Message-ID: <20150921220806.GB31505@google.com>
Date:	Mon, 21 Sep 2015 15:08:06 -0700
From:	Brian Norris <computersforpeace@...il.com>
To:	Alex Smith <alex.smith@...tec.com>
Cc:	linux-mtd@...ts.infradead.org, Alex Smith <alex@...x-smith.me.uk>,
	Zubair Lutfullah Kakakhel <Zubair.Kakakhel@...tec.com>,
	David Woodhouse <dwmw2@...radead.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 3/4] mtd: nand: jz4780: driver for NAND devices on
 JZ4780 SoCs

On Tue, Sep 08, 2015 at 10:10:52AM +0100, Alex Smith wrote:
> Add a driver for NAND devices connected to the NEMC on JZ4780 SoCs, as
> well as the hardware BCH controller. DMA is not currently implemented.
> 
> While older 47xx SoCs also have a BCH controller, they are incompatible
> with the one in the 4780 due to differing register/bit positions, which
> would make implementing a common driver for them quite messy.
> 
> Signed-off-by: Alex Smith <alex.smith@...tec.com>
> Cc: Zubair Lutfullah Kakakhel <Zubair.Kakakhel@...tec.com>
> Cc: David Woodhouse <dwmw2@...radead.org>
> Cc: Brian Norris <computersforpeace@...il.com>
> Cc: linux-mtd@...ts.infradead.org
> Cc: linux-kernel@...r.kernel.org
> ---
> v4 -> v5:
>  - Bump RB_DELAY up to be sufficient for the driver to work without a
>    busy GPIO available.
>  - Use readl_poll_timeout instead of custom polling loop.
>  - Remove useless printks.
>  - Change a BUG_ON to WARN_ON.
>  - Remove use of of_translate_address(), use standard platform resource
>    APIs.
>  - Add DRV_NAME define to avoid duplication of the same string.
> 
> v3 -> v4:
>  - Rebase to 4.2-rc4
>  - Change ECC_HW_OOB_FIRST to ECC_HW, reading OOB first is not necessary.
>  - Fix argument to get_device() in jz4780_bch_get()
> 
> v2 -> v3:
>  - Rebase to 4.0-rc6
>  - Reflect binding changes
>  - get/put_device in bch get/release
>  - Removed empty .remove() callback
>  - Removed .owner
>  - Set mtd->dev.parent
> 
> v1 -> v2:
>  - Fixed module license macro
>  - Rebase to 4.0-rc3
> ---
>  drivers/mtd/nand/Kconfig       |   7 +
>  drivers/mtd/nand/Makefile      |   1 +
>  drivers/mtd/nand/jz4780_bch.c  | 348 +++++++++++++++++++++++++++++++++++++
>  drivers/mtd/nand/jz4780_bch.h  |  42 +++++
>  drivers/mtd/nand/jz4780_nand.c | 378 +++++++++++++++++++++++++++++++++++++++++
>  5 files changed, 776 insertions(+)
>  create mode 100644 drivers/mtd/nand/jz4780_bch.c
>  create mode 100644 drivers/mtd/nand/jz4780_bch.h
>  create mode 100644 drivers/mtd/nand/jz4780_nand.c
> 
> diff --git a/drivers/mtd/nand/Kconfig b/drivers/mtd/nand/Kconfig
> index 3324281d1f53..8ffd5cd2a92b 100644
> --- a/drivers/mtd/nand/Kconfig
> +++ b/drivers/mtd/nand/Kconfig
> @@ -508,6 +508,13 @@ config MTD_NAND_JZ4740
>  	help
>  		Enables support for NAND Flash on JZ4740 SoC based boards.
>  
> +config MTD_NAND_JZ4780
> +	tristate "Support for NAND on JZ4780 SoC"
> +	depends on MACH_JZ4780 && JZ4780_NEMC

IMO, it'd be nice if this would compile test on other platforms. It'd
help make things a little closer to ready for if there is ever a
multiplatform effort for MIPS like there is for ARM. So you'd need:

	depends on JZ4780_NEMC
	depends on MACH_JZ4780 || COMPILE_TEST

or similar.

But then, you'd need to change the NEMC Kconfig to allow COMPILE_TEST
too. So it's not really worth too much to me right now. Just wanted to
throw my 2 cents out there, and you can do what you want with it.

