Re: [PATCH v2 2/5] mtd: spinand: add OTP support

[Miquel Raynal <miquel.raynal@bootlin.com>]

Hi Martin,

mmkurbanov@salutedevices.com wrote on Tue, 27 Aug 2024 20:49:00 +0300:

> The MTD subsystem already supports accessing two OTP areas: user and
> factory. User areas can be written by the user. This patch only adds
> support for the user areas.
> 
> In this patch the OTP_INFO macro is provided to add parameters to
> spinand_info.
> To implement OTP operations, the client (flash driver) is provided with
> 5 callbacks: .read(), .write(), .info(), .lock(), .erase().

Overall this looks good, I have minor changes to request. I'm not yet
done down to the last patch, but I think the implementation is neat.

> Signed-off-by: Martin Kurbanov <mmkurbanov@salutedevices.com>
> ---
>  drivers/mtd/nand/spi/Makefile |   3 +-
>  drivers/mtd/nand/spi/core.c   |   3 +
>  drivers/mtd/nand/spi/otp.c    | 232 ++++++++++++++++++++++++++++++++++
>  include/linux/mtd/spinand.h   |  56 ++++++++
>  4 files changed, 293 insertions(+), 1 deletion(-)
>  create mode 100644 drivers/mtd/nand/spi/otp.c
> 
> diff --git a/drivers/mtd/nand/spi/Makefile b/drivers/mtd/nand/spi/Makefile
> index 19cc77288ebbc..60d2e830ffc6b 100644
> --- a/drivers/mtd/nand/spi/Makefile
> +++ b/drivers/mtd/nand/spi/Makefile
> @@ -1,4 +1,5 @@
>  # SPDX-License-Identifier: GPL-2.0
> -spinand-objs := core.o alliancememory.o ato.o esmt.o foresee.o gigadevice.o macronix.o
> +spinand-objs := core.o otp.o
> +spinand-objs += alliancememory.o ato.o esmt.o foresee.o gigadevice.o macronix.o
>  spinand-objs += micron.o paragon.o toshiba.o winbond.o xtx.o
>  obj-$(CONFIG_MTD_SPI_NAND) += spinand.o
> diff --git a/drivers/mtd/nand/spi/core.c b/drivers/mtd/nand/spi/core.c
> index 807c24b0c7c4f..2cb825edd49d0 100644
> --- a/drivers/mtd/nand/spi/core.c
> +++ b/drivers/mtd/nand/spi/core.c
> @@ -1111,6 +1111,7 @@ int spinand_match_and_init(struct spinand_device *spinand,
>  		spinand->flags = table[i].flags;
>  		spinand->id.len = 1 + table[i].devid.len;
>  		spinand->select_target = table[i].select_target;
> +		spinand->otp = &table[i].otp;
>  
>  		op = spinand_select_op_variant(spinand,
>  					       info->op_variants.read_cache);
> @@ -1292,6 +1293,8 @@ static int spinand_init(struct spinand_device *spinand)
>  	mtd->_max_bad_blocks = nanddev_mtd_max_bad_blocks;
>  	mtd->_resume = spinand_mtd_resume;
>  
> +	spinand_set_mtd_otp_ops(spinand);
> +
>  	if (nand->ecc.engine) {
>  		ret = mtd_ooblayout_count_freebytes(mtd);
>  		if (ret < 0)
> diff --git a/drivers/mtd/nand/spi/otp.c b/drivers/mtd/nand/spi/otp.c
> new file mode 100644
> index 0000000000000..d459f811f9c04
> --- /dev/null
> +++ b/drivers/mtd/nand/spi/otp.c
> @@ -0,0 +1,232 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (c) 2024, SaluteDevices. All Rights Reserved.
> + *
> + * Author: Martin Kurbanov <mmkurbanov@salutedevices.com>
> + */
> +
> +#include <linux/mtd/mtd.h>
> +#include <linux/mtd/spinand.h>
> +
> +static unsigned int spinand_otp_npages(const struct spinand_device *spinand)
> +{
> +	return spinand->otp->layout.npages;
> +}
> +
> +static size_t spinand_otp_size(struct spinand_device *spinand)
> +{
> +	struct nand_device *nand = spinand_to_nand(spinand);
> +	size_t otp_pagesize = nanddev_page_size(nand) +
> +			      nanddev_per_page_oobsize(nand);
> +
> +	return spinand_otp_npages(spinand) * otp_pagesize;
> +}
> +
> +static int spinand_otp_rw(struct spinand_device *spinand, loff_t ofs,
> +			  size_t len, u8 *buf, size_t *retlen, bool is_write)
> +{
> +	struct nand_device *nand = spinand_to_nand(spinand);
> +	struct nand_page_io_req req = { 0 };

