ath79: add NAND driver for MikroTik RB91xG series

Main part is copied from ar71xx original driver rb91x_nand
written by Gabor Juhos <juhosg@openwrt.org>.

What is done:
* Support of kernel 5.4 and 5.10,
* DTS support,
* New gpio API (gpiod_*) support.

Reviewed-by: Sergey Ryazanov <ryazanov.s.a@gmail.com>
Signed-off-by: Denis Kalashnikov <denis281089@gmail.com>
(cherry-picked from commit 820e660cd7463aa6d5ed9d31baf0f3c35596ce57)

3 files changed, 397 insertions, 0 deletions

diff --git a/target/linux/ath79/files/drivers/mtd/nand/raw/rb91x_nand.c b/target/linux/ath79/files/drivers/mtd/nand/raw/rb91x_nand.c
new file mode 100644
index 0000000000..e231944519
--- /dev/null
+++ b/target/linux/ath79/files/drivers/mtd/nand/raw/rb91x_nand.c
@@ -0,0 +1,375 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *  MikroTik RB91x NAND flash driver
+ *
+ *  Main part is copied from original driver written by Gabor Juhos.
+ *
+ *  Copyright (C) 2013-2014 Gabor Juhos <juhosg@openwrt.org>
+ */
+
+/*
+ * WARNING: to speed up NAND reading/writing we are working with SoC GPIO
+ * controller registers directly -- not through standard GPIO API.
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/mtd/rawnand.h>
+#include <linux/mtd/mtd.h>
+#include <linux/mtd/partitions.h>
+#include <linux/platform_device.h>
+#include <linux/gpio/consumer.h>
+#include <linux/version.h>
+#include <linux/of_platform.h>
+
+#include <asm/mach-ath79/ar71xx_regs.h>
+
+/* Bit masks for NAND data lines in ath79 gpio 32-bit register */
+#define RB91X_NAND_NRW_BIT BIT(12)
+#define RB91X_NAND_DATA_BITS (BIT(0) | BIT(1) | BIT(2) | BIT(3) | BIT(4) \
+			    | BIT(13) | BIT(14) | BIT(15))
+#define RB91X_NAND_LOW_DATA_MASK	0x1f
+#define RB91X_NAND_HIGH_DATA_MASK	0xe0
+#define RB91X_NAND_HIGH_DATA_SHIFT	8
+
+enum rb91x_nand_gpios {
+	RB91X_NAND_READ,/* Read */
+	RB91X_NAND_RDY, /* NAND Ready */
+	RB91X_NAND_NCE, /* Chip Enable. Active low */
+	RB91X_NAND_CLE, /* Command Latch Enable */
+	RB91X_NAND_ALE, /* Address Latch Enable */
+	RB91X_NAND_NRW, /* Read/Write. Active low */
+	RB91X_NAND_NLE, /* Latch Enable. Active low */
+
+	RB91X_NAND_GPIOS,
+};
+
+struct rb91x_nand_drvdata {
+	struct nand_chip chip;
+	struct device *dev;
+	struct gpio_desc **gpio;
+	void __iomem *ath79_gpio_base;
+};
+
+static inline void rb91x_nand_latch_lock(struct rb91x_nand_drvdata *drvdata,
+					 int lock)
+{
+	gpiod_set_value_cansleep(drvdata->gpio[RB91X_NAND_NLE], lock);
+}
+
+static int rb91x_ooblayout_ecc(struct mtd_info *mtd, int section,
+			       struct mtd_oob_region *oobregion)
+{
+	switch (section) {
+	case 0:
+		oobregion->offset = 8;
+		oobregion->length = 3;
+		return 0;
+	case 1:
+		oobregion->offset = 13;
+		oobregion->length = 3;
+		return 0;
+	default:
+		return -ERANGE;
+	}
+}
+
+static int rb91x_ooblayout_free(struct mtd_info *mtd, int section,
+				struct mtd_oob_region *oobregion)
+{
+	switch (section) {
+	case 0:
+		oobregion->offset = 0;
+		oobregion->length = 4;
+		return 0;
+	case 1:
+		oobregion->offset = 4;