> +	help
> +	  Enables support for NAND Flash connected to the NEMC on JZ4780 SoC
> +	  based boards, using the BCH controller for hardware error correction.
> +
>  config MTD_NAND_FSMC
>  	tristate "Support for NAND on ST Micros FSMC"
>  	depends on PLAT_SPEAR || ARCH_NOMADIK || ARCH_U8500 || MACH_U300
> diff --git a/drivers/mtd/nand/Makefile b/drivers/mtd/nand/Makefile
> index 1f897ec3c242..3ee2fd6bc641 100644
> --- a/drivers/mtd/nand/Makefile
> +++ b/drivers/mtd/nand/Makefile
> @@ -47,6 +47,7 @@ obj-$(CONFIG_MTD_NAND_NUC900)		+= nuc900_nand.o
>  obj-$(CONFIG_MTD_NAND_MPC5121_NFC)	+= mpc5121_nfc.o
>  obj-$(CONFIG_MTD_NAND_RICOH)		+= r852.o
>  obj-$(CONFIG_MTD_NAND_JZ4740)		+= jz4740_nand.o
> +obj-$(CONFIG_MTD_NAND_JZ4780)		+= jz4780_nand.o jz4780_bch.o
>  obj-$(CONFIG_MTD_NAND_GPMI_NAND)	+= gpmi-nand/
>  obj-$(CONFIG_MTD_NAND_XWAY)		+= xway_nand.o
>  obj-$(CONFIG_MTD_NAND_BCM47XXNFLASH)	+= bcm47xxnflash/
> diff --git a/drivers/mtd/nand/jz4780_bch.c b/drivers/mtd/nand/jz4780_bch.c
> new file mode 100644
> index 000000000000..6ed4ad024e83
> --- /dev/null
> +++ b/drivers/mtd/nand/jz4780_bch.c
> @@ -0,0 +1,348 @@
> +/*
> + * JZ4780 BCH controller
> + *
> + * Copyright (c) 2015 Imagination Technologies
> + * Author: Alex Smith <alex.smith@...tec.com>
> + *
> + * 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/clk.h>
> +#include <linux/delay.h>
> +#include <linux/init.h>
> +#include <linux/iopoll.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/of_platform.h>
> +#include <linux/platform_device.h>
> +#include <linux/sched.h>
> +#include <linux/slab.h>
> +
> +#include "jz4780_bch.h"
> +
> +#define BCH_BHCR			0x0
> +#define BCH_BHCCR			0x8
> +#define BCH_BHCNT			0xc
> +#define BCH_BHDR			0x10
> +#define BCH_BHPAR0			0x14
> +#define BCH_BHERR0			0x84
> +#define BCH_BHINT			0x184
> +#define BCH_BHINTES			0x188
> +#define BCH_BHINTEC			0x18c
> +#define BCH_BHINTE			0x190
> +
> +#define BCH_BHCR_BSEL_SHIFT		4
> +#define BCH_BHCR_BSEL_MASK		(0x7f << BCH_BHCR_BSEL_SHIFT)
> +#define BCH_BHCR_ENCE			BIT(2)
> +#define BCH_BHCR_INIT			BIT(1)
> +#define BCH_BHCR_BCHE			BIT(0)

Use of BIT() suggests you need <linux/bitops.h>. I suppose you're
covered by implicit includes for now.

