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Date:   Tue, 22 May 2018 16:53:46 +0200
From:   Stefan Agner <stefan@agner.ch>
To:     boris.brezillon@bootlin.com, dwmw2@infradead.org,
        computersforpeace@gmail.com, marek.vasut@gmail.com,
        robh+dt@kernel.org, mark.rutland@arm.com, thierry.reding@gmail.com,
        mturquette@baylibre.com, sboyd@kernel.org
Cc:     dev@lynxeye.de, miquel.raynal@bootlin.com, richard@nod.at,
        marcel@ziswiler.com, krzk@kernel.org, digetx@gmail.com,
        benjamin.lindqvist@endian.se, jonathanh@nvidia.com,
        pdeschrijver@nvidia.com, pgaikwad@nvidia.com, mirza.krak@gmail.com,
        linux-mtd@lists.infradead.org, linux-tegra@vger.kernel.org,
        devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-clk@vger.kernel.org
Subject: Re: [RESEND PATCH 2/5] mtd: rawnand: add NVIDIA Tegra NAND Flash
 controller driver
In-Reply-To: <86fdf19ec92b732709732fb60199f16488b4b727.1526990589.git.stefan@agner.ch>
References: <cover.1526990589.git.stefan@agner.ch>
 <86fdf19ec92b732709732fb60199f16488b4b727.1526990589.git.stefan@agner.ch>
Message-ID: <4e19315d0c44d3f9b7ffb63216f2c179@agner.ch>
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Hi,

I do have some questions for some areas I wanted to improve in the next
revision. But I would like to make sure that the way I would like to
implement aligns with the MTD subsystem.

On 22.05.2018 14:07, Stefan Agner wrote:
> Add support for the NAND flash controller found on NVIDIA
> Tegra 2 SoCs. This implementation does not make use of the
> command queue feature. Regular operations/data transfers are
> done in PIO mode. Page read/writes with hardware ECC make
> use of the DMA for data transfer.
> 
> Signed-off-by: Lucas Stach <dev@lynxeye.de>
> Signed-off-by: Stefan Agner <stefan@agner.ch>
> ---
>  MAINTAINERS                       |   7 +
>  drivers/mtd/nand/raw/Kconfig      |   6 +
>  drivers/mtd/nand/raw/Makefile     |   1 +
>  drivers/mtd/nand/raw/tegra_nand.c | 915 ++++++++++++++++++++++++++++++
>  4 files changed, 929 insertions(+)
>  create mode 100644 drivers/mtd/nand/raw/tegra_nand.c
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 58b9861ccf99..a65739681279 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -13844,6 +13844,13 @@ M:	Laxman Dewangan <ldewangan@nvidia.com>
>  S:	Supported
>  F:	drivers/input/keyboard/tegra-kbc.c
>  
> +TEGRA NAND DRIVER
> +M:	Stefan Agner <stefan@agner.ch>
> +M:	Lucas Stach <dev@lynxeye.de>
> +S:	Maintained
> +F:	Documentation/devicetree/bindings/mtd/nvidia,tegra20-nand.txt
> +F:	drivers/mtd/nand/tegra_nand.c
> +
>  TEGRA PWM DRIVER
>  M:	Thierry Reding <thierry.reding@gmail.com>
>  S:	Supported
> diff --git a/drivers/mtd/nand/raw/Kconfig b/drivers/mtd/nand/raw/Kconfig
> index 19a2b283fbbe..bd56264233ca 100644
> --- a/drivers/mtd/nand/raw/Kconfig
> +++ b/drivers/mtd/nand/raw/Kconfig
> @@ -534,4 +534,10 @@ config MTD_NAND_MTK
>  	  Enables support for NAND controller on MTK SoCs.
>  	  This controller is found on mt27xx, mt81xx, mt65xx SoCs.
>  
> +config MTD_NAND_TEGRA
> +	tristate "Support for NAND on NVIDIA Tegra"
> +	depends on ARCH_TEGRA
> +	help
> +	  Enables support for NAND flash on NVIDIA Tegra SoC based boards.
