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Date:   Sun, 12 May 2019 15:18:36 +0200
From:   Miquel Raynal <miquel.raynal@bootlin.com>
To:     Mason Yang <masonccyang@mxic.com.tw>
Cc:     broonie@kernel.org, marek.vasut@gmail.com,
        linux-kernel@vger.kernel.org, linux-spi@vger.kernel.org,
        bbrezillon@kernel.org, dwmw2@infradead.org, lee.jones@linaro.org,
        robh+dt@kernel.org, mark.rutland@arm.com,
        computersforpeace@gmail.com, paul.burton@mips.com, stefan@agner.ch,
        christophe.kerello@st.com, liang.yang@amlogic.com,
        geert@linux-m68k.org, devicetree@vger.kernel.org,
        marcel.ziswiler@toradex.com, linux-mtd@lists.infradead.org,
        richard@nod.at, juliensu@mxic.com.tw, zhengxunli@mxic.com.tw
Subject: Re: [PATCH v3 2/4] mtd: rawnand: Add Macronix MX25F0A NAND
 controller
Message-ID: <20190512151820.4f2dd9da@xps13>
In-Reply-To: <1555320234-15802-3-git-send-email-masonccyang@mxic.com.tw>
References: <1555320234-15802-1-git-send-email-masonccyang@mxic.com.tw>
        <1555320234-15802-3-git-send-email-masonccyang@mxic.com.tw>
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Hi Mason,

Mason Yang <masonccyang@mxic.com.tw> wrote on Mon, 15 Apr 2019 17:23:52
+0800:

> Add a driver for Macronix MX25F0A NAND controller.
> 
> Signed-off-by: Mason Yang <masonccyang@mxic.com.tw>
> ---
>  drivers/mtd/nand/raw/Kconfig     |   6 +
>  drivers/mtd/nand/raw/Makefile    |   1 +
>  drivers/mtd/nand/raw/mxic_nand.c | 294 +++++++++++++++++++++++++++++++++++++++
>  3 files changed, 301 insertions(+)
>  create mode 100644 drivers/mtd/nand/raw/mxic_nand.c
> 
> diff --git a/drivers/mtd/nand/raw/Kconfig b/drivers/mtd/nand/raw/Kconfig
> index e604625..e0329cc 100644
> --- a/drivers/mtd/nand/raw/Kconfig
> +++ b/drivers/mtd/nand/raw/Kconfig
> @@ -522,6 +522,12 @@ config MTD_NAND_QCOM
>  	  Enables support for NAND flash chips on SoCs containing the EBI2 NAND
>  	  controller. This controller is found on IPQ806x SoC.
>  
> +config MTD_NAND_MXIC
> +	tristate "Macronix MX25F0A NAND controller"
> +	depends on HAS_IOMEM
> +	help
> +	  This selects the Macronix MX25F0A NAND controller driver.
> +
>  config MTD_NAND_MTK
>  	tristate "Support for NAND controller on MTK SoCs"
>  	depends on ARCH_MEDIATEK || COMPILE_TEST
> diff --git a/drivers/mtd/nand/raw/Makefile b/drivers/mtd/nand/raw/Makefile
> index 5a5a72f..c8a6790 100644
> --- a/drivers/mtd/nand/raw/Makefile
> +++ b/drivers/mtd/nand/raw/Makefile
> @@ -54,6 +54,7 @@ obj-$(CONFIG_MTD_NAND_SUNXI)		+= sunxi_nand.o
>  obj-$(CONFIG_MTD_NAND_HISI504)	        += hisi504_nand.o
>  obj-$(CONFIG_MTD_NAND_BRCMNAND)		+= brcmnand/
>  obj-$(CONFIG_MTD_NAND_QCOM)		+= qcom_nandc.o
> +obj-$(CONFIG_MTD_NAND_MXIC)		+= mxic_nand.o
>  obj-$(CONFIG_MTD_NAND_MTK)		+= mtk_ecc.o mtk_nand.o
>  obj-$(CONFIG_MTD_NAND_TEGRA)		+= tegra_nand.o
>  obj-$(CONFIG_MTD_NAND_STM32_FMC2)	+= stm32_fmc2_nand.o
> diff --git a/drivers/mtd/nand/raw/mxic_nand.c b/drivers/mtd/nand/raw/mxic_nand.c
> new file mode 100644
> index 0000000..689fae2
> --- /dev/null
> +++ b/drivers/mtd/nand/raw/mxic_nand.c
> @@ -0,0 +1,294 @@
> +// SPDX-License-Identifier: GPL-2.0
> +//
> +// Copyright (C) 2019 Macronix International Co., Ltd.
> +//
> +// Authors:
> +//	Mason Yang <masonccyang@mxic.com.tw>
> +//	zhengxunli <zhengxunli@mxic.com.tw>

This is not a valid name.

