable_unprepare(oxnas->clk);
+
+	return 0;
+}
+
+static const struct of_device_id oxnas_nand_match[] = {
+	{ .compatible = "oxsemi,ox820-nand" },
+	{},
+};
+MODULE_DEVICE_TABLE(of, oxnas_nand_match);
+
+static struct platform_driver oxnas_nand_driver = {
+	.probe	= oxnas_nand_probe,
+	.remove	= oxnas_nand_remove,
+	.driver	= {
+		.name		= "oxnas_nand",
+		.of_match_table = oxnas_nand_match,
+	},
+};
+
+module_platform_driver(oxnas_nand_driver);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Neil Armstrong <[e-mail]>");
+MODULE_DESCRIPTION("Oxnas NAND driver");
+MODULE_ALIAS("platform:oxnas_nand");