> +
>  endif # MTD_NAND
> diff --git a/drivers/mtd/nand/raw/Makefile b/drivers/mtd/nand/raw/Makefile
> index 165b7ef9e9a1..d5a5f9832b88 100644
> --- a/drivers/mtd/nand/raw/Makefile
> +++ b/drivers/mtd/nand/raw/Makefile
> @@ -56,6 +56,7 @@ obj-$(CONFIG_MTD_NAND_HISI504)	        += hisi504_nand.o
>  obj-$(CONFIG_MTD_NAND_BRCMNAND)		+= brcmnand/
>  obj-$(CONFIG_MTD_NAND_QCOM)		+= qcom_nandc.o
>  obj-$(CONFIG_MTD_NAND_MTK)		+= mtk_ecc.o mtk_nand.o
> +obj-$(CONFIG_MTD_NAND_TEGRA)		+= tegra_nand.o
>  
>  nand-objs := nand_base.o nand_bbt.o nand_timings.o nand_ids.o
>  nand-objs += nand_amd.o
> diff --git a/drivers/mtd/nand/raw/tegra_nand.c
> b/drivers/mtd/nand/raw/tegra_nand.c
> new file mode 100644
> index 000000000000..fa236e683fb8
> --- /dev/null
> +++ b/drivers/mtd/nand/raw/tegra_nand.c
> @@ -0,0 +1,915 @@
> +/*
> + * Copyright (C) 2018 Stefan Agner <stefan@agner.ch>
> + * Copyright (C) 2014-2015 Lucas Stach <dev@lynxeye.de>
> + * Copyright (C) 2012 Avionic Design GmbH
> + *
> + * 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/completion.h>
> +#include <linux/delay.h>
> +#include <linux/dma-mapping.h>
> +#include <linux/err.h>
> +#include <linux/gpio/consumer.h>
> +#include <linux/interrupt.h>
> +#include <linux/io.h>
> +#include <linux/module.h>
> +#include <linux/mtd/partitions.h>
> +#include <linux/mtd/rawnand.h>
> +#include <linux/of.h>
> +#include <linux/platform_device.h>
> +#include <linux/reset.h>
> +
> +#define CMD					0x00
> +#define   CMD_GO				(1 << 31)
> +#define   CMD_CLE				(1 << 30)
> +#define   CMD_ALE				(1 << 29)
> +#define   CMD_PIO				(1 << 28)
> +#define   CMD_TX				(1 << 27)
> +#define   CMD_RX				(1 << 26)
> +#define   CMD_SEC_CMD				(1 << 25)
> +#define   CMD_AFT_DAT				(1 << 24)
> +#define   CMD_TRANS_SIZE(x)			(((x - 1) & 0xf) << 20)
> +#define   CMD_A_VALID				(1 << 19)
> +#define   CMD_B_VALID				(1 << 18)
> +#define   CMD_RD_STATUS_CHK			(1 << 17)
> +#define   CMD_RBSY_CHK				(1 << 16)
> +#define   CMD_CE(x)				(1 << (8 + ((x) & 0x7)))
> +#define   CMD_CLE_SIZE(x)			(((x - 1) & 0x3) << 4)
> +#define   CMD_ALE_SIZE(x)			(((x - 1) & 0xf) << 0)
> +
> +#define STATUS					0x04
> +
> +#define ISR					0x08
> +#define   ISR_CORRFAIL_ERR			(1 << 24)
> +#define   ISR_UND				(1 << 7)
> +#define   ISR_OVR				(1 << 6)
> +#define   ISR_CMD_DONE				(1 << 5)
> +#define   ISR_ECC_ERR				(1 << 4)
> +
> +#define IER					0x0c
> +#define   IER_ERR_TRIG_VAL(x)			(((x) & 0xf) << 16)
> +#define   IER_UND				(1 << 7)
> +#define   IER_OVR				(1 << 6)
> +#define   IER_CMD_DONE				(1 << 5)
> +#define   IER_ECC_ERR				(1 << 4)
> +#define   IER_GIE				(1 << 0)
> +
> +#define CFG					0x10
> +#define   CFG_HW_ECC				(1 << 31)
> +#define   CFG_ECC_SEL				(1 << 30)
> +#define   CFG_ERR_COR				(1 << 29)
> +#define   CFG_PIPE_EN				(1 << 28)
> +#define   CFG_TVAL_4				(0 << 24)
> +#define   CFG_TVAL_6				(1 << 24)
> +#define   CFG_TVAL_8				(2 << 24)
> +#define   CFG_SKIP_SPARE			(1 << 23)
> +#define   CFG_BUS_WIDTH_8			(0 << 21)
> +#define   CFG_BUS_WIDTH_16			(1 << 21)
> +#define   CFG_COM_BSY				(1 << 20)
> +#define   CFG_PS_256				(0 << 16)
> +#define   CFG_PS_512				(1 << 16)
> +#define   CFG_PS_1024				(2 << 16)
> +#define   CFG_PS_2048				(3 << 16)
> +#define   CFG_PS_4096				(4 << 16)
> +#define   CFG_SKIP_SPARE_SIZE_4			(0 << 14)
> +#define   CFG_SKIP_SPARE_SIZE_8			(1 << 14)
> +#define   CFG_SKIP_SPARE_SIZE_12		(2 << 14)
> +#define   CFG_SKIP_SPARE_SIZE_16		(3 << 14)
> +#define   CFG_TAG_BYTE_SIZE(x)			((x) & 0xff)
> +
> +#define TIMING_1				0x14
> +#define   TIMING_TRP_RESP(x)			(((x) & 0xf) << 28)
> +#define   TIMING_TWB(x)				(((x) & 0xf) << 24)
> +#define   TIMING_TCR_TAR_TRR(x)			(((x) & 0xf) << 20)
> +#define   TIMING_TWHR(x)			(((x) & 0xf) << 16)
> +#define   TIMING_TCS(x)				(((x) & 0x3) << 14)
> +#define   TIMING_TWH(x)				(((x) & 0x3) << 12)
> +#define   TIMING_TWP(x)				(((x) & 0xf) <<  8)
> +#define   TIMING_TRH(x)				(((x) & 0xf) <<  4)
> +#define   TIMING_TRP(x)				(((x) & 0xf) <<  0)
> +
> +#define RESP					0x18
> +
> +#define TIMING_2				0x1c
> +#define   TIMING_TADL(x)			((x) & 0xf)
> +
> +#define CMD_1					0x20
> +#define CMD_2					0x24
> +#define ADDR_1					0x28
> +#define ADDR_2					0x2c
> +
> +#define DMA_CTRL				0x30
> +#define   DMA_CTRL_GO				(1 << 31)
> +#define   DMA_CTRL_IN				(0 << 30)
> +#define   DMA_CTRL_OUT				(1 << 30)
> +#define   DMA_CTRL_PERF_EN			(1 << 29)
> +#define   DMA_CTRL_IE_DONE			(1 << 28)
> +#define   DMA_CTRL_REUSE			(1 << 27)
> +#define   DMA_CTRL_BURST_1			(2 << 24)
> +#define   DMA_CTRL_BURST_4			(3 << 24)
> +#define   DMA_CTRL_BURST_8			(4 << 24)
> +#define   DMA_CTRL_BURST_16			(5 << 24)
> +#define   DMA_CTRL_IS_DONE			(1 << 20)