+		oobregion->length = 1;
+		return 0;
+	case 2:
+		oobregion->offset = 6;
+		oobregion->length = 2;
+		return 0;
+	case 3:
+		oobregion->offset = 11;
+		oobregion->length = 2;
+		return 0;
+	default:
+		return -ERANGE;
+	}
+}
+
+static const struct mtd_ooblayout_ops rb91x_nand_ecclayout_ops = {
+	.ecc = rb91x_ooblayout_ecc,
+	.free = rb91x_ooblayout_free,
+};
+
+static void rb91x_nand_write(struct rb91x_nand_drvdata *drvdata,
+			     const u8 *buf,
+			     unsigned len)
+{
+	void __iomem *base = drvdata->ath79_gpio_base;
+	u32 oe_reg;
+	u32 out_reg;
+	u32 out;
+	unsigned i;
+
+	rb91x_nand_latch_lock(drvdata, 1);
+
+	oe_reg = __raw_readl(base + AR71XX_GPIO_REG_OE);
+	out_reg = __raw_readl(base + AR71XX_GPIO_REG_OUT);
+
+	/* Set data lines to output mode */
+	__raw_writel(oe_reg & ~(RB91X_NAND_DATA_BITS | RB91X_NAND_NRW_BIT),
+		     base + AR71XX_GPIO_REG_OE);
+
+	out = out_reg & ~(RB91X_NAND_DATA_BITS | RB91X_NAND_NRW_BIT);
+	for (i = 0; i != len; i++) {
+		u32 data;
+
+		data = (buf[i] & RB91X_NAND_HIGH_DATA_MASK) <<
+			RB91X_NAND_HIGH_DATA_SHIFT;
+		data |= buf[i] & RB91X_NAND_LOW_DATA_MASK;
+		data |= out;
+		__raw_writel(data, base + AR71XX_GPIO_REG_OUT);
+
+		/* Deactivate WE line */
+		data |= RB91X_NAND_NRW_BIT;
+		__raw_writel(data, base + AR71XX_GPIO_REG_OUT);
+		/* Flush write */
+		__raw_readl(base + AR71XX_GPIO_REG_OUT);
+	}
+
+	/* Restore registers */
+	__raw_writel(out_reg, base + AR71XX_GPIO_REG_OUT);
+	__raw_writel(oe_reg, base + AR71XX_GPIO_REG_OE);
+	/* Flush write */
+	__raw_readl(base + AR71XX_GPIO_REG_OUT);
+
+	rb91x_nand_latch_lock(drvdata, 0);
+}
+
+static void rb91x_nand_read(struct rb91x_nand_drvdata *drvdata,
+			    u8 *read_buf,
+			    unsigned len)
+{
+	void __iomem *base = drvdata->ath79_gpio_base;
+	u32 oe_reg;
+	u32 out_reg;
+	unsigned i;
+
+	/* Enable read mode */
+	gpiod_set_value_cansleep(drvdata->gpio[RB91X_NAND_READ], 1);
+
+	rb91x_nand_latch_lock(drvdata, 1);
+
+	/* Save registers */
+	oe_reg = __raw_readl(base + AR71XX_GPIO_REG_OE);
+	out_reg = __raw_readl(base + AR71XX_GPIO_REG_OUT);
+
+	/* Set data lines to input mode */
+	__raw_writel(oe_reg | RB91X_NAND_DATA_BITS,
+		     base + AR71XX_GPIO_REG_OE);
+
+	for (i = 0; i < len; i++) {
+		u32 in;
+		u8 data;
+
+		/* Activate RE line */
+		__raw_writel(RB91X_NAND_NRW_BIT, base + AR71XX_GPIO_REG_CLEAR);
+		/* Flush write */
+		__raw_readl(base + AR71XX_GPIO_REG_CLEAR);
+
+		/* Read input lines */
+		in = __raw_readl(base + AR71XX_GPIO_REG_IN);
+
+		/* Deactivate RE line */
+		__raw_writel(RB91X_NAND_NRW_BIT, base + AR71XX_GPIO_REG_SET);
+
+		data = (in & RB91X_NAND_LOW_DATA_MASK);
+		data |= (in >> RB91X_NAND_HIGH_DATA_SHIFT) &
+			RB91X_NAND_HIGH_DATA_MASK;
+
+		read_buf[i] = data;
+	}
+
+	/* Restore  registers */
+	__raw_writel(out_reg, base + AR71XX_GPIO_REG_OUT);
+	__raw_writel(oe_reg, base + AR71XX_GPIO_REG_OE);
+	/* Flush write */
+	__raw_readl(base + AR71XX_GPIO_REG_OUT);
+
+	rb91x_nand_latch_lock(drvdata, 0);
+
+	/* Disable read mode */
+	gpiod_set_value_cansleep(drvdata->gpio[RB91X_NAND_READ], 0);
