From: "Brigham Campbell" <me@brighamcampbell.com>
To: "Stephen Horvath" <s.horvath@outlook.com.au>,
"Brigham Campbell" <me@brighamcampbell.com>,
"Wolfram Sang" <wsa+renesas@sang-engineering.com>,
<linux-i2c@vger.kernel.org>
Cc: "Jean Delvare" <jdelvare@suse.com>,
"Benoît Monin" <benoit.monin@bootlin.com>
Subject: Re: [PATCH i2c-tools] TODO: add file and describe items for the 4.5 release
Date: Mon, 06 Jul 2026 00:33:43 -0600 [thread overview]
Message-ID: <DJRA1PB8LKKJ.2RTZWEP2LVRFF@brighamcampbell.com> (raw)
In-Reply-To: <SYBPR01MB4586AD69D431CAD2D26ADD68C5F12@SYBPR01MB4586.ausprd01.prod.outlook.com>
On Sun Jul 5, 2026 at 11:19 PM MDT, Stephen Horvath wrote:
> If you've got the spd5118 kernel module loaded (which usually happens
> automatically), you just have to run `sudo ./decode-dimms`. You can
> manually bind spd5118 if it isn't autodetecting, your dimms should be on
> your i801 bus (or PIIX4 for AMD), usually with an address between 0x50
> to 0x57.
No, the spd5118 module doesn't appear to be loaded automatically:
```
$ lsmod | grep spd5118
$ zgrep SENSORS_SPD5118 /proc/config.gz
CONFIG_SENSORS_SPD5118=m
CONFIG_SENSORS_SPD5118_DETECT=y
```
Using `i2cdetect` on the i801 SMBus controller, I see that it reports no
attached i2c devices:
```
$ sudo ./tools/i2cdetect -y /dev/i2c-15
0 1 2 3 4 5 6 7 8 9 a b c d e f
00: -- -- -- -- -- -- -- --
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
70: -- -- -- -- -- -- -- --
$
```
Interestingly, I see warnings in dmesg upon running the above i2cdetect
command. Taking a quick look at the kernel code, this appears to be
caused by some transient controller hardware busy state which is
overcome by the kernel's bus arbitration retry logic (See
`drivers/i2c/busses/i2c-i801.c:1552`). It's strange that a bus with no
devices attached would ever become busy...
```
...
[ +0.000009] i801_smbus 0000:00:1f.4: SMBus is busy, can't use it!
[ +0.000010] i801_smbus 0000:00:1f.4: SMBus is busy, can't use it!
[ +0.000010] i801_smbus 0000:00:1f.4: SMBus is busy, can't use it!
[ +0.000009] i801_smbus 0000:00:1f.4: SMBus is busy, can't use it!
[ +0.000010] i801_smbus 0000:00:1f.4: SMBus is busy, can't use it!
...
```
In any case, if I am unable to exercise your code, I would still be glad
to review it.
Cheers,
Brigham
next prev parent reply other threads:[~2026-07-06 6:31 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-07-05 18:10 [PATCH i2c-tools] TODO: add file and describe items for the 4.5 release Wolfram Sang
2026-07-06 4:45 ` Brigham Campbell
2026-07-06 5:19 ` Stephen Horvath
2026-07-06 6:33 ` Brigham Campbell [this message]
2026-07-06 8:04 ` Benoît Monin
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