> +#define   DMA_CTRL_EN_A				(1 <<  2)
> +#define   DMA_CTRL_EN_B				(1 <<  1)
> +
> +#define DMA_CFG_A				0x34
> +#define DMA_CFG_B				0x38
> +
> +#define FIFO_CTRL				0x3c
> +#define   FIFO_CTRL_CLR_ALL			(1 << 3)
> +
> +#define DATA_PTR				0x40
> +#define TAG_PTR					0x44
> +#define ECC_PTR					0x48
> +
> +#define DEC_STATUS				0x4c
> +#define   DEC_STATUS_A_ECC_FAIL			(1 << 1)
> +#define   DEC_STATUS_ERR_COUNT_MASK		0x00ff0000
> +#define   DEC_STATUS_ERR_COUNT_SHIFT		16
> +
> +#define HWSTATUS_CMD				0x50
> +#define HWSTATUS_MASK				0x54
> +#define   HWSTATUS_RDSTATUS_MASK(x)		(((x) & 0xff) << 24)
> +#define   HWSTATUS_RDSTATUS_VALUE(x)		(((x) & 0xff) << 16)
> +#define   HWSTATUS_RBSY_MASK(x)			(((x) & 0xff) << 8)
> +#define   HWSTATUS_RBSY_VALUE(x)		(((x) & 0xff) << 0)
> +
> +#define DEC_STAT_RESULT				0xd0
> +#define DEC_STAT_BUF				0xd4
> +#define   DEC_STAT_BUF_CORR_SEC_FLAG_MASK	0x00ff0000
> +#define   DEC_STAT_BUF_CORR_SEC_FLAG_SHIFT	16
> +#define   DEC_STAT_BUF_MAX_CORR_CNT_MASK	0x00001f00
> +#define   DEC_STAT_BUF_MAX_CORR_CNT_SHIFT	8
> +
> +struct tegra_nand {
> +	void __iomem *regs;
> +	struct clk *clk;
> +	struct gpio_desc *wp_gpio;
> +
> +	struct nand_chip chip;
> +	struct device *dev;
> +
> +	struct completion command_complete;
> +	struct completion dma_complete;
> +	bool last_read_error;
> +
> +	dma_addr_t data_dma;
> +	void *data_buf;
> +	dma_addr_t oob_dma;
> +	void *oob_buf;
> +
> +	int cur_chip;
> +};
> +
> +static inline struct tegra_nand *to_tegra_nand(struct mtd_info *mtd)
> +{
> +	struct nand_chip *chip = mtd_to_nand(mtd);
> +
> +	return nand_get_controller_data(chip);
> +}
> +
> +static int tegra_nand_ooblayout_16_ecc(struct mtd_info *mtd, int section,
> +				       struct mtd_oob_region *oobregion)
> +{
> +	if (section > 0)
> +		return -ERANGE;
> +
> +	oobregion->offset = 4;
> +	oobregion->length = 4;
> +
> +	return 0;
> +}
> +
> +static int tegra_nand_ooblayout_16_free(struct mtd_info *mtd, int section,
> +					struct mtd_oob_region *oobregion)
> +{
> +	if (section > 0)
> +		return -ERANGE;
> +
> +	oobregion->offset = 8;
> +	oobregion->length = 8;
> +
> +	return 0;
> +}
> +
> +static const struct mtd_ooblayout_ops tegra_nand_oob_16_ops = {
> +	.ecc = tegra_nand_ooblayout_16_ecc,
> +	.free = tegra_nand_ooblayout_16_free,
> +};
> +
> +static int tegra_nand_ooblayout_64_ecc(struct mtd_info *mtd, int section,
> +				       struct mtd_oob_region *oobregion)
> +{
> +	if (section > 0)
> +		return -ERANGE;
> +
> +	oobregion->offset = 4;
> +	oobregion->length = 36;
> +
> +	return 0;
> +}
> +
> +static int tegra_nand_ooblayout_64_free(struct mtd_info *mtd, int section,
> +					struct mtd_oob_region *oobregion)
> +{
> +	if (section > 0)
> +		return -ERANGE;
> +
> +	oobregion->offset = 40;
> +	oobregion->length = 24;
> +
> +	return 0;
> +}
> +
> +static const struct mtd_ooblayout_ops tegra_nand_oob_64_ops = {
> +	.ecc = tegra_nand_ooblayout_64_ecc,
> +	.free = tegra_nand_ooblayout_64_free,
> +};
> +
> +static int tegra_nand_ooblayout_128_ecc(struct mtd_info *mtd, int section,
> +				       struct mtd_oob_region *oobregion)
> +{
> +	if (section > 0)
> +		return -ERANGE;
> +
> +	oobregion->offset = 4;
> +	oobregion->length = 72;
> +
> +	return 0;
> +}
> +
> +static int tegra_nand_ooblayout_128_free(struct mtd_info *mtd, int section,
> +					struct mtd_oob_region *oobregion)
> +{
> +	if (section > 0)
> +		return -ERANGE;
> +
> +	oobregion->offset = 76;
> +	oobregion->length = 52;
> +
> +	return 0;
> +}
> +
> +static const struct mtd_ooblayout_ops tegra_nand_oob_128_ops = {
> +	.ecc = tegra_nand_ooblayout_128_ecc,
> +	.free = tegra_nand_ooblayout_128_free,
> +};
> +
> +static int tegra_nand_ooblayout_224_ecc(struct mtd_info *mtd, int section,
> +				       struct mtd_oob_region *oobregion)
> +{
> +	if (section > 0)
> +		return -ERANGE;
> +
> +	oobregion->offset = 4;
> +	oobregion->length = 144;
> +
> +	return 0;
> +}
> +
> +static int tegra_nand_ooblayout_224_free(struct mtd_info *mtd, int section,
> +					struct mtd_oob_region *oobregion)
> +{
> +	if (section > 0)
> +		return -ERANGE;
> +
> +	oobregion->offset = 148;
> +	oobregion->length = 76;
> +
> +	return 0;
> +}
> +
> +static const struct mtd_ooblayout_ops tegra_nand_oob_224_ops = {
> +	.ecc = tegra_nand_ooblayout_224_ecc,
> +	.free = tegra_nand_ooblayout_224_free,
> +};

The layout mostly depends on algorithm used. So for Reed-Solomon with
maximum symbol error of 8 it is probably better to create something
like:

static const struct mtd_ooblayout_ops tegra_nand_oob_rs_8_ops = {
	.ecc = tegra_nand_ooblayout_rs_8_ecc,
	.free = tegra_nand_ooblayout_rs_8_free,
};

And then use mtd->writesize/mtd->oobsize to calculate offset/length?