Also if he appears here I suppose he should be credited in the
module_authors() macro too.

> +//

As a personal taste, I prefer when the header uses /* */ and only the
SPDX tag uses //.

> +
> +#include <linux/mfd/mxic-mx25f0a.h>
> +#include <linux/mtd/rawnand.h>
> +#include <linux/mtd/nand_ecc.h>
> +
> +#include "internals.h"
> +
> +struct mxic_nand_ctlr {
> +	struct mx25f0a_mfd *mfd;
> +	struct nand_controller base;
> +	struct nand_chip nand;

Even if this controller only supports one CS (and then, one chip),
please have a clear separation between the NAND controller and the NAND
chip by having one structure for the NAND chips and one structure for
the NAND controller.

> +};
> +
> +static void mxic_host_init(struct mxic_nand_ctlr *mxic)

Please choose a constant prefix for all functions, right now there is:
mxic_
mxic_nand_
mx25f0a_nand_

I think mxic_nand_ or mx25f0a_nand_ is wise.

> +{
> +	writel(DATA_STROB_EDO_EN, mxic->mfd->regs + DATA_STROB);
> +	writel(INT_STS_ALL, mxic->mfd->regs + INT_STS_EN);
> +	writel(0x0, mxic->mfd->regs + ONFI_DIN_CNT(0));
> +	writel(HC_CFG_NIO(8) | HC_CFG_SLV_ACT(0) | HC_CFG_IDLE_SIO_LVL(1) |
> +	       HC_CFG_TYPE(1, HC_CFG_TYPE_RAW_NAND) | HC_CFG_MAN_CS_EN,
> +	       mxic->mfd->regs + HC_CFG);
> +	writel(0x0, mxic->mfd->regs + HC_EN);
> +}
> +
> +static int  mxic_nand_wait_ready(struct nand_chip *chip)
> +{
> +	struct mxic_nand_ctlr *mxic = nand_get_controller_data(chip);
> +	u32 sts;
> +
> +	return readl_poll_timeout(mxic->mfd->regs + INT_STS, sts,
> +				  sts & INT_RDY_PIN, 0, USEC_PER_SEC);
> +}
> +
> +static void mxic_nand_select_chip(struct nand_chip *chip, int chipnr)

_select_target() is preferred now

> +{
> +	struct mxic_nand_ctlr *mxic = nand_get_controller_data(chip);
> +
> +	switch (chipnr) {
> +	case 0:
> +	case 1:
> +		writel(HC_EN_BIT, mxic->mfd->regs + HC_EN);
> +		writel(HC_CFG_MAN_CS_ASSERT | readl(mxic->mfd->regs + HC_CFG),
> +		       mxic->mfd->regs + HC_CFG);

In both case I would prefer a:

        reg = readl(...);
        reg &= ~xxx;
	reg |= yyy;
	writel(reg, ...);

Much easier to read.

> +		break;
> +
> +	case -1:
> +		writel(~HC_CFG_MAN_CS_ASSERT & readl(mxic->mfd->regs + HC_CFG),
> +		       mxic->mfd->regs + HC_CFG);
> +		writel(0, mxic->mfd->regs + HC_EN);
> +		break;
> +
> +	default:

Error?

> +		break;
> +	}
> +}
> +
> +static int mxic_nand_data_xfer(struct mxic_nand_ctlr *mxic, const void *txbuf,
> +			       void *rxbuf, unsigned int len)
> +{

There is not so much code shared, why not separating this function for
rx and tx cases?

> +	unsigned int pos = 0;
> +
> +	while (pos < len) {
> +		unsigned int nbytes = len - pos;
> +		u32 data = 0xffffffff;
> +		u32 sts;
> +		int ret;
> +
> +		if (nbytes > 4)
> +			nbytes = 4;
> +
> +		if (txbuf)
> +			memcpy(&data, txbuf + pos, nbytes);
> +
> +		ret = readl_poll_timeout(mxic->mfd->regs + INT_STS, sts,
> +					 sts & INT_TX_EMPTY, 0, USEC_PER_SEC);

Using USEC_PER_SEC for a delay is weird

> +		if (ret)
> +			return ret;
> +
> +		writel(data, mxic->mfd->regs + TXD(nbytes % 4));
> +
> +		if (rxbuf) {
> +			ret = readl_poll_timeout(mxic->mfd->regs + INT_STS, sts,
> +						 sts & INT_TX_EMPTY, 0,
> +						 USEC_PER_SEC);
> +			if (ret)
> +				return ret;
> +
> +			ret = readl_poll_timeout(mxic->mfd->regs + INT_STS, sts,
> +						 sts & INT_RX_NOT_EMPTY, 0,
> +						 USEC_PER_SEC);
> +			if (ret)
> +				return ret;
> +
> +			data = readl(mxic->mfd->regs + RXD);
> +			data >>= (8 * (4 - nbytes));

What is this? Are you trying to handle some endianness issue?

