linux-kernel - Re: [PATCH v2 1/1] mtd: ubi: skip programming unused bits in ubi headers

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Message-ID: <37a8a673-4c5e-fd61-ae63-6059be311a34@huawei.com>
Date: Fri, 14 Nov 2025 17:28:41 +0800
From: Zhihao Cheng <chengzhihao1@...wei.com>
To: Cheng Ming Lin <linchengming884@...il.com>, <richard@....at>,
	<miquel.raynal@...tlin.com>, <vigneshr@...com>,
	<linux-mtd@...ts.infradead.org>, <linux-kernel@...r.kernel.org>
CC: <alvinzhou@...c.com.tw>, <leoyu@...c.com.tw>, Cheng Ming Lin
	<chengminglin@...c.com.tw>
Subject: Re: [PATCH v2 1/1] mtd: ubi: skip programming unused bits in ubi
 headers

在 2025/11/14 10:44, Cheng Ming Lin 写道:
> From: Cheng Ming Lin <chengminglin@...c.com.tw>
> 
> This patch prevents unnecessary programming of bits in ec_hdr and
> vid_hdr that are not used or read during normal UBI operation. These
> unused bits are typcially already set to 1 in erased flash and do not
> need to be explicitly programmed to 0 if they are not used.
> 
> Programming such unused areas offers no functional benefit and may
> result in unnecessary flash wear, reducing the overall lifetime of the
> device. By skipping these writes, we preserve the flash state as much as
> possible and minimize wear caused by redundant operations.
> 
> This change ensures that only necessary fields are written when preparing
> UBI headers, improving flash efficiency without affecting functionality.
> 
> Additionally, the Kioxia TC58NVG1S3HTA00 datasheet (page 63) also notes
> that continuous program/erase cycling with a high percentage of '0' bits
> in the data pattern can accelerate block endurance degradation.
> This further supports avoiding large 0x00 patterns.
> 
> Link: https://europe.kioxia.com/content/dam/kioxia/newidr/productinfo/datasheet/201910/DST_TC58NVG1S3HTA00-TDE_EN_31442.pdf
> 
> Signed-off-by: Cheng Ming Lin <chengminglin@...c.com.tw>
> ---
>   drivers/mtd/ubi/io.c | 10 ++++++++++
>   1 file changed, 10 insertions(+)

Reviewed-by: Zhihao Cheng <chengzhihao1@...wei.com>
> 
> diff --git a/drivers/mtd/ubi/io.c b/drivers/mtd/ubi/io.c
> index a4999bce4..dfb9c27c0 100644
> --- a/drivers/mtd/ubi/io.c
> +++ b/drivers/mtd/ubi/io.c
> @@ -868,6 +868,8 @@ int ubi_io_write_ec_hdr(struct ubi_device *ubi, int pnum,
>   		return -EROFS;
>   	}
>   
> +	memset((char *)ec_hdr + UBI_EC_HDR_SIZE, 0xFF, ubi->ec_hdr_alsize - UBI_EC_HDR_SIZE);
> +
>   	err = ubi_io_write(ubi, ec_hdr, pnum, 0, ubi->ec_hdr_alsize);
>   	return err;
>   }
> @@ -1150,6 +1152,14 @@ int ubi_io_write_vid_hdr(struct ubi_device *ubi, int pnum,
>   		return -EROFS;
>   	}
>   
> +	if (ubi->vid_hdr_shift) {
> +		memset((char *)p, 0xFF, ubi->vid_hdr_shift);
> +		memset((char *)p + ubi->vid_hdr_shift + UBI_VID_HDR_SIZE, 0xFF,
> +		       ubi->vid_hdr_alsize - (ubi->vid_hdr_shift + UBI_VID_HDR_SIZE));
> +	} else {
> +		memset((char *)p + UBI_VID_HDR_SIZE, 0xFF, ubi->vid_hdr_alsize - UBI_VID_HDR_SIZE);
> +	}
> +
>   	err = ubi_io_write(ubi, p, pnum, ubi->vid_hdr_aloffset,
>   			   ubi->vid_hdr_alsize);
>   	return err;
>