> +
> +static irqreturn_t tegra_nand_irq(int irq, void *data)
> +{
> +	struct tegra_nand *nand = data;
> +	u32 isr, dma;
> +
> +	isr = readl(nand->regs + ISR);
> +	dma = readl(nand->regs + DMA_CTRL);
> +	dev_dbg(nand->dev, "isr %08x\n", isr);
> +
> +	if (!isr && !(dma & DMA_CTRL_IS_DONE))
> +		return IRQ_NONE;
> +
> +	if (isr & ISR_CORRFAIL_ERR)
> +		nand->last_read_error = true;
> +
> +	if (isr & ISR_CMD_DONE)
> +		complete(&nand->command_complete);
> +
> +	if (isr & ISR_UND)
> +		dev_dbg(nand->dev, "FIFO underrun\n");
> +
> +	if (isr & ISR_OVR)
> +		dev_dbg(nand->dev, "FIFO overrun\n");
> +
> +	/* handle DMA interrupts */
> +	if (dma & DMA_CTRL_IS_DONE) {
> +		writel(dma, nand->regs + DMA_CTRL);
> +		complete(&nand->dma_complete);
> +	}
> +
> +	/* clear interrupts */
> +	writel(isr, nand->regs + ISR);
> +
> +	return IRQ_HANDLED;
> +}
> +
> +static int tegra_nand_cmd(struct nand_chip *chip,
> +			 const struct nand_subop *subop)
> +{
> +	const struct nand_op_instr *instr;
> +	const struct nand_op_instr *instr_data_in = NULL;
> +	struct mtd_info *mtd = nand_to_mtd(chip);
> +	struct tegra_nand *nand = to_tegra_nand(mtd);
> +	unsigned int op_id = -1, trfr_in_sz = 0, trfr_out_sz = 0, offset = 0;
> +	bool first_cmd = true;
> +	bool force8bit;
> +	u32 cmd = 0;
> +	u32 value;
> +
> +	for (op_id = 0; op_id < subop->ninstrs; op_id++) {
> +		unsigned int naddrs, i;
> +		const u8 *addrs;
> +		u32 addr1 = 0, addr2 = 0;
> +
> +		instr = &subop->instrs[op_id];
> +
> +		switch (instr->type) {
> +		case NAND_OP_CMD_INSTR:
> +			if (first_cmd) {
> +				cmd |= CMD_CLE;
> +				writel(instr->ctx.cmd.opcode, nand->regs + CMD_1);
> +			} else {
> +				cmd |= CMD_SEC_CMD;
> +				writel(instr->ctx.cmd.opcode, nand->regs + CMD_2);
> +			}
> +			first_cmd = false;
> +			break;
> +		case NAND_OP_ADDR_INSTR:
> +			offset = nand_subop_get_addr_start_off(subop, op_id);
> +			naddrs = nand_subop_get_num_addr_cyc(subop, op_id);
> +			addrs = &instr->ctx.addr.addrs[offset];
> +
> +			cmd |= CMD_ALE | CMD_ALE_SIZE(naddrs);
> +			for (i = 0; i < min_t(unsigned int, 4, naddrs); i++)
> +				addr1 |= *addrs++ << (8 * i);
> +			naddrs -= i;
> +			for (i = 0; i < min_t(unsigned int, 4, naddrs); i++)
> +				addr2 |= *addrs++ << (8 * i);
> +			writel(addr1, nand->regs + ADDR_1);
> +			writel(addr2, nand->regs + ADDR_2);
> +			break;
> +
> +		case NAND_OP_DATA_IN_INSTR:
> +			trfr_in_sz = nand_subop_get_data_len(subop, op_id);
> +			offset = nand_subop_get_data_start_off(subop, op_id);
> +
> +			cmd |= CMD_TRANS_SIZE(trfr_in_sz) | CMD_PIO | CMD_RX | CMD_A_VALID;
> +
> +			instr_data_in = instr;
> +			break;
> +
> +		case NAND_OP_DATA_OUT_INSTR:
> +			trfr_out_sz = nand_subop_get_data_len(subop, op_id);
> +			offset = nand_subop_get_data_start_off(subop, op_id);
> +			trfr_out_sz = min_t(size_t, trfr_out_sz, 4);
> +
> +			cmd |= CMD_TRANS_SIZE(trfr_out_sz) | CMD_PIO | CMD_TX | CMD_A_VALID;
> +
> +			memcpy(&value, instr->ctx.data.buf.out + offset, trfr_out_sz);
> +			writel(value, nand->regs + RESP);
> +
> +			break;
> +		case NAND_OP_WAITRDY_INSTR:
> +			cmd |= CMD_RBSY_CHK;
> +			break;
> +
> +		}
> +	}
> +
> +
> +	cmd |= CMD_GO | CMD_CE(nand->cur_chip);
> +	writel(cmd, nand->regs + CMD);
> +	wait_for_completion(&nand->command_complete);
> +
> +	if (instr_data_in) {
> +		u32 value;
> +		size_t n = min_t(size_t, trfr_in_sz, 4);
> +
> +		value = readl(nand->regs + RESP);
> +		memcpy(instr_data_in->ctx.data.buf.in + offset, &value, n);
> +	}
> +
> +	return 0;
> +}
> +
> +static const struct nand_op_parser tegra_nand_op_parser = NAND_OP_PARSER(