					= {}; is enough

> +	unsigned long long page;
> +	size_t copied = 0;
> +	size_t otp_pagesize = nanddev_page_size(nand) +
> +			      nanddev_per_page_oobsize(nand);
> +	int ret = 0;
> +
> +	page = ofs;
> +	req.dataoffs = do_div(page, otp_pagesize);
> +	req.pos.page = page;
> +	req.type = is_write ? NAND_PAGE_WRITE : NAND_PAGE_READ;
> +	req.mode = MTD_OPS_RAW;
> +	req.databuf.in = buf;
> +
> +	while (copied < len && req.pos.page < spinand_otp_npages(spinand)) {
> +		req.datalen = min_t(unsigned int,
> +				    otp_pagesize - req.dataoffs,
> +				    len - copied);
> +
> +		if (is_write)
> +			ret = spinand_write_page(spinand, &req);
> +		else
> +			ret = spinand_read_page(spinand, &req);
> +
> +		if (ret < 0)
> +			break;
> +
> +		req.dataoffs = 0;
> +		copied += req.datalen;
> +		req.pos.page++;
> +	}
> +
> +	*retlen = copied;
> +
> +	return ret;
> +}
> +
> +/**
> + * spinand_otp_read() - Read from OTP area
> + * @spinand: the spinand device
> + * @ofs: the offset to read
> + * @len: the number of data bytes to read
> + * @buf: the buffer to store the read data
> + * @retlen: the pointer to variable to store the number of read bytes
> + *
> + * Return: 0 on success, an error code otherwise.
> + */
> +int spinand_otp_read(struct spinand_device *spinand, loff_t ofs, size_t len,
> +		     u8 *buf, size_t *retlen)
> +{
> +	return spinand_otp_rw(spinand, ofs, len, buf, retlen, false);
> +}
> +
> +/**
> + * spinand_otp_write() - Write to OTP area
> + * @spinand:  the spinand device
> + * @ofs: the offset to write to
> + * @len: the number of bytes to write
> + * @buf: the buffer with data to write
> + * @retlen: the pointer to variable to store the number of written bytes
> + *
> + * Return: 0 on success, an error code otherwise.
> + */
> +int spinand_otp_write(struct spinand_device *spinand, loff_t ofs, size_t len,
> +		      const u8 *buf, size_t *retlen)
> +{
> +	return spinand_otp_rw(spinand, ofs, len, (u8 *)buf, retlen, true);
> +}

These spinand_otp_xxx() helpers are not yet used, and thus should be
introduced later, when they are useful.

> +
> +static int spinand_otp_check_bounds(struct spinand_device *spinand, loff_t ofs,
> +				    size_t len)
> +{
> +	if (ofs < 0 || ofs + len > spinand_otp_size(spinand))
> +		return -EINVAL;
> +
> +	return 0;
> +}
> +
> +static int spinand_mtd_otp_info(struct mtd_info *mtd, size_t len,
> +				size_t *retlen, struct otp_info *buf)
> +{
> +	struct spinand_device *spinand = mtd_to_spinand(mtd);
> +	const struct spinand_otp_ops *ops = spinand->otp->ops;
> +	int ret;
> +
> +	mutex_lock(&spinand->lock);
> +	ret = ops->info(spinand, len, buf, retlen);
> +	mutex_unlock(&spinand->lock);
> +
> +	return ret;
> +}
> +
> +static int spinand_mtd_otp_rw(struct mtd_info *mtd, loff_t ofs, size_t len,
> +			      size_t *retlen, u8 *buf, bool is_write)
> +{
> +	struct spinand_device *spinand = mtd_to_spinand(mtd);
> +	const struct spinand_otp_ops *ops = spinand->otp->ops;
> +	int ret;
> +
> +	if (!len)
> +		return 0;
> +
> +	ret = spinand_otp_check_bounds(spinand, ofs, len);
> +	if (ret)
> +		return ret;
> +
> +	mutex_lock(&spinand->lock);
> +
> +	ret = spinand_upd_cfg(spinand, CFG_OTP_ENABLE, CFG_OTP_ENABLE);
> +	if (ret)
> +		goto out_unlock;
> +
> +	if (is_write)
> +		ret = ops->write(spinand, ofs, len, buf, retlen);
> +	else
> +		ret = ops->read(spinand, ofs, len, buf, retlen);
> +
> +	if (spinand_upd_cfg(spinand, CFG_OTP_ENABLE, 0)) {
> +		pr_warn(1, "Can not disable OTP mode\n");