> +
> +#define BCH_BHCNT_PARITYSIZE_SHIFT	16
> +#define BCH_BHCNT_PARITYSIZE_MASK	(0x7f << BCH_BHCNT_PARITYSIZE_SHIFT)
> +#define BCH_BHCNT_BLOCKSIZE_SHIFT	0
> +#define BCH_BHCNT_BLOCKSIZE_MASK	(0x7ff << BCH_BHCNT_BLOCKSIZE_SHIFT)
> +
> +#define BCH_BHERR_MASK_SHIFT		16
> +#define BCH_BHERR_MASK_MASK		(0xffff << BCH_BHERR_MASK_SHIFT)
> +#define BCH_BHERR_INDEX_SHIFT		0
> +#define BCH_BHERR_INDEX_MASK		(0x7ff << BCH_BHERR_INDEX_SHIFT)
> +
> +#define BCH_BHINT_ERRC_SHIFT		24
> +#define BCH_BHINT_ERRC_MASK		(0x7f << BCH_BHINT_ERRC_SHIFT)
> +#define BCH_BHINT_TERRC_SHIFT		16
> +#define BCH_BHINT_TERRC_MASK		(0x7f << BCH_BHINT_TERRC_SHIFT)
> +#define BCH_BHINT_DECF			BIT(3)
> +#define BCH_BHINT_ENCF			BIT(2)
> +#define BCH_BHINT_UNCOR			BIT(1)
> +#define BCH_BHINT_ERR			BIT(0)
> +
> +#define BCH_CLK_RATE			(200 * 1000 * 1000)
> +
> +/* Timeout for BCH calculation/correction in microseconds. */
> +#define BCH_TIMEOUT			100000
> +
> +struct jz4780_bch {
> +	void __iomem *base;
> +	struct clk *clk;
> +};
> +
> +static void jz4780_bch_init(struct jz4780_bch *bch,
> +			    struct jz4780_bch_params *params, bool encode)
> +{
> +	uint32_t reg;
> +
> +	/* Clear interrupt status. */
> +	writel(readl(bch->base + BCH_BHINT), bch->base + BCH_BHINT);
> +
> +	/* Set up BCH count register. */
> +	reg = params->size << BCH_BHCNT_BLOCKSIZE_SHIFT;
> +	reg |= params->bytes << BCH_BHCNT_PARITYSIZE_SHIFT;
> +	writel(reg, bch->base + BCH_BHCNT);
> +
> +	/* Initialise and enable BCH. */
> +	reg = BCH_BHCR_BCHE | BCH_BHCR_INIT;
> +	reg |= params->strength << BCH_BHCR_BSEL_SHIFT;
> +	if (encode)
> +		reg |= BCH_BHCR_ENCE;
> +	writel(reg, bch->base + BCH_BHCR);
> +}
> +
> +static void jz4780_bch_disable(struct jz4780_bch *bch)
> +{
> +	writel(readl(bch->base + BCH_BHINT), bch->base + BCH_BHINT);
> +	writel(BCH_BHCR_BCHE, bch->base + BCH_BHCCR);
> +}
> +
> +static void jz4780_bch_write_data(struct jz4780_bch *bch, const void *buf,
> +				  size_t size)
> +{
> +	size_t size32 = size / sizeof(uint32_t);
> +	size_t size8 = size & (sizeof(uint32_t) - 1);
> +	const uint32_t *src32;
> +	const uint8_t *src8;
> +
> +	src32 = (const uint32_t *)buf;
> +	while (size32--)
> +		writel(*src32++, bch->base + BCH_BHDR);
> +
> +	src8 = (const uint8_t *)src32;
> +	while (size8--)
> +		writeb(*src8++, bch->base + BCH_BHDR);
> +}
> +
> +static void jz4780_bch_read_parity(struct jz4780_bch *bch, void *buf,
> +				   size_t size)
> +{
> +	size_t size32 = size / sizeof(uint32_t);
> +	size_t size8 = size & (sizeof(uint32_t) - 1);
> +	uint32_t *dest32;
> +	uint8_t *dest8;
> +	uint32_t val, offset = 0;
> +
> +	dest32 = (uint32_t *)buf;
> +	while (size32--) {
> +		*dest32++ = readl(bch->base + BCH_BHPAR0 + offset);
> +		offset += sizeof(uint32_t);
> +	}
> +
> +	dest8 = (uint8_t *)dest32;
> +	val = readl(bch->base + BCH_BHPAR0 + offset);
> +	switch (size8) {
> +	case 3:
> +		dest8[2] = (val >> 16) & 0xff;
> +	case 2:
> +		dest8[1] = (val >> 8) & 0xff;
> +	case 1:
> +		dest8[0] = val & 0xff;
> +		break;
> +	}
> +}
> +
> +static bool jz4780_bch_wait_complete(struct jz4780_bch *bch, unsigned int irq,
> +				     uint32_t *status)
> +{
> +	uint32_t reg;
> +	int ret;
> +
> +	/*
> +	 * While we could use use interrupts here and sleep until the operation
> +	 * completes, the controller works fairly quickly (usually a few
> +	 * microseconds), so the overhead of sleeping until we get an interrupt
> +	 * actually quite noticeably decreases performance.
> +	 */
> +	ret = readl_poll_timeout(bch->base + BCH_BHINT, reg,
> +				 (reg & irq) == irq, 0, BCH_TIMEOUT);
> +	if (ret)
> +		return false;
> +
> +	if (status)
> +		*status = reg;
> +
> +	writel(reg, bch->base + BCH_BHINT);
> +	return true;
> +}
> +
> +/**
> + * jz4780_bch_calculate() - calculate ECC for a data buffer
> + * @dev: BCH device.
> + * @params: BCH parameters.
> + * @buf: input buffer with raw data.
> + * @ecc_code: output buffer with ECC.
> + *
> + * Return: 0 on success, -ETIMEDOUT if timed out while waiting for BCH
> + * controller.
> + */
> +int jz4780_bch_calculate(struct device *dev, struct jz4780_bch_params *params,
> +			 const uint8_t *buf, uint8_t *ecc_code)
> +{
> +	struct jz4780_bch *bch = dev_get_drvdata(dev);
> +	int ret = 0;
> +
> +	jz4780_bch_init(bch, params, true);
> +	jz4780_bch_write_data(bch, buf, params->size);
> +
> +	if (jz4780_bch_wait_complete(bch, BCH_BHINT_ENCF, NULL)) {
> +		jz4780_bch_read_parity(bch, ecc_code, params->bytes);
> +	} else {
> +		dev_err(dev, "timed out while calculating ECC\n");
> +		ret = -ETIMEDOUT;
> +	}
> +
> +	jz4780_bch_disable(bch);
> +	return ret;
> +}
> +EXPORT_SYMBOL(jz4780_bch_calculate);
> +
> +/**
> + * jz4780_bch_correct() - detect and correct bit errors
> + * @dev: BCH device.
> + * @params: BCH parameters.
> + * @buf: raw data read from the chip.
> + * @ecc_code: ECC read from the chip.
> + *
> + * Given the raw data and the ECC read from the NAND device, detects and
> + * corrects errors in the data.
> + *
> + * Return: the number of bit errors corrected, or -1 if there are too many
> + * errors to correct or we timed out waiting for the controller.
