Re: [PATCH v1 2/5] mtd: spinand: add OTP support

[Miquel Raynal]

Hi Martin,

mmkurbanov@xxxxxxxxxxxxxxxxx wrote on Mon, 17 Jun 2024 16:34:54 +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().

Good job! Please find minor comments below.

> 
> Signed-off-by: Martin Kurbanov <mmkurbanov@xxxxxxxxxxxxxxxxx>
> ---
>  drivers/mtd/nand/spi/Makefile |   3 +-
>  drivers/mtd/nand/spi/core.c   |   3 +
>  drivers/mtd/nand/spi/otp.c    | 219 ++++++++++++++++++++++++++++++++++
>  include/linux/mtd/spinand.h   |  56 +++++++++
>  4 files changed, 280 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..e1f96b1898dcb
> --- /dev/null
> +++ b/drivers/mtd/nand/spi/otp.c
> @@ -0,0 +1,219 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (c) 2024, SaluteDevices. All Rights Reserved.
> + *
> + * Author: Martin Kurbanov <mmkurbanov@xxxxxxxxxxxxxxxxx>
> + */
> +
> +#include <linux/mtd/mtd.h>
> +#include <linux/mtd/spinand.h>
> +
> +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->layout.npages * otp_pagesize;
> +}
> +
> +static unsigned int spinand_otp_npages(const struct spinand_device *spinand)
> +{
> +	return spinand->otp->layout.npages;

Maybe you can move this helper up and use it in spinand_otp_size().

> +}
> +

...

> +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;
> +	size_t total_len = len;
> +	int ret;
> +
> +	if (ofs < 0 || ofs + len > spinand_otp_size(spinand))
> +		return -EINVAL;
> +

Please just check if (!len) here

> +	total_len = min_t(size_t, total_len, spinand_otp_size(spinand) - ofs);

                                  len ^^^

Here you can just compute the minimum and don't check the output. It
will be simpler to understand.

> +	if (!total_len)
> +		return 0;
> +
> +	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)) {
> +		WARN(1, "Can not disable OTP mode\n");

Please avoid WARN() statements like that. A normal pr_warn is enough.

> +		ret = -EIO;
> +	}
> +
> +out_unlock:
> +	mutex_unlock(&spinand->lock);
> +	return ret;
> +}
> +
> +static int spinand_mtd_otp_read(struct mtd_info *mtd, loff_t from, size_t len,

Can you keep the naming consistent?                 ofs vs. from  ^

> +				size_t *retlen, u8 *buf)
> +{
> +	return spinand_mtd_otp_rw(mtd, from, len, retlen, buf, false);
> +}
> +
> +static int spinand_mtd_otp_write(struct mtd_info *mtd, loff_t to, size_t len,
> +				 size_t *retlen, const u8 *buf)
> +{
> +	return spinand_mtd_otp_rw(mtd, to, len, retlen, (u8 *)buf, true);
> +}
> +
> +static int spinand_mtd_otp_erase(struct mtd_info *mtd, loff_t from, 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;

This check seems sensible but is absent in the other helpers. Any
reason? Please add it to _lock() and _rw()

> +
> +	if (from < 0 || (from + len) > spinand_otp_size(spinand))
> +		return -EINVAL;

And this is also repeated three times, it is probably worth factorizing
out.

> +
> +	mutex_lock(&spinand->lock);
> +	ret = ops->erase(spinand, from, len);
> +	mutex_unlock(&spinand->lock);
> +
> +	return ret;
> +}
> +
> +static int spinand_mtd_otp_lock(struct mtd_info *mtd, loff_t from, 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 (from < 0 || (from + len) > spinand_otp_size(spinand))
> +		return -EINVAL;
> +
> +	mutex_lock(&spinand->lock);
> +	ret = ops->lock(spinand, from, 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)
> +		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..a0d42a9be333f 100644
> --- a/include/linux/mtd/spinand.h
> +++ b/include/linux/mtd/spinand.h
> @@ -322,6 +322,43 @@ struct spinand_ondie_ecc_conf {
>  	u8 status;
>  };
>  
> +/**
> + * struct spinand_otp_layout - structure to describe the SPI NAND OTP area
> + * @npages: number of pages in the OTP
> + */
> +struct spinand_otp_layout {
> +	unsigned int npages;
> +};
> +
> +/**
> + * struct spinand_otp_ops - SPI NAND OTP methods
> + * @info: Get the OTP area information
> + * @lock: lock an OTP region
> + * @erase: erase an OTP region
> + * @read: read from the SPI NAND OTP area
> + * @write: write to the SPI NAND OTP area
> + */
> +struct spinand_otp_ops {
> +	int (*info)(struct spinand_device *spinand, size_t len,
> +		    struct otp_info *buf, size_t *retlen);
> +	int (*lock)(struct spinand_device *spinand, loff_t from, size_t len);
> +	int (*erase)(struct spinand_device *spinand, loff_t from, size_t len);
> +	int (*read)(struct spinand_device *spinand, loff_t from, size_t len,
> +		    u8 *buf, size_t *retlen);
> +	int (*write)(struct spinand_device *spinand, loff_t from, size_t len,
> +		     const u8 *buf, size_t *retlen);
> +};
> +
> +/**
> + * struct spinand_otp - SPI NAND OTP grouping structure
> + * @layout: OTP region layout
> + * @ops: OTP access ops
> + */
> +struct spinand_otp {
> +	const struct spinand_otp_layout layout;
> +	const struct spinand_otp_ops *ops;
> +};
> +
>  /**
>   * struct spinand_info - Structure used to describe SPI NAND chips
>   * @model: model name
> @@ -354,6 +391,7 @@ struct spinand_info {
>  	} op_variants;
>  	int (*select_target)(struct spinand_device *spinand,
>  			     unsigned int target);
> +	struct spinand_otp otp;
>  };
>  
>  #define SPINAND_ID(__method, ...)					\
> @@ -379,6 +417,14 @@ struct spinand_info {
>  #define SPINAND_SELECT_TARGET(__func)					\
>  	.select_target = __func,
>  
> +#define SPINAND_OTP_INFO(__npages, __ops)				\
> +	.otp = {							\
> +		.layout = {						\
> +			.npages = __npages,				\
> +		},							\
> +		.ops = __ops,						\
> +	}
> +
>  #define SPINAND_INFO(__model, __id, __memorg, __eccreq, __op_variants,	\
>  		     __flags, ...)					\
>  	{								\
> @@ -422,6 +468,7 @@ struct spinand_dirmap {
>   *		passed in spi_mem_op be DMA-able, so we can't based the bufs on
>   *		the stack
>   * @manufacturer: SPI NAND manufacturer information
> + * @otp: SPI NAND OTP info.
>   * @priv: manufacturer private data
>   */
>  struct spinand_device {
> @@ -450,6 +497,7 @@ struct spinand_device {
>  	u8 *oobbuf;
>  	u8 *scratchbuf;
>  	const struct spinand_manufacturer *manufacturer;
> +	const struct spinand_otp *otp;
>  	void *priv;
>  };
>  
> @@ -525,4 +573,12 @@ int spinand_read_page(struct spinand_device *spinand,
>  int spinand_write_page(struct spinand_device *spinand,
>  		       const struct nand_page_io_req *req);
>  
> +void spinand_set_mtd_otp_ops(struct spinand_device *spinand);
> +
> +int spinand_otp_read(struct spinand_device *spinand, loff_t from, size_t len,
> +		     u8 *buf, size_t *retlen);
> +
> +int spinand_otp_write(struct spinand_device *spinand, loff_t from, size_t len,
> +		      const u8 *buf, size_t *retlen);
> +

Why exposing spinand_otp_read and spinand_otp_write ?

>  #endif /* __LINUX_MTD_SPINAND_H */


Thanks,
Miquèl