> +			memcpy(rxbuf + pos, &data, nbytes);
> +			WARN_ON(readl(mxic->mfd->regs + INT_STS) &
> +				INT_RX_NOT_EMPTY);
> +		} else {
> +			readl(mxic->mfd->regs + RXD);
> +		}
> +		WARN_ON(readl(mxic->mfd->regs + INT_STS) & INT_RX_NOT_EMPTY);
> +
> +		pos += nbytes;
> +	}
> +
> +	return 0;
> +}
> +
> +static int mxic_nand_exec_op(struct nand_chip *chip,
> +			     const struct nand_operation *op, bool check_only)
> +{
> +	struct mxic_nand_ctlr *mxic = nand_get_controller_data(chip);
> +	const struct nand_op_instr *instr = NULL;
> +	int i, len = 0, ret = 0;
> +	unsigned int op_id;
> +	unsigned char cmdcnt = 0, addr_cnt = 0, cmd_addr[8] = {0};
> +
> +	for (op_id = 0; op_id < op->ninstrs; op_id++) {
> +		instr = &op->instrs[op_id];
> +
> +		switch (instr->type) {
> +		case NAND_OP_CMD_INSTR:
> +			cmd_addr[len++] = instr->ctx.cmd.opcode;
> +			cmdcnt++;
> +			break;
> +
> +		case NAND_OP_ADDR_INSTR:
> +			for (i = 0; i < instr->ctx.addr.naddrs; i++)
> +				cmd_addr[len++] = instr->ctx.addr.addrs[i];
> +			addr_cnt = i;
> +			break;
> +
> +		case NAND_OP_DATA_IN_INSTR:
> +			break;
> +
> +		case NAND_OP_DATA_OUT_INSTR:
> +			writel(instr->ctx.data.len,
> +			       mxic->mfd->regs + ONFI_DIN_CNT(0));
> +			break;
> +
> +		case NAND_OP_WAITRDY_INSTR:
> +			break;
> +		}
> +	}
> +
> +	if (op_id == 5 && instr->type == NAND_OP_WAITRDY_INSTR) {
> +		/*
> +		 * In case cmd-addr-data-cmd-wait in a sequence,
> +		 * separate the 2'nd command, i.e,. nand_prog_page_op()
> +		 */

I think this is the kind of limitation that could be described very
easily with a nand_op_parser structure and used by
nand_op_parser_exec_op() (see marvell_nand.c).

> +		writel(OP_CMD_BUSW(OP_BUSW_8) | OP_ADDR_BUSW(OP_BUSW_8) |
> +		       OP_DATA_BUSW(OP_BUSW_8) | OP_DUMMY_CYC(0x3F) |
> +		       OP_ADDR_BYTES(addr_cnt) |
> +		       OP_CMD_BYTES(1), mxic->mfd->regs + SS_CTRL(0));
> +		writel(0, mxic->mfd->regs + HC_EN);
> +		writel(HC_EN_BIT, mxic->mfd->regs + HC_EN);
> +
> +		mxic_nand_data_xfer(mxic, cmd_addr, NULL, len - 1);
> +
> +		mxic_nand_data_xfer(mxic, instr->ctx.data.buf.out, NULL,
> +				    instr->ctx.data.len);
> +
> +		writel(0, mxic->mfd->regs + HC_EN);
> +		writel(HC_EN_BIT, mxic->mfd->regs + HC_EN);
> +		mxic_nand_data_xfer(mxic, &cmd_addr[--len], NULL, 1);
> +		ret = mxic_nand_wait_ready(chip);
> +		if (ret)
> +			goto err_out;
> +		return ret;
> +	}
> +
> +	if (len) {
> +		writel(OP_CMD_BUSW(OP_BUSW_8) | OP_ADDR_BUSW(OP_BUSW_8) |
> +		       OP_DATA_BUSW(OP_BUSW_8) | OP_DUMMY_CYC(0x3F) |
> +		       OP_ADDR_BYTES(addr_cnt) |
> +		       OP_CMD_BYTES(cmdcnt > 0 ? cmdcnt : 0),
> +		       mxic->mfd->regs + SS_CTRL(0));
> +		writel(0, mxic->mfd->regs + HC_EN);
> +		writel(HC_EN_BIT, mxic->mfd->regs + HC_EN);
> +
> +		mxic_nand_data_xfer(mxic, cmd_addr, NULL, len);
> +	}
> +
> +	for (op_id = 0; op_id < op->ninstrs; op_id++) {
> +		instr = &op->instrs[op_id];
> +
> +		switch (instr->type) {
> +		case NAND_OP_CMD_INSTR:
> +		case NAND_OP_ADDR_INSTR:
> +			break;
> +
> +		case NAND_OP_DATA_IN_INSTR:
> +			writel(0x0, mxic->mfd->regs + ONFI_DIN_CNT(0));
> +			writel(readl(mxic->mfd->regs + SS_CTRL(0)) | OP_READ,
> +			       mxic->mfd->regs + SS_CTRL(0));
> +			mxic_nand_data_xfer(mxic, NULL, instr->ctx.data.buf.in,
> +					    instr->ctx.data.len);
> +			break;
> +
> +		case NAND_OP_DATA_OUT_INSTR:
> +			mxic_nand_data_xfer(mxic, instr->ctx.data.buf.out, NULL,
> +					    instr->ctx.data.len);
> +			break;
> +
> +		case NAND_OP_WAITRDY_INSTR:
> +			ret = mxic_nand_wait_ready(chip);
> +			if (ret)
> +				goto err_out;
> +			break;
> +		}
> +	}
> +
> +err_out:
> +	return ret;