> +	NAND_OP_PARSER_PATTERN(tegra_nand_cmd,
> +		NAND_OP_PARSER_PAT_CMD_ELEM(true),
> +		NAND_OP_PARSER_PAT_ADDR_ELEM(true, 8),
> +		NAND_OP_PARSER_PAT_CMD_ELEM(true),
> +		NAND_OP_PARSER_PAT_WAITRDY_ELEM(true)),
> +	NAND_OP_PARSER_PATTERN(tegra_nand_cmd,
> +		NAND_OP_PARSER_PAT_DATA_OUT_ELEM(false, 4)),
> +	NAND_OP_PARSER_PATTERN(tegra_nand_cmd,
> +		NAND_OP_PARSER_PAT_CMD_ELEM(true),
> +		NAND_OP_PARSER_PAT_ADDR_ELEM(true, 8),
> +		NAND_OP_PARSER_PAT_CMD_ELEM(true),
> +		NAND_OP_PARSER_PAT_WAITRDY_ELEM(true),
> +		NAND_OP_PARSER_PAT_DATA_IN_ELEM(true, 4)),
> +	);
> +
> +static int tegra_nand_exec_op(struct nand_chip *chip,
> +			     const struct nand_operation *op,
> +			     bool check_only)
> +{
> +	return nand_op_parser_exec_op(chip, &tegra_nand_op_parser, op,
> +				      check_only);
> +}
> +static void tegra_nand_select_chip(struct mtd_info *mtd, int chip)
> +{
> +	struct tegra_nand *nand = to_tegra_nand(mtd);
> +
> +	nand->cur_chip = chip;
> +}
> +
> +static u32 tegra_nand_fill_address(struct mtd_info *mtd, struct
> nand_chip *chip,
> +				   int page)
> +{
> +	struct tegra_nand *nand = to_tegra_nand(mtd);
> +
> +	/* Lower 16-bits are column, always 0 */
> +	writel(page << 16, nand->regs + ADDR_1);
> +
> +	if (chip->options & NAND_ROW_ADDR_3) {
> +		writel(page >> 16, nand->regs + ADDR_2);
> +		return 5;
> +	}
> +
> +	return 4;
> +}
> +
> +static int tegra_nand_read_page(struct mtd_info *mtd, struct nand_chip *chip,
> +				uint8_t *buf, int oob_required, int page)
> +{
> +	struct tegra_nand *nand = to_tegra_nand(mtd);
> +	u32 value, addrs;
> +
> +	writel(NAND_CMD_READ0, nand->regs + CMD_1);
> +	writel(NAND_CMD_READSTART, nand->regs + CMD_2);
> +
> +	addrs = tegra_nand_fill_address(mtd, chip, page);
> +
> +	value = readl(nand->regs + CFG);
> +	value |= CFG_HW_ECC | CFG_ERR_COR;
> +	writel(value, nand->regs + CFG);
> +
> +	writel(mtd->writesize - 1, nand->regs + DMA_CFG_A);
> +	writel(nand->data_dma, nand->regs + DATA_PTR);
> +
> +	if (oob_required) {
> +		writel(mtd_ooblayout_count_freebytes(mtd) - 1,
> +		       nand->regs + DMA_CFG_B);
> +		writel(nand->oob_dma, nand->regs + TAG_PTR);
> +	} else {
> +		writel(0, nand->regs + DMA_CFG_B);
> +		writel(0, nand->regs + TAG_PTR);
> +	}
> +
> +	value = DMA_CTRL_GO | DMA_CTRL_IN | DMA_CTRL_PERF_EN |
> +		DMA_CTRL_REUSE | DMA_CTRL_IE_DONE | DMA_CTRL_IS_DONE |
> +		DMA_CTRL_BURST_8 | DMA_CTRL_EN_A;
> +	if (oob_required)
> +		value |= DMA_CTRL_EN_B;
> +	writel(value, nand->regs + DMA_CTRL);
> +
> +	value = CMD_CLE | CMD_ALE | CMD_ALE_SIZE(addrs) | CMD_SEC_CMD |
> +		CMD_RBSY_CHK | CMD_GO | CMD_RX | CMD_TRANS_SIZE(9) |
> +		CMD_A_VALID | CMD_CE(nand->cur_chip);
> +	if (oob_required)
> +		value |= CMD_B_VALID;
> +	writel(value, nand->regs + CMD);
> +
> +	wait_for_completion(&nand->command_complete);
> +	wait_for_completion(&nand->dma_complete);
> +
> +	if (oob_required) {
> +		struct mtd_oob_region oobregion;
> +
> +		mtd_ooblayout_free(mtd, 0, &oobregion);
> +		memcpy(chip->oob_poi, nand->oob_buf + oobregion.offset,
> +		       mtd_ooblayout_count_freebytes(mtd));
> +	}
> +	memcpy(buf, nand->data_buf, mtd->writesize);
> +
> +	value = readl(nand->regs + CFG);
> +	value &= ~(CFG_HW_ECC | CFG_ERR_COR);
> +	writel(value, nand->regs + CFG);
> +
> +	value = readl(nand->regs + DEC_STATUS);
> +	if (value & DEC_STATUS_A_ECC_FAIL) {
> +		/*
> +		 * The ECC isn't smart enough to figure out if a page is
> +		 * completely erased and flags an error in this case. So we
> +		 * check the read data here to figure out if it's a legitimate
> +		 * error or a false positive.