> + */
> +int jz4780_bch_correct(struct device *dev, struct jz4780_bch_params *params,
> +		       uint8_t *buf, uint8_t *ecc_code)
> +{
> +	struct jz4780_bch *bch = dev_get_drvdata(dev);
> +	uint32_t reg, mask, index;
> +	int i, ret, count;
> +
> +	jz4780_bch_init(bch, params, false);
> +	jz4780_bch_write_data(bch, buf, params->size);
> +	jz4780_bch_write_data(bch, ecc_code, params->bytes);
> +
> +	if (!jz4780_bch_wait_complete(bch, BCH_BHINT_DECF, &reg)) {
> +		dev_err(dev, "timed out while correcting data\n");
> +		ret = -1;
> +		goto out;
> +	}
> +
> +	if (reg & BCH_BHINT_UNCOR) {
> +		dev_warn(dev, "uncorrectable ECC error\n");
> +		ret = -1;
> +		goto out;
> +	}
> +
> +	/* Correct any detected errors. */
> +	if (reg & BCH_BHINT_ERR) {
> +		count = (reg & BCH_BHINT_ERRC_MASK) >> BCH_BHINT_ERRC_SHIFT;
> +		ret = (reg & BCH_BHINT_TERRC_MASK) >> BCH_BHINT_TERRC_SHIFT;
> +
> +		for (i = 0; i < count; i++) {
> +			reg = readl(bch->base + BCH_BHERR0 + (i * 4));
> +			mask = (reg & BCH_BHERR_MASK_MASK) >>
> +						BCH_BHERR_MASK_SHIFT;
> +			index = (reg & BCH_BHERR_INDEX_MASK) >>
> +						BCH_BHERR_INDEX_SHIFT;
> +			buf[(index * 2) + 0] ^= mask;
> +			buf[(index * 2) + 1] ^= mask >> 8;
> +		}
> +	} else {
> +		ret = 0;
> +	}
> +
> +out:
> +	jz4780_bch_disable(bch);
> +	return ret;
> +}
> +EXPORT_SYMBOL(jz4780_bch_correct);
> +
> +/**
> + * jz4780_bch_get() - get the BCH controller device
> + * @np: BCH device tree node.
> + * @dev: where to store pointer to BCH controller device.
> + *
> + * Gets the BCH controller device from the specified device tree node. The
> + * device must be released with jz4780_bch_release() when it is no longer being
> + * used.
> + *
> + * Return: 0 on success, -EPROBE_DEFER if the controller has not yet been
> + * initialised.
> + */
> +int jz4780_bch_get(struct device_node *np, struct device **dev)
> +{
> +	struct platform_device *pdev;
> +	struct jz4780_bch *bch;
> +
> +	pdev = of_find_device_by_node(np);
> +	if (!pdev || !platform_get_drvdata(pdev))
> +		return -EPROBE_DEFER;
> +
> +	get_device(&pdev->dev);
> +
> +	bch = platform_get_drvdata(pdev);
> +	clk_prepare_enable(bch->clk);
> +
> +	*dev = &pdev->dev;
> +	return 0;
> +}
> +EXPORT_SYMBOL(jz4780_bch_get);
> +
> +/**
> + * jz4780_bch_release() - release the BCH controller device
> + * @dev: BCH device.
> + */
> +void jz4780_bch_release(struct device *dev)
> +{
> +	struct jz4780_bch *bch = dev_get_drvdata(dev);
> +
> +	clk_disable_unprepare(bch->clk);
> +	put_device(dev);
> +}
> +EXPORT_SYMBOL(jz4780_bch_release);
> +
> +static int jz4780_bch_probe(struct platform_device *pdev)
> +{
> +	struct device *dev = &pdev->dev;
> +	struct jz4780_bch *bch;
> +	struct resource *res;
> +
> +	bch = devm_kzalloc(dev, sizeof(*bch), GFP_KERNEL);
> +	if (!bch)
> +		return -ENOMEM;
> +
> +	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +	bch->base = devm_ioremap_resource(dev, res);
> +	if (IS_ERR(bch->base))
> +		return PTR_ERR(bch->base);
> +
> +	jz4780_bch_disable(bch);
> +
> +	bch->clk = devm_clk_get(dev, NULL);
> +	if (IS_ERR(bch->clk)) {
> +		dev_err(dev, "failed to get clock: %ld\n", PTR_ERR(bch->clk));
> +		return PTR_ERR(bch->clk);
> +	}
> +
> +	clk_set_rate(bch->clk, BCH_CLK_RATE);
> +
> +	platform_set_drvdata(pdev, bch);
> +	return 0;
> +}
> +
> +static const struct of_device_id jz4780_bch_dt_match[] = {
> +	{ .compatible = "ingenic,jz4780-bch" },
> +	{},
> +};
> +MODULE_DEVICE_TABLE(of, jz4780_bch_dt_match);
> +
> +static struct platform_driver jz4780_bch_driver = {
> +	.probe		= jz4780_bch_probe,
> +	.driver	= {
> +		.name	= "jz4780-bch",
> +		.of_match_table = of_match_ptr(jz4780_bch_dt_match),
> +	},
> +};
> +module_platform_driver(jz4780_bch_driver);
> +
> +MODULE_AUTHOR("Alex Smith <alex.smith@...tec.com>");
> +MODULE_DESCRIPTION("Ingenic JZ4780 BCH error correction driver");
> +MODULE_LICENSE("GPL v2");
> diff --git a/drivers/mtd/nand/jz4780_bch.h b/drivers/mtd/nand/jz4780_bch.h
> new file mode 100644
> index 000000000000..a5dfde59f6ea
> --- /dev/null
> +++ b/drivers/mtd/nand/jz4780_bch.h
> @@ -0,0 +1,42 @@
> +/*
> + * JZ4780 BCH controller
> + *
> + * Copyright (c) 2015 Imagination Technologies
> + * Author: Alex Smith <alex.smith@...tec.com>
> + *
> + * 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.
> + */
> +
> +#ifndef __DRIVERS_MTD_NAND_JZ4780_BCH_H__
> +#define __DRIVERS_MTD_NAND_JZ4780_BCH_H__
> +
> +#include <linux/types.h>
> +
> +struct device;
> +struct device_node;
> +
> +/**
> + * struct jz4780_bch_params - BCH parameters
> + * @size: data bytes per ECC step.
> + * @bytes: ECC bytes per step.
> + * @strength: number of correctable bits per ECC step.
> + */
> +struct jz4780_bch_params {
> +	int size;
> +	int bytes;
> +	int strength;
> +};
> +
> +extern int jz4780_bch_calculate(struct device *dev,
> +				struct jz4780_bch_params *params,
> +				const uint8_t *buf, uint8_t *ecc_code);
> +extern int jz4780_bch_correct(struct device *dev,
> +			      struct jz4780_bch_params *params, uint8_t *buf,
> +			      uint8_t *ecc_code);
> +
