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Date: Wed, 20 Dec 2023 17:21:22 +0100
From: Pali =?utf-8?B?Um9ow6Fy?= <pali@kernel.org>
To: Paul Menzel <pmenzel@molgen.mpg.de>
Cc: Jean Delvare <jdelvare@suse.com>, Andi Shyti <andi.shyti@kernel.org>,
	linux-i2c@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/2] i2c: i801: Add 0x29 as =?utf-8?B?ScKy?=
 =?utf-8?Q?C?= address for lis3lv02d in Dell Precision 3540
Message-ID: <20231220162122.y57rudx6qhxc6eku@pali>
References: <20231220161003.68310-1-pmenzel@molgen.mpg.de>
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User-Agent: NeoMutt/20180716

On Wednesday 20 December 2023 17:10:01 Paul Menzel wrote:
> On the Dell Precision 3540/0M14W7, BIOS 1.7.4 05/12/2020, Linux prints
> the warning below.
> 
>     i801_smbus 0000:00:1f.4: Accelerometer lis3lv02d is present on SMBus but its address is unknown, skipping registration
> 
> With the help of Wolfram Sang, the test to probe it on I²C bus 6 at address
> 0x29 was successful.
> 
>     $ cd /sys/bus/pci/drivers/i801_smbus/0000:00:1f.4
>     $ ls -d i2c-?
>     i2c-6
>     $ sudo i2cdetect 6
>     WARNING! This program can confuse your I2C bus, cause data loss and worse!
>     I will probe file /dev/i2c-6.
>     I will probe address range 0x08-0x77.
>     Continue? [Y/n] Y
>          0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
>     00:                         08 -- -- -- -- -- -- --
>     10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
>     20: -- -- -- -- -- -- -- -- -- 29 -- -- -- -- -- --
>     30: 30 -- -- -- -- 35 UU UU -- -- -- -- -- -- -- --
>     40: -- -- -- -- 44 -- -- -- -- -- -- -- -- -- -- --
>     50: UU -- 52 -- -- -- -- -- -- -- -- -- -- -- -- --
>     60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
>     70: -- -- -- -- -- -- -- --
> 
>     $ echo lis3lv02d 0x29 | sudo tee /sys/bus/i2c/devices/i2c-6/new_device
>     $ sudo dmesg
>     […]
>     [ 2110.787000] i2c i2c-6: new_device: Instantiated device lis3lv02d at 0x29
>     [ 2110.791932] lis3lv02d_i2c 6-0029: supply Vdd not found, using dummy regulator
>     [