> +		 */
> +		int i, err;
> +		int flips_threshold = chip->ecc.strength / 2;
> +		int max_bitflips = 0;
> +
> +		for (i = 0; i < chip->ecc.steps; i++) {
> +			u8 *data = buf + (chip->ecc.size * i);
> +			err = nand_check_erased_ecc_chunk(data, chip->ecc.size,
> +							  NULL, 0,
> +							  NULL, 0,
> +							  flips_threshold);
> +			if (err < 0)
> +				return err;
> +
> +			max_bitflips += max_bitflips;
> +		}
> +
> +		return max_bitflips;
> +	}
> +
> +	if (nand->last_read_error) {
> +		int max_corr_cnt, corr_sec_flag;
> +
> +		value = readl(nand->regs + DEC_STAT_BUF);
> +		corr_sec_flag = (value & DEC_STAT_BUF_CORR_SEC_FLAG_MASK) >>
> +				DEC_STAT_BUF_CORR_SEC_FLAG_SHIFT;
> +		max_corr_cnt = (value & DEC_STAT_BUF_MAX_CORR_CNT_MASK) >>
> +			       DEC_STAT_BUF_MAX_CORR_CNT_SHIFT;
> +
> +		/*
> +		 * The value returned in the register is the maximum of
> +		 * bitflips encountered in any of the ECC regions. As there is
> +		 * no way to get the number of bitflips in a specific regions
> +		 * we are not able to deliver correct stats but instead
> +		 * overestimate the number of corrected bitflips by assuming
> +		 * that all regions where errors have been corrected
> +		 * encountered the maximum number of bitflips.
> +		 */
> +		mtd->ecc_stats.corrected += max_corr_cnt * hweight8(corr_sec_flag);
> +		nand->last_read_error = false;
> +		return value;
> +	}
> +
> +	return 0;
> +}
> +
> +static int tegra_nand_write_page(struct mtd_info *mtd, struct nand_chip *chip,
> +				 const uint8_t *buf, int oob_required, int page)
> +{
> +	struct tegra_nand *nand = to_tegra_nand(mtd);
> +	u32 value, addrs;
> +
> +	writel(NAND_CMD_SEQIN, nand->regs + CMD_1);
> +	writel(NAND_CMD_PAGEPROG, nand->regs + CMD_2);
> +
> +	addrs = tegra_nand_fill_address(mtd, chip, page);
> +
> +	value = readl(nand->regs + CFG);
> +	value |= CFG_HW_ECC | CFG_ERR_COR;
> +	writel(value, nand->regs + CFG);
> +
> +	memcpy(nand->data_buf, buf, mtd->writesize);
> +
> +	writel(mtd->writesize - 1, nand->regs + DMA_CFG_A);
> +	writel(nand->data_dma, nand->regs + DATA_PTR);
> +
> +	if (oob_required) {
> +		struct mtd_oob_region oobregion;
> +
> +		mtd_ooblayout_free(mtd, 0, &oobregion);
> +		memcpy(nand->oob_buf, chip->oob_poi + oobregion.offset,
> +		       mtd_ooblayout_count_freebytes(mtd));
> +		writel(mtd_ooblayout_count_freebytes(mtd) - 1,
> +		       nand->regs + DMA_CFG_B);
> +		writel(nand->oob_dma, nand->regs + TAG_PTR);
> +	} else {
> +		writel(0, nand->regs + DMA_CFG_B);
> +		writel(0, nand->regs + TAG_PTR);
> +	}
> +
> +	value = DMA_CTRL_GO | DMA_CTRL_OUT | DMA_CTRL_PERF_EN |
> +		DMA_CTRL_IE_DONE | DMA_CTRL_IS_DONE |
> +		DMA_CTRL_BURST_8 | DMA_CTRL_EN_A;
> +	if (oob_required)
> +		value |= DMA_CTRL_EN_B;
> +	writel(value, nand->regs + DMA_CTRL);
> +
> +	value = CMD_CLE | CMD_ALE | CMD_ALE_SIZE(addrs) | CMD_SEC_CMD |
> +		CMD_AFT_DAT | CMD_RBSY_CHK | CMD_GO | CMD_TX | CMD_A_VALID |
> +		CMD_TRANS_SIZE(9) | CMD_CE(nand->cur_chip);
> +	if (oob_required)
> +		value |= CMD_B_VALID;
> +	writel(value, nand->regs + CMD);
> +
> +	wait_for_completion(&nand->command_complete);
> +	wait_for_completion(&nand->dma_complete);
> +
> +	value = readl(nand->regs + CFG);
> +	value &= ~(CFG_HW_ECC | CFG_ERR_COR);
> +	writel(value, nand->regs + CFG);
> +
> +	return 0;
> +}
> +
> +static void tegra_nand_setup_timing(struct tegra_nand *nand, int mode)
> +{
> +	/*
> +	 * The period (and all other timings in this function) is in ps,
> +	 * so need to take care here to avoid integer overflows.