Ditto, please return directly if there is nothing in the error path.

> +}
> +
> +static const struct nand_controller_ops mxic_nand_controller_ops = {
> +	.exec_op = mxic_nand_exec_op,
> +};
> +
> +static int mx25f0a_nand_probe(struct platform_device *pdev)
> +{
> +	struct mtd_info *mtd;
> +	struct mx25f0a_mfd *mfd = dev_get_drvdata(pdev->dev.parent);
> +	struct mxic_nand_ctlr *mxic;
> +	struct nand_chip *nand_chip;
> +	int err;
> +
> +	mxic = devm_kzalloc(&pdev->dev, sizeof(struct mxic_nand_ctlr),
> +			    GFP_KERNEL);

mxic for a NAND controller structure is probably not a name meaningful
enough.

> +	if (!mxic)
> +		return -ENOMEM;
> +
> +	nand_chip = &mxic->nand;
> +	mtd = nand_to_mtd(nand_chip);
> +	mtd->dev.parent = pdev->dev.parent;
> +	nand_chip->ecc.priv = NULL;
> +	nand_set_flash_node(nand_chip, pdev->dev.parent->of_node);
> +	nand_chip->priv = mxic;
> +
> +	mxic->mfd = mfd;
> +
> +	nand_chip->legacy.select_chip = mxic_nand_select_chip;

Please don't implement legacy interfaces. You can check in
marvell_nand.c how this is handled now:

b25251414f6e mtd: rawnand: marvell: Stop implementing ->select_chip()

> +	mxic->base.ops = &mxic_nand_controller_ops;
> +	nand_controller_init(&mxic->base);
> +	nand_chip->controller = &mxic->base;
> +
> +	mxic_host_init(mxic);
> +
> +	err = nand_scan(nand_chip, 1);
> +	if (err)
> +		goto fail;

You can return directly as there is nothing to clean in the error path.

> +
> +	err = mtd_device_register(mtd, NULL, 0);
> +	if (err)
> +		goto fail;

Ditto

> +
> +	platform_set_drvdata(pdev, mxic);
> +
> +	return 0;
> +fail:
> +	return err;
> +}
> +
> +static int mx25f0a_nand_remove(struct platform_device *pdev)
> +{
> +	struct mxic_nand_ctlr *mxic = platform_get_drvdata(pdev);
> +
> +	nand_release(&mxic->nand);
> +
> +	return 0;
> +}
> +
> +static struct platform_driver mx25f0a_nand_driver = {
> +	.probe		= mx25f0a_nand_probe,

Please don't align '=' on tabs.

> +	.remove		= mx25f0a_nand_remove,
> +	.driver		= {
> +		.name	= "mxic-nand-ctlr",
> +	},
> +};
> +module_platform_driver(mx25f0a_nand_driver);

mx25f0a_nand_controller_driver would be better

> +
> +MODULE_AUTHOR("Mason Yang <masonccyang@mxic.com.tw>");
> +MODULE_DESCRIPTION("MX25F0A RAW NAND controller driver");
> +MODULE_LICENSE("GPL v2");

Thanks,
Miquèl