linux-kernel - Re: [PATCH] mtd: spi-nor: stop printing superfluous debug info

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Date:   Tue, 28 Nov 2023 10:10:54 +0100
From:   Michael Walle <michael@...le.cc>
To:     Miquel Raynal <miquel.raynal@...tlin.com>
Cc:     Tudor Ambarus <tudor.ambarus@...aro.org>, jaimeliao.tw@...il.com,
        jaimeliao@...c.com.tw, pratyush@...nel.org, richard@....at,
        linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mtd: spi-nor: stop printing superfluous debug info

Hi,

>> > The mtd data can be obtain with the mtd ioctls and the SPI NOR
>> > flash name can be determined interrogating the sysfs entries.
>> > Stop polluting the kernel log.
>> >
>> > Signed-off-by: Tudor Ambarus <tudor.ambarus@...aro.org>
>> >
>> > ---
>> >  drivers/mtd/spi-nor/core.c | 19 -------------------
>> >  1 file changed, 19 deletions(-)
>> >
>> > diff --git a/drivers/mtd/spi-nor/core.c b/drivers/mtd/spi-nor/core.c
>> > index 25a64c65717d..6de76fd009d1 100644
>> > --- a/drivers/mtd/spi-nor/core.c
>> > +++ b/drivers/mtd/spi-nor/core.c
>> > @@ -3517,25 +3517,6 @@ int spi_nor_scan(struct spi_nor *nor, const char > *name,
>> >  	/* No mtd_info fields should be used up to this point. */
>> >  	spi_nor_set_mtd_info(nor);
>> >
>> > -	dev_info(dev, "%s (%lld Kbytes)\n", info->name,
>> > -			(long long)mtd->size >> 10);
>> 
>> I'd lower this to dev_dbg() and print the jedec id. It might come in
>> handy for a quick glance during bootup if debug is enabled.
> 
> Ack. Although, your boot time will almost be unaffected if you don't
> print the info messages to the console. What takes the most time is not
> writing to the kernel buffer, it's to display the lines on a serial
> console, and dev_info() are by default discarded, you need to select a
> lower log level manually, and if you do that it means you're not
> looking for quick boot times but rather more for additional 
> information.

Also with recent (or planned, dunno the current state) printk won't wait
anymore for the slowest console. I really don't have a strong opinion,
either dev_info(jedec_id) or dev_dbg(jedec_id). Whatever Tudor prefers.

>> > -	dev_dbg(dev,
>> > -		"mtd .name = %s, .size = 0x%llx (%lldMiB), "
>> > -		".erasesize = 0x%.8x (%uKiB) .numeraseregions = %d\n",
>> > -		mtd->name, (long long)mtd->size, (long long)(mtd->size >> 20),
>> > -		mtd->erasesize, mtd->erasesize / 1024, mtd->numeraseregions);
>> > -
>> > -	if (mtd->numeraseregions)
>> > -		for (i = 0; i < mtd->numeraseregions; i++)
>> > -			dev_dbg(dev,
>> > -				"mtd.eraseregions[%d] = { .offset = 0x%llx, "
>> > -				".erasesize = 0x%.8x (%uKiB), "
>> > -				".numblocks = %d }\n",
>> > -				i, (long long)mtd->eraseregions[i].offset,
>> > -				mtd->eraseregions[i].erasesize,
>> > -				mtd->eraseregions[i].erasesize / 1024,
>> > -				mtd->eraseregions[i].numblocks);
>> >  	return 0;
>> 
>> Part of this is already available through the spi-nor debugfs, 
>> although not
>> the actual mtd properties. These I think, should go into the mtdcore
>> itself if really needed. Either through dev_dbg() or debugfs.
> 
> Maybe we don't need this at all, as long as one message remains about
> the JEDEC ID, but keep in mind that spi-nors are commonly storing the
> rootfs and if your spi-nor does not boot you don't have a userspace yet
> and all the debugfs entries are purely useless.

Good point.

Just curious, do you know any boards which has the rootfs writable on
the spi-nor flash?

-michael