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Date:   Wed, 20 Oct 2021 10:57:43 +0200
From:   Boris Brezillon <boris.brezillon@collabora.com>
To:     Sean Nyekjaer <sean@geanix.com>
Cc:     Miquel Raynal <miquel.raynal@bootlin.com>,
        Richard Weinberger <richard@nod.at>,
        Vignesh Raghavendra <vigneshr@ti.com>,
        Boris Brezillon <bbrezillon@kernel.org>,
        linux-mtd@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 3/4] mtd: rawnand: remove suspended check
Message-ID: <20211020105743.225d97f4@collabora.com>
In-Reply-To: <20211020084534.2472305-4-sean@geanix.com>
References: <20211020084534.2472305-1-sean@geanix.com>
        <20211020084534.2472305-4-sean@geanix.com>
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On Wed, 20 Oct 2021 10:45:33 +0200
Sean Nyekjaer <sean@geanix.com> wrote:

> Access is protected in upper MTD layer when MTD devices are suspended.

I think it deserves more explanation.

> 
> Fixes: 013e6292aaf5 ("mtd: rawnand: Simplify the locking")

This patch doesn't fix anything, things have been fixed in 'mtd: core:
protect access to MTD devices while in suspend'. It's just a cleanup on
top of it.

> Reviewed-by: Miquel Raynal <miquel.raynal@bootlin.com>
> Signed-off-by: Sean Nyekjaer <sean@geanix.com>
> ---
>  drivers/mtd/nand/raw/nand_base.c | 52 ++++++++------------------------
>  include/linux/mtd/rawnand.h      |  5 +--
>  2 files changed, 14 insertions(+), 43 deletions(-)
> 
> diff --git a/drivers/mtd/nand/raw/nand_base.c b/drivers/mtd/nand/raw/nand_base.c
> index 3d6c6e880520..aa2874ae3c4a 100644
> --- a/drivers/mtd/nand/raw/nand_base.c
> +++ b/drivers/mtd/nand/raw/nand_base.c
> @@ -332,19 +332,11 @@ static int nand_isbad_bbm(struct nand_chip *chip, loff_t ofs)
>   * @chip: NAND chip structure
>   *
>   * Lock the device and its controller for exclusive access
> - *
> - * Return: -EBUSY if the chip has been suspended, 0 otherwise
>   */
> -static int nand_get_device(struct nand_chip *chip)
> +static void nand_get_device(struct nand_chip *chip)
>  {
>  	mutex_lock(&chip->lock);
> -	if (chip->suspended) {
> -		mutex_unlock(&chip->lock);
> -		return -EBUSY;
> -	}
>  	mutex_lock(&chip->controller->lock);
> -
> -	return 0;
>  }
>  
>  /**
> @@ -573,10 +565,7 @@ static int nand_block_markbad_lowlevel(struct nand_chip *chip, loff_t ofs)
>  		nand_erase_nand(chip, &einfo, 0);
>  
>  		/* Write bad block marker to OOB */
> -		ret = nand_get_device(chip);
> -		if (ret)
> -			return ret;
> -
> +		nand_get_device(chip);
>  		ret = nand_markbad_bbm(chip, ofs);
>  		nand_release_device(chip);
>  	}
> @@ -3756,9 +3745,7 @@ static int nand_read_oob(struct mtd_info *mtd, loff_t from,
>  	    ops->mode != MTD_OPS_RAW)
>  		return -ENOTSUPP;
>  
> -	ret = nand_get_device(chip);
> -	if (ret)
> -		return ret;
> +	nand_get_device(chip);
>  
>  	if (!ops->datbuf)
>  		ret = nand_do_read_oob(chip, from, ops);
> @@ -4345,13 +4332,11 @@ static int nand_write_oob(struct mtd_info *mtd, loff_t to,
>  			  struct mtd_oob_ops *ops)
>  {
>  	struct nand_chip *chip = mtd_to_nand(mtd);
> -	int ret;