> +extern int jz4780_bch_get(struct device_node *np, struct device **dev);
> +extern void jz4780_bch_release(struct device *dev);
> +
> +#endif /* __DRIVERS_MTD_NAND_JZ4780_BCH_H__ */
> diff --git a/drivers/mtd/nand/jz4780_nand.c b/drivers/mtd/nand/jz4780_nand.c
> new file mode 100644
> index 000000000000..97bd2869bedb
> --- /dev/null
> +++ b/drivers/mtd/nand/jz4780_nand.c
> @@ -0,0 +1,378 @@
> +/*
> + * JZ4780 NAND driver
> + *
> + * Copyright (c) 2015 Imagination Technologies
> + * Author: Alex Smith <alex.smith@...tec.com>
> + *
> + * 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/delay.h>
> +#include <linux/init.h>
> +#include <linux/io.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/of_address.h>
> +#include <linux/of_gpio.h>
> +#include <linux/of_mtd.h>
> +#include <linux/platform_device.h>
> +#include <linux/slab.h>
> +
> +#include <linux/mtd/mtd.h>
> +#include <linux/mtd/nand.h>
> +#include <linux/mtd/partitions.h>
> +
> +#include <linux/jz4780-nemc.h>
> +
> +#include "jz4780_bch.h"
> +
> +#define DRV_NAME	"jz4780-nand"
> +
> +#define OFFSET_DATA	0x00000000
> +#define OFFSET_CMD	0x00400000
> +#define OFFSET_ADDR	0x00800000
> +
> +/* Command delay when there is no R/B pin (in microseconds). */
> +#define RB_DELAY	100
> +
> +struct jz4780_nand_chip {
> +	unsigned int bank;
> +	void __iomem *base;
> +};
> +
> +struct jz4780_nand {
> +	struct mtd_info mtd;
> +	struct nand_chip chip;
> +
> +	struct device *dev;
> +	struct device *bch;
> +
> +	struct nand_ecclayout ecclayout;
> +
> +	int busy_gpio;
> +	int wp_gpio;
> +	unsigned int busy_gpio_active_low: 1;
> +	unsigned int wp_gpio_active_low: 1;
> +	unsigned int reading: 1;
> +
> +	unsigned int num_banks;
> +	int selected;
> +	struct jz4780_nand_chip chips[];
> +};
> +
> +static inline struct jz4780_nand *to_jz4780_nand(struct mtd_info *mtd)
> +{
> +	return container_of(mtd, struct jz4780_nand, mtd);
> +}
> +
> +static void jz4780_nand_select_chip(struct mtd_info *mtd, int chipnr)
> +{
> +	struct jz4780_nand *nand = to_jz4780_nand(mtd);
> +	struct jz4780_nand_chip *chip;
> +
> +	if (chipnr == -1) {
> +		/* Ensure the currently selected chip is deasserted. */
> +		if (nand->selected >= 0) {
> +			chip = &nand->chips[nand->selected];
> +			jz4780_nemc_assert(nand->dev, chip->bank, false);
> +		}
> +	} else {
> +		chip = &nand->chips[chipnr];
> +		nand->chip.IO_ADDR_R = chip->base + OFFSET_DATA;
> +		nand->chip.IO_ADDR_W = chip->base + OFFSET_DATA;
> +	}
> +
> +	nand->selected = chipnr;
> +}
> +
> +static void jz4780_nand_cmd_ctrl(struct mtd_info *mtd, int cmd,
> +				 unsigned int ctrl)
> +{
> +	struct jz4780_nand *nand = to_jz4780_nand(mtd);
> +	struct jz4780_nand_chip *chip;
> +
> +	if (WARN_ON(nand->selected < 0))
> +		return;
> +
> +	chip = &nand->chips[nand->selected];
> +
> +	if (ctrl & NAND_CTRL_CHANGE) {
> +		if (ctrl & NAND_ALE)
> +			nand->chip.IO_ADDR_W = chip->base + OFFSET_ADDR;
> +		else if (ctrl & NAND_CLE)
> +			nand->chip.IO_ADDR_W = chip->base + OFFSET_CMD;
> +		else
> +			nand->chip.IO_ADDR_W = chip->base + OFFSET_DATA;
> +
> +		jz4780_nemc_assert(nand->dev, chip->bank, ctrl & NAND_NCE);
> +	}
> +
> +	if (cmd != NAND_CMD_NONE)
> +		writeb(cmd, nand->chip.IO_ADDR_W);
> +}
> +
> +static int jz4780_nand_dev_ready(struct mtd_info *mtd)
> +{
> +	struct jz4780_nand *nand = to_jz4780_nand(mtd);
> +
> +	return !(gpio_get_value(nand->busy_gpio) ^ nand->busy_gpio_active_low);
> +}
> +
> +static void jz4780_nand_ecc_hwctl(struct mtd_info *mtd, int mode)
> +{
> +	struct jz4780_nand *nand = to_jz4780_nand(mtd);
> +
> +	nand->reading = (mode == NAND_ECC_READ);
> +}
> +
> +static int jz4780_nand_ecc_calculate(struct mtd_info *mtd, const uint8_t *dat,
> +				     uint8_t *ecc_code)
> +{
> +	struct jz4780_nand *nand = to_jz4780_nand(mtd);
> +	struct jz4780_bch_params params;
> +
> +	/*
> +	 * Don't need to generate the ECC when reading, BCH does it for us as
> +	 * part of decoding/correction.
> +	 */
> +	if (nand->reading)
> +		return 0;
> +
> +	params.size = nand->chip.ecc.size;
> +	params.bytes = nand->chip.ecc.bytes;
> +	params.strength = nand->chip.ecc.strength;
> +
> +	return jz4780_bch_calculate(nand->bch, &params, dat, ecc_code);
> +}
> +
> +static int jz4780_nand_ecc_correct(struct mtd_info *mtd, uint8_t *dat,
> +				   uint8_t *read_ecc, uint8_t *calc_ecc)
> +{
> +	struct jz4780_nand *nand = to_jz4780_nand(mtd);
> +	struct jz4780_bch_params params;
> +
> +	params.size = nand->chip.ecc.size;
> +	params.bytes = nand->chip.ecc.bytes;
> +	params.strength = nand->chip.ecc.strength;
> +
> +	return jz4780_bch_correct(nand->bch, &params, dat, read_ecc);
> +}
> +
> +static void jz4780_nand_init_ecc(struct jz4780_nand *nand, struct device *dev)
> +{
> +	struct mtd_info *mtd = &nand->mtd;
> +	struct nand_chip *chip = &nand->chip;
> +	struct nand_ecclayout *layout = &nand->ecclayout;
> +	uint32_t start, i;
> +
> +	chip->ecc.size = of_get_nand_ecc_step_size(dev->of_node);
> +	if (chip->ecc.size < 0)
> +		chip->ecc.size = 1024;
> +
> +	chip->ecc.strength = of_get_nand_ecc_strength(dev->of_node);
> +	if (chip->ecc.strength < 0)
> +		chip->ecc.strength = 24;