+}
+
+static int rb91x_nand_dev_ready(struct nand_chip *chip)
+{
+	struct rb91x_nand_drvdata *drvdata = (struct rb91x_nand_drvdata *)(chip->priv);
+
+	return gpiod_get_value_cansleep(drvdata->gpio[RB91X_NAND_RDY]);
+}
+
+static void rb91x_nand_cmd_ctrl(struct nand_chip *chip, int cmd,
+				unsigned int ctrl)
+{
+	struct rb91x_nand_drvdata *drvdata = chip->priv;
+
+	if (ctrl & NAND_CTRL_CHANGE) {
+		gpiod_set_value_cansleep(drvdata->gpio[RB91X_NAND_CLE],
+					(ctrl & NAND_CLE) ? 1 : 0);
+		gpiod_set_value_cansleep(drvdata->gpio[RB91X_NAND_ALE],
+					(ctrl & NAND_ALE) ? 1 : 0);
+		gpiod_set_value_cansleep(drvdata->gpio[RB91X_NAND_NCE],
+					(ctrl & NAND_NCE) ? 1 : 0);
+	}
+
+	if (cmd != NAND_CMD_NONE) {
+		u8 t = cmd;
+
+		rb91x_nand_write(drvdata, &t, 1);
+	}
+}
+
+static u8 rb91x_nand_read_byte(struct nand_chip *chip)
+{
+	u8 data = 0xff;
+
+	rb91x_nand_read(chip->priv, &data, 1);
+
+	return data;
+}
+
+static void rb91x_nand_read_buf(struct nand_chip *chip, u8 *buf, int len)
+{
+	rb91x_nand_read(chip->priv, buf, len);
+}
+
+static void rb91x_nand_write_buf(struct nand_chip *chip, const u8 *buf, int len)
+{
+	rb91x_nand_write(chip->priv, buf, len);
+}
+
+static void rb91x_nand_release(struct rb91x_nand_drvdata *drvdata)
+{
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(5,8,0)
+	mtd_device_unregister(nand_to_mtd(&drvdata->chip));
+	nand_cleanup(&drvdata->chip);
+#else
+	nand_release(&drvdata->chip);
+#endif
+}
+
+static int rb91x_nand_probe(struct platform_device *pdev)
+{
+	struct rb91x_nand_drvdata *drvdata;
+	struct mtd_info *mtd;
+	int r;
+	struct device *dev = &pdev->dev;
+	struct gpio_descs *gpios;
+
+	drvdata = devm_kzalloc(dev, sizeof(*drvdata), GFP_KERNEL);
+	if (!drvdata)
+		return -ENOMEM;
+
+	platform_set_drvdata(pdev, drvdata);
+
+	gpios = gpiod_get_array(dev, NULL, GPIOD_OUT_LOW);
+	if (IS_ERR(gpios)) {
+		dev_err(dev, "failed to get gpios: %d\n", (int)gpios);
+		return -EINVAL;
+	}
+
+	if (gpios->ndescs != RB91X_NAND_GPIOS) {
+		dev_err(dev, "expected %d gpios\n", RB91X_NAND_GPIOS);
+		return -EINVAL;
+	}
+
+	drvdata->gpio = gpios->desc;
+
+	gpiod_direction_input(drvdata->gpio[RB91X_NAND_RDY]);
+
+	drvdata->ath79_gpio_base = ioremap(AR71XX_GPIO_BASE, AR71XX_GPIO_SIZE);
+
+	drvdata->dev = dev;
+
+	drvdata->chip.priv = drvdata;
+
+	drvdata->chip.legacy.cmd_ctrl = rb91x_nand_cmd_ctrl;
+	drvdata->chip.legacy.dev_ready = rb91x_nand_dev_ready;
+	drvdata->chip.legacy.read_byte = rb91x_nand_read_byte;
+	drvdata->chip.legacy.write_buf = rb91x_nand_write_buf;
+	drvdata->chip.legacy.read_buf = rb91x_nand_read_buf;
+
+	drvdata->chip.legacy.chip_delay = 25;
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(5,9,0)
+	drvdata->chip.ecc.engine_type      = NAND_ECC_ENGINE_TYPE_SOFT;
+	drvdata->chip.ecc.algo             = NAND_ECC_ALGO_HAMMING;
+#else
+	drvdata->chip.ecc.mode             = NAND_ECC_SOFT;
+	drvdata->chip.ecc.algo             = NAND_ECC_HAMMING;
+#endif
+	drvdata->chip.options = NAND_NO_SUBPAGE_WRITE;
+