> +	 */
> +	unsigned int rate = clk_get_rate(nand->clk) / 1000000;
> +	unsigned int period = DIV_ROUND_UP(1000000, rate);
> +	const struct nand_sdr_timings *timings;
> +	u32 val, reg = 0;
> +
> +	timings = onfi_async_timing_mode_to_sdr_timings(mode);
> +
> +	val = DIV_ROUND_UP(max3(timings->tAR_min, timings->tRR_min,
> +				timings->tRC_min), period);
> +	if (val > 2)
> +		val -= 3;
> +	reg |= TIMING_TCR_TAR_TRR(val);
> +
> +	val = DIV_ROUND_UP(max(max(timings->tCS_min, timings->tCH_min),
> +				   max(timings->tALS_min, timings->tALH_min)),
> +			   period);
> +	if (val > 1)
> +		val -= 2;
> +	reg |= TIMING_TCS(val);
> +
> +	val = DIV_ROUND_UP(max(timings->tRP_min, timings->tREA_max) + 6000,
> +			   period);
> +	reg |= TIMING_TRP(val) | TIMING_TRP_RESP(val);
> +
> +	reg |= TIMING_TWB(DIV_ROUND_UP(timings->tWB_max, period));
> +	reg |= TIMING_TWHR(DIV_ROUND_UP(timings->tWHR_min, period));
> +	reg |= TIMING_TWH(DIV_ROUND_UP(timings->tWH_min, period));
> +	reg |= TIMING_TWP(DIV_ROUND_UP(timings->tWP_min, period));
> +	reg |= TIMING_TRH(DIV_ROUND_UP(timings->tRHW_min, period));
> +
> +	writel(reg, nand->regs + TIMING_1);
> +
> +	val = DIV_ROUND_UP(timings->tADL_min, period);
> +	if (val > 2)
> +		val -= 3;
> +	reg = TIMING_TADL(val);
> +
> +	writel(reg, nand->regs + TIMING_2);
> +}
> +
> +static void tegra_nand_setup_chiptiming(struct tegra_nand *nand)
> +{
> +	struct nand_chip *chip = &nand->chip;
> +	int mode;
> +
> +	mode = onfi_get_async_timing_mode(chip);
> +	if (mode == ONFI_TIMING_MODE_UNKNOWN)
> +		mode = chip->onfi_timing_mode_default;
> +	else
> +		mode = fls(mode);
> +
> +	tegra_nand_setup_timing(nand, mode);
> +}
> +
> +static int tegra_nand_probe(struct platform_device *pdev)
> +{
> +	struct reset_control *rst;
> +	struct tegra_nand *nand;
> +	struct nand_chip *chip;
> +	struct mtd_info *mtd;
> +	struct resource *res;
> +	unsigned long value;
> +	int irq, err = 0;
> +
> +	nand = devm_kzalloc(&pdev->dev, sizeof(*nand), GFP_KERNEL);
> +	if (!nand)
> +		return -ENOMEM;
> +
> +	nand->dev = &pdev->dev;
> +
> +	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +	nand->regs = devm_ioremap_resource(&pdev->dev, res);
> +	if (IS_ERR(nand->regs))
> +		return PTR_ERR(nand->regs);
> +
> +	irq = platform_get_irq(pdev, 0);
> +	err = devm_request_irq(&pdev->dev, irq, tegra_nand_irq, 0,
> +			       dev_name(&pdev->dev), nand);
> +	if (err)
> +		return err;
> +
> +	rst = devm_reset_control_get(&pdev->dev, "nand");
> +	if (IS_ERR(rst))
> +		return PTR_ERR(rst);
> +
> +	nand->clk = devm_clk_get(&pdev->dev, "nand");
> +	if (IS_ERR(nand->clk))
> +		return PTR_ERR(nand->clk);
> +
> +	nand->wp_gpio = gpiod_get_optional(&pdev->dev, "wp-gpios",
> +					   GPIOD_OUT_HIGH);
> +	if (IS_ERR(nand->wp_gpio))
> +		return PTR_ERR(nand->wp_gpio);
> +
> +	err = clk_prepare_enable(nand->clk);
> +	if (err)
> +		return err;
> +
> +	reset_control_assert(rst);
> +	udelay(2);
> +	reset_control_deassert(rst);
> +
> +	value = HWSTATUS_RDSTATUS_MASK(1) | HWSTATUS_RDSTATUS_VALUE(0) |
> +		HWSTATUS_RBSY_MASK(NAND_STATUS_READY) |
> +		HWSTATUS_RBSY_VALUE(NAND_STATUS_READY);
> +	writel(NAND_CMD_STATUS, nand->regs + HWSTATUS_CMD);
> +	writel(value, nand->regs + HWSTATUS_MASK);
> +
> +	init_completion(&nand->command_complete);
> +	init_completion(&nand->dma_complete);
> +
> +	/* clear interrupts */
> +	value = readl(nand->regs + ISR);
> +	writel(value, nand->regs + ISR);
> +
> +	writel(DMA_CTRL_IS_DONE, nand->regs + DMA_CTRL);
> +
> +	/* enable interrupts */
> +	value = IER_UND | IER_OVR | IER_CMD_DONE | IER_ECC_ERR | IER_GIE;
> +	writel(value, nand->regs + IER);
> +
> +	/* reset config */
> +	writel(0, nand->regs + CFG);
> +
> +	chip = &nand->chip;
> +	mtd = nand_to_mtd(chip);
> +
> +	mtd->dev.parent = &pdev->dev;
> +	mtd->name = "tegra_nand";
> +	mtd->owner = THIS_MODULE;
> +
> +	nand_set_flash_node(chip, pdev->dev.of_node);
> +	nand_set_controller_data(chip, nand);
> +
> +	chip->options = NAND_NO_SUBPAGE_WRITE;
> +	chip->exec_op = tegra_nand_exec_op;
> +	chip->select_chip = tegra_nand_select_chip;
> +	tegra_nand_setup_timing(nand, 0);
> +
> +	err = nand_scan_ident(mtd, 1, NULL);
> +	if (err)
> +		goto err_disable_clk;
> +
> +	if (chip->bbt_options & NAND_BBT_USE_FLASH)
> +		chip->bbt_options |= NAND_BBT_NO_OOB;
> +
> +	nand->data_buf = dmam_alloc_coherent(&pdev->dev, mtd->writesize,
> +					    &nand->data_dma, GFP_KERNEL);
> +	if (!nand->data_buf) {
> +		err = -ENOMEM;
> +		goto err_disable_clk;
> +	}
> +
> +	nand->oob_buf = dmam_alloc_coherent(&pdev->dev, mtd->oobsize,
> +					    &nand->oob_dma, GFP_KERNEL);
> +	if (!nand->oob_buf) {
> +		err = -ENOMEM;
> +		goto err_disable_clk;
> +	}
> +
> +	chip->ecc.mode = NAND_ECC_HW;
> +	chip->ecc.size = 512;
> +	chip->ecc.read_page = tegra_nand_read_page;
> +	chip->ecc.write_page = tegra_nand_write_page;
> +
> +	value = readl(nand->regs + CFG);
> +	value |= CFG_PIPE_EN | CFG_SKIP_SPARE | CFG_SKIP_SPARE_SIZE_4 |
> +		 CFG_TAG_BYTE_SIZE(mtd_ooblayout_count_freebytes(mtd) - 1);
> +
> +	if (chip->options & NAND_BUSWIDTH_16)
> +		value |= CFG_BUS_WIDTH_16;
> +
> +	switch (mtd->oobsize) {
> +	case 16:
> +		mtd_set_ooblayout(mtd, &tegra_nand_oob_16_ops);
> +		chip->ecc.strength = 1;
> +		chip->ecc.bytes = 4;
> +		break;
> +	case 64:
> +		mtd_set_ooblayout(mtd, &tegra_nand_oob_64_ops);
> +		chip->ecc.strength = 8;
> +		chip->ecc.bytes = 18;
> +		value |= CFG_ECC_SEL | CFG_TVAL_8;
> +		break;
> +	case 128:
> +		mtd_set_ooblayout(mtd, &tegra_nand_oob_128_ops);
> +		chip->ecc.strength = 8;
> +		chip->ecc.bytes = 18;
> +		value |= CFG_ECC_SEL | CFG_TVAL_8;
> +		break;
> +	case 224:
> +		mtd_set_ooblayout(mtd, &tegra_nand_oob_224_ops);
> +		chip->ecc.strength = 8;
> +		chip->ecc.bytes = 18;
> +		value |= CFG_ECC_SEL | CFG_TVAL_8;
> +		break;
> +	default:
> +		dev_err(&pdev->dev, "unhandled OOB size %d\n", mtd->oobsize);
> +		err = -ENODEV;
> +		goto err_disable_clk;
> +	}


This selects the algorithm used somewhat ad-hoc.


The controller supports Hamming/Reed-Solomon and BCH. I was thinking to
use the device tree property nand-ecc-algo for manual algorithm
selection (need to add rs...). Then use ONFI/JEDEC/parameter page/driver
information from ecc_strength_ds/ecc_step_ds to select an appropriate
ECC strength.

Or in case device tree nand-ecc-maximize just use the maximum possible
with given algorithm/OOB size.

Does that sound reasonable?

--
Stefan


> +
> +	switch (mtd->writesize) {
> +	case 256:
> +		value |= CFG_PS_256;
> +		break;
> +	case 512:
> +		value |= CFG_PS_512;
> +		break;
> +	case 1024:
> +		value |= CFG_PS_1024;
> +		break;
> +	case 2048:
> +		value |= CFG_PS_2048;
> +		break;
> +	case 4096:
> +		value |= CFG_PS_4096;
> +		break;
> +	default:
> +		dev_err(&pdev->dev, "unhandled writesize %d\n", mtd->writesize);
> +		err = -ENODEV;
> +		goto err_disable_clk;
> +	}
> +
> +	writel(value, nand->regs + CFG);
> +
> +	tegra_nand_setup_chiptiming(nand);
> +
> +	err = nand_scan_tail(mtd);
> +	if (err)
> +		goto err_disable_clk;
> +
> +	err = mtd_device_register(mtd, NULL, 0);
> +	if (err)
> +		goto err_cleanup_nand;
> +
> +	platform_set_drvdata(pdev, nand);
> +
> +	return 0;
> +
> +err_cleanup_nand:
> +	nand_cleanup(chip);
> +err_disable_clk:
> +	clk_disable_unprepare(nand->clk);
> +	return err;
> +}
> +
> +static int tegra_nand_remove(struct platform_device *pdev)
> +{
> +	struct tegra_nand *nand = platform_get_drvdata(pdev);
> +
> +	nand_release(nand_to_mtd(&nand->chip));
> +
> +	clk_disable_unprepare(nand->clk);
> +
> +	return 0;
> +}
> +
> +static const struct of_device_id tegra_nand_of_match[] = {
> +	{ .compatible = "nvidia,tegra20-nand" },
> +	{ /* sentinel */ }
> +};
> +
> +static struct platform_driver tegra_nand_driver = {
> +	.driver = {
> +		.name = "tegra-nand",
> +		.of_match_table = tegra_nand_of_match,
> +	},
> +	.probe = tegra_nand_probe,
> +	.remove = tegra_nand_remove,
> +};
> +module_platform_driver(tegra_nand_driver);
> +
> +MODULE_DESCRIPTION("NVIDIA Tegra NAND driver");
> +MODULE_AUTHOR("Thierry Reding <thierry.reding@nvidia.com>");
> +MODULE_AUTHOR("Lucas Stach <dev@lynxeye.de>");
> +MODULE_AUTHOR("Stefan Agner <stefan@agner.ch>");
> +MODULE_LICENSE("GPL v2");
> +MODULE_DEVICE_TABLE(of, tegra_nand_of_match);