Can you make use of nand_dt_init()? That means you'd also need to
specify the generic "nand-ecc-mode" property in your DT, then initialize
chip->flash_node before running nand_scan_ident().

> +
> +	chip->ecc.bytes = fls(1 + 8 * chip->ecc.size) * chip->ecc.strength / 8;
> +
> +	dev_info(dev, "using %s BCH (strength %d, size %d, bytes %d)\n",
> +		 (nand->bch) ? "hardware" : "software", chip->ecc.strength,
> +		 chip->ecc.size, chip->ecc.bytes);
> +
> +	if (nand->bch) {
> +		chip->ecc.mode = NAND_ECC_HW;
> +		chip->ecc.hwctl = jz4780_nand_ecc_hwctl;
> +		chip->ecc.calculate = jz4780_nand_ecc_calculate;
> +		chip->ecc.correct = jz4780_nand_ecc_correct;
> +	} else {
> +		chip->ecc.mode = NAND_ECC_SOFT_BCH;
> +	}
> +
> +	/* Generate ECC layout. ECC codes are right aligned in the OOB area. */
> +	layout->eccbytes = mtd->writesize / chip->ecc.size * chip->ecc.bytes;
> +	start = mtd->oobsize - layout->eccbytes;
> +	for (i = 0; i < layout->eccbytes; i++)
> +		layout->eccpos[i] = start + i;
> +
> +	layout->oobfree[0].offset = 2;
> +	layout->oobfree[0].length = mtd->oobsize - layout->eccbytes - 2;
> +
> +	chip->ecc.layout = layout;
> +}
> +
> +static int jz4780_nand_init_chips(struct jz4780_nand *nand,
> +				  struct platform_device *pdev)
> +{
> +	struct device *dev = &pdev->dev;
> +	struct jz4780_nand_chip *chip;
> +	const __be32 *prop;
> +	struct resource *res;
> +	int i = 0;
> +
> +	/*
> +	 * Iterate over each bank assigned to this device and request resources.
> +	 * The bank numbers may not be consecutive, but nand_scan_ident()
> +	 * expects chip numbers to be, so fill out a consecutive array of chips
> +	 * which map chip number to actual bank number.
> +	 */

Hmm, this is an interesting point. Do we really want to lump multiple
banks in the same device tree node? I've seen the history (nand_scan*()
supports multipe chips in a single nand_scan*() call) but this can be
limiting. What if you have two non-identical flash?

IOW, would following a pattern like the following make more sense? With
these, each separate flash gets its own device node:

https://www.kernel.org/doc/Documentation/devicetree/bindings/mtd/sunxi-nand.txt
https://www.kernel.org/doc/Documentation/devicetree/bindings/mtd/brcm,brcmnand.txt

> +	while ((prop = of_get_address(dev->of_node, i, NULL, NULL))) {
> +		chip = &nand->chips[i];
> +		chip->bank = of_read_number(prop, 1);
> +
> +		jz4780_nemc_set_type(nand->dev, chip->bank,
> +				     JZ4780_NEMC_BANK_NAND);
> +
> +		res = platform_get_resource(pdev, IORESOURCE_MEM, i);
> +		chip->base = devm_ioremap_resource(dev, res);
> +		if (IS_ERR(chip->base)) {
> +			dev_err(dev, "failed to map bank %u: %ld\n",
> +				chip->bank, PTR_ERR(chip->base));
> +			return PTR_ERR(chip->base);
> +		}
> +
> +		i++;
> +	}
> +
> +	return 0;
> +}
> +
> +static int jz4780_nand_probe(struct platform_device *pdev)
> +{
> +	struct device *dev = &pdev->dev;
> +	unsigned int num_banks;
> +	struct jz4780_nand *nand;
> +	struct device_node *bch_np;
> +	struct mtd_info *mtd;
> +	struct nand_chip *chip;
> +	enum of_gpio_flags flags;
> +	struct mtd_part_parser_data ppdata;
> +	int ret;
> +
> +	num_banks = jz4780_nemc_num_banks(dev);

Should we handle the num_banks==0 case?

> +
> +	nand = devm_kzalloc(dev,
> +			sizeof(*nand) + (sizeof(nand->chips[0]) * num_banks),
> +			GFP_KERNEL);
> +	if (!nand)
> +		return -ENOMEM;
> +
> +	nand->dev = dev;
> +	nand->num_banks = num_banks;
> +	nand->selected = -1;
> +
> +	/* Look for the BCH controller. */
> +	bch_np = of_parse_phandle(dev->of_node, "ingenic,bch-controller", 0);
> +	if (bch_np) {
> +		ret = jz4780_bch_get(bch_np, &nand->bch);
> +		of_node_put(bch_np);
> +		if (ret)
> +			return ret;
> +	}
> +
> +	mtd = &nand->mtd;
> +	chip = &nand->chip;
> +	mtd->priv = chip;
> +	mtd->owner = THIS_MODULE;
> +	mtd->name = DRV_NAME;
> +	mtd->dev.parent = dev;
> +
> +	chip->chip_delay = RB_DELAY;
> +	chip->options = NAND_NO_SUBPAGE_WRITE;
> +	chip->bbt_options = NAND_BBT_USE_FLASH;

Might use the "nand-on-flash-bbt" DT property, and nand_dt_init() will
handle this for you automagically?

> +	chip->select_chip = jz4780_nand_select_chip;
> +	chip->cmd_ctrl = jz4780_nand_cmd_ctrl;
> +
> +	nand->busy_gpio = of_get_named_gpio_flags(dev->of_node,
> +						  "rb-gpios",
> +						  0, &flags);

Note (for future reference, not for your immediate action): this binding
is shared with at least sunxi-nand. We could probably share the (simple)
code for it too by moving this to nand_base.

> +	if (gpio_is_valid(nand->busy_gpio)) {
> +		ret = devm_gpio_request(dev, nand->busy_gpio, "NAND busy");
> +		if (ret) {
> +			dev_err(dev, "failed to request busy GPIO %d: %d\n",
> +				nand->busy_gpio, ret);
> +			goto err_release_bch;
> +		}
> +
> +		nand->busy_gpio_active_low = flags & OF_GPIO_ACTIVE_LOW;
> +		gpio_direction_input(nand->busy_gpio);
> +
> +		chip->dev_ready = jz4780_nand_dev_ready;
> +	}
> +
> +	nand->wp_gpio = of_get_named_gpio_flags(dev->of_node, "wp-gpios",
> +						0, &flags);

Another note (again, not necessarily for your your immediate action):
this binding was requested for other drivers. Having some kind of
support code for it in nand_base could be helpful, even if it's just as
simple as to disable WP at startup. I have also seen cases where users
want a way to control WP policy -- e.g., to only disable WP when
reprogramming, so that it's more difficult to experience spurious writes
to the flash due to flaky HW. So handling that in the core driver could
be useful. But not your problem.

> +	if (gpio_is_valid(nand->wp_gpio)) {
> +		ret = devm_gpio_request(dev, nand->wp_gpio, "NAND WP");
> +		if (ret) {
> +			dev_err(dev, "failed to request WP GPIO %d: %d\n",
> +				nand->wp_gpio, ret);
> +			goto err_release_bch;
> +		}
> +
> +		nand->wp_gpio_active_low = flags & OF_GPIO_ACTIVE_LOW;
> +		gpio_direction_output(nand->wp_gpio, nand->wp_gpio_active_low);
> +	}
> +
> +	ret = jz4780_nand_init_chips(nand, pdev);
> +	if (ret)
> +		goto err_release_bch;
> +
> +	ret = nand_scan_ident(mtd, num_banks, NULL);
> +	if (ret)
> +		goto err_release_bch;
> +
> +	jz4780_nand_init_ecc(nand, dev);
> +
> +	ret = nand_scan_tail(mtd);
> +	if (ret)
> +		goto err_release_bch;
> +
> +	ppdata.of_node = dev->of_node;
> +	ret = mtd_device_parse_register(mtd, NULL, &ppdata, NULL, 0);
> +	if (ret)
> +		goto err_release_nand;
> +
> +	platform_set_drvdata(pdev, nand);
> +	return 0;
> +
> +err_release_nand:
> +	nand_release(mtd);
> +
> +err_release_bch:
> +	if (nand->bch)
> +		jz4780_bch_release(nand->bch);
> +
> +	return ret;
> +}
> +
> +static int jz4780_nand_remove(struct platform_device *pdev)
> +{
> +	struct jz4780_nand *nand = platform_get_drvdata(pdev);
> +
> +	if (nand->bch)
> +		jz4780_bch_release(nand->bch);
> +
> +	return 0;
> +}
> +
> +static const struct of_device_id jz4780_nand_dt_match[] = {
> +	{ .compatible = "ingenic,jz4780-nand" },
> +	{},
> +};
> +MODULE_DEVICE_TABLE(of, jz4780_nand_dt_match);
> +
> +static struct platform_driver jz4780_nand_driver = {
> +	.probe		= jz4780_nand_probe,
> +	.remove		= jz4780_nand_remove,
> +	.driver	= {
> +		.name	= DRV_NAME,
> +		.of_match_table = of_match_ptr(jz4780_nand_dt_match),
> +	},
> +};
> +module_platform_driver(jz4780_nand_driver);
> +
> +MODULE_AUTHOR("Alex Smith <alex.smith@...tec.com>");
> +MODULE_DESCRIPTION("Ingenic JZ4780 NAND driver");
> +MODULE_LICENSE("GPL v2");

Brian
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