+	r = nand_scan(&drvdata->chip, 1);
+	if (r) {
+		dev_err(dev, "nand_scan() failed: %d\n", r);
+		return r;
+	}
+
+	mtd = nand_to_mtd(&drvdata->chip);
+	mtd->dev.parent = dev;
+	mtd_set_of_node(mtd, dev->of_node);
+	mtd->owner = THIS_MODULE;
+	if (mtd->writesize == 512)
+		mtd_set_ooblayout(mtd, &rb91x_nand_ecclayout_ops);
+
+	r = mtd_device_register(mtd, NULL, 0);
+	if (r) {
+		dev_err(dev, "mtd_device_register() failed: %d\n",
+			r);
+		goto err_release_nand;
+	}
+
+	return 0;
+
+err_release_nand:
+	rb91x_nand_release(drvdata);
+	return r;
+}
+
+static int rb91x_nand_remove(struct platform_device *pdev)
+{
+	struct rb91x_nand_drvdata *drvdata = platform_get_drvdata(pdev);
+
+	rb91x_nand_release(drvdata);
+
+	return 0;
+}
+
+static const struct of_device_id rb91x_nand_match[] = {
+	{ .compatible = "mikrotik,rb91x-nand" },
+	{},
+};
+
+MODULE_DEVICE_TABLE(of, rb91x_nand_match);
+
+static struct platform_driver rb91x_nand_driver = {
+	.probe	= rb91x_nand_probe,
+	.remove	= rb91x_nand_remove,
+	.driver	= {
+		.name	= "rb91x-nand",
+		.owner	= THIS_MODULE,
+		.of_match_table = rb91x_nand_match,
+	},
+};
+
+module_platform_driver(rb91x_nand_driver);
+
+MODULE_DESCRIPTION("MikrotTik RB91x NAND flash driver");
+MODULE_VERSION(DRV_VERSION);
+MODULE_AUTHOR("Gabor Juhos <juhosg@openwrt.org>");
+MODULE_AUTHOR("Denis Kalashnikov <denis281089@gmail.com>");
+MODULE_LICENSE("GPL v2");
diff --git a/target/linux/ath79/mikrotik/config-default b/target/linux/ath79/mikrotik/config-default
index 8609893f6e..97dddfb197 100644
--- a/target/linux/ath79/mikrotik/config-default
+++ b/target/linux/ath79/mikrotik/config-default
@@ -15,6 +15,7 @@ CONFIG_MTD_NAND_AR934X=y
 CONFIG_MTD_NAND_CORE=y
 CONFIG_MTD_NAND_ECC=y
 CONFIG_MTD_NAND_RB4XX=y
+CONFIG_MTD_NAND_RB91X=y
 CONFIG_MTD_RAW_NAND=y
 CONFIG_MTD_ROUTERBOOT_PARTS=y
 CONFIG_MTD_SPI_NAND=y
diff --git a/target/linux/ath79/patches-5.4/939-mikrotik-rb91x.patch b/target/linux/ath79/patches-5.4/939-mikrotik-rb91x.patch
index baeaab4611..6d84443945 100644
--- a/target/linux/ath79/patches-5.4/939-mikrotik-rb91x.patch
+++ b/target/linux/ath79/patches-5.4/939-mikrotik-rb91x.patch
@@ -1,3 +1,24 @@
+--- a/drivers/mtd/nand/raw/Kconfig
++++ b/drivers/mtd/nand/raw/Kconfig
+@@ -559,4 +559,8 @@ config MTD_NAND_RB4XX
+ 	  Enables support for the NAND flash chip on Mikrotik Routerboard
+ 	  RB4xx series.
+ 
++config MTD_NAND_RB91X
++	tristate "MikroTik RB91x NAND driver support"
++	depends on ATH79 && MTD_RAW_NAND
++
+ endif # MTD_RAW_NAND
+--- a/drivers/mtd/nand/raw/Makefile
++++ b/drivers/mtd/nand/raw/Makefile
+@@ -59,6 +59,7 @@ obj-$(CONFIG_MTD_NAND_STM32_FMC2)	+= stm
+ obj-$(CONFIG_MTD_NAND_MESON)		+= meson_nand.o
+ obj-$(CONFIG_MTD_NAND_AR934X)		+= ar934x_nand.o
+ obj-$(CONFIG_MTD_NAND_RB4XX)		+= nand_rb4xx.o
++obj-$(CONFIG_MTD_NAND_RB91X)		+= rb91x_nand.o
+ 
+ nand-objs := nand_base.o nand_legacy.o nand_bbt.o nand_timings.o nand_ids.o
+ nand-objs += nand_onfi.o
 --- a/drivers/gpio/Kconfig
 +++ b/drivers/gpio/Kconfig
 @@ -130,6 +130,10 @@ config GPIO_ATH79