dev_warn?

> +		ret = -EIO;
> +	}
> +
> +out_unlock:
> +	mutex_unlock(&spinand->lock);
> +	return ret;
> +}
> +
> +static int spinand_mtd_otp_read(struct mtd_info *mtd, loff_t ofs, size_t len,
> +				size_t *retlen, u8 *buf)
> +{
> +	return spinand_mtd_otp_rw(mtd, ofs, len, retlen, buf, false);
> +}
> +
> +static int spinand_mtd_otp_write(struct mtd_info *mtd, loff_t ofs, size_t len,
> +				 size_t *retlen, const u8 *buf)
> +{
> +	return spinand_mtd_otp_rw(mtd, ofs, len, retlen, (u8 *)buf, true);
> +}
> +
> +static int spinand_mtd_otp_erase(struct mtd_info *mtd, loff_t ofs, size_t len)
> +{
> +	struct spinand_device *spinand = mtd_to_spinand(mtd);
> +	const struct spinand_otp_ops *ops = spinand->otp->ops;
> +	int ret;
> +
> +	if (!ops->erase)
> +		return -EOPNOTSUPP;
> +
> +	if (!len)
> +		return 0;
> +
> +	ret = spinand_otp_check_bounds(spinand, ofs, len);
> +	if (ret)
> +		return ret;
> +
> +	mutex_lock(&spinand->lock);
> +	ret = ops->erase(spinand, ofs, len);
> +	mutex_unlock(&spinand->lock);
> +
> +	return ret;
> +}
> +
> +static int spinand_mtd_otp_lock(struct mtd_info *mtd, loff_t ofs, size_t len)
> +{
> +	struct spinand_device *spinand = mtd_to_spinand(mtd);
> +	const struct spinand_otp_ops *ops = spinand->otp->ops;
> +	int ret;
> +
> +	if (!ops->lock)
> +		return -EOPNOTSUPP;
> +
> +	if (!len)
> +		return 0;
> +
> +	ret = spinand_otp_check_bounds(spinand, ofs, len);
> +	if (ret)
> +		return ret;
> +
> +	mutex_lock(&spinand->lock);
> +	ret = ops->lock(spinand, ofs, len);
> +	mutex_unlock(&spinand->lock);
> +
> +	return ret;
> +}
> +
> +/**
> + * spinand_set_mtd_otp_ops() - Set up OTP methods
> + * @spinand: the spinand device
> + *
> + * Set up OTP methods.
> + */
> +void spinand_set_mtd_otp_ops(struct spinand_device *spinand)
> +{
> +	struct mtd_info *mtd = spinand_to_mtd(spinand);
> +
> +	if (!spinand->otp->ops)

Could we use something else as check? It feels odd to check for otp ops
and then just ignore the fact that they are here. Maybe check npages or
otp_size() ?

> +		return;
> +
> +	mtd->_get_user_prot_info = spinand_mtd_otp_info;
> +	mtd->_read_user_prot_reg = spinand_mtd_otp_read;
> +	mtd->_write_user_prot_reg = spinand_mtd_otp_write;
> +	mtd->_lock_user_prot_reg = spinand_mtd_otp_lock;
> +	mtd->_erase_user_prot_reg = spinand_mtd_otp_erase;
> +}
> diff --git a/include/linux/mtd/spinand.h b/include/linux/mtd/spinand.h
> index 555846517faf6..8099f35f0e051 100644
> --- a/include/linux/mtd/spinand.h
> +++ b/include/linux/mtd/spinand.h
> @@ -322,6 +322,43 @@ struct spinand_ondie_ecc_conf {
>  	u8 status;
>  };

Thanks,
Miquèl