> +	int ret = 0;
>  
>  	ops->retlen = 0;
>  
> -	ret = nand_get_device(chip);
> -	if (ret)
> -		return ret;
> +	nand_get_device(chip);
>  
>  	switch (ops->mode) {
>  	case MTD_OPS_PLACE_OOB:
> @@ -4410,10 +4395,8 @@ int nand_erase_nand(struct nand_chip *chip, struct erase_info *instr,
>  	if (nand_region_is_secured(chip, instr->addr, instr->len))
>  		return -EIO;
>  
> -	/* Grab the lock and see if the device is available */
> -	ret = nand_get_device(chip);
> -	if (ret)
> -		return ret;
> +	/* Grab the lock */
> +	nand_get_device(chip);
>  
>  	/* Shift to get first page */
>  	page = (int)(instr->addr >> chip->page_shift);
> @@ -4499,8 +4482,8 @@ static void nand_sync(struct mtd_info *mtd)
>  
>  	pr_debug("%s: called\n", __func__);
>  
> -	/* Grab the lock and see if the device is available */
> -	WARN_ON(nand_get_device(chip));
> +	/* Grab the lock */
> +	nand_get_device(chip);
>  	/* Release it and go back */
>  	nand_release_device(chip);
>  }
> @@ -4517,9 +4500,7 @@ static int nand_block_isbad(struct mtd_info *mtd, loff_t offs)
>  	int ret;
>  
>  	/* Select the NAND device */
> -	ret = nand_get_device(chip);
> -	if (ret)
> -		return ret;
> +	nand_get_device(chip);
>  
>  	nand_select_target(chip, chipnr);
>  
> @@ -4565,8 +4546,6 @@ static int nand_suspend(struct mtd_info *mtd)
>  	mutex_lock(&chip->lock);
>  	if (chip->ops.suspend)
>  		ret = chip->ops.suspend(chip);
> -	if (!ret)
> -		chip->suspended = 1;
>  	mutex_unlock(&chip->lock);
>  
>  	return ret;
> @@ -4580,15 +4559,10 @@ static void nand_resume(struct mtd_info *mtd)
>  {
>  	struct nand_chip *chip = mtd_to_nand(mtd);
>  
> +
>  	mutex_lock(&chip->lock);
> -	if (chip->suspended) {
> -		if (chip->ops.resume)
> -			chip->ops.resume(chip);
> -		chip->suspended = 0;
> -	} else {
> -		pr_err("%s called for a chip which is not in suspended state\n",
> -			__func__);
> -	}
> +	if (chip->ops.resume)
> +		chip->ops.resume(chip);
>  	mutex_unlock(&chip->lock);
>  }
>  
> diff --git a/include/linux/mtd/rawnand.h b/include/linux/mtd/rawnand.h
> index b2f9dd3cbd69..1198a6548912 100644
> --- a/include/linux/mtd/rawnand.h
> +++ b/include/linux/mtd/rawnand.h
> @@ -1237,9 +1237,7 @@ struct nand_secure_region {
>   * @pagecache.page: Page number currently in the cache. -1 means no page is
>   *                  currently cached
>   * @buf_align: Minimum buffer alignment required by a platform
> - * @lock: Lock protecting the suspended field. Also used to serialize accesses
> - *        to the NAND device
> - * @suspended: Set to 1 when the device is suspended, 0 when it's not
> + * @lock: Lock to serialize accesses to the NAND device
>   * @cur_cs: Currently selected target. -1 means no target selected, otherwise we
>   *          should always have cur_cs >= 0 && cur_cs < nanddev_ntargets().
>   *          NAND Controller drivers should not modify this value, but they're
> @@ -1293,7 +1291,6 @@ struct nand_chip {
>  
>  	/* Internals */
>  	struct mutex lock;
> -	unsigned int suspended : 1;
>  	int cur_cs;
>  	int read_retries;
>  	struct nand_secure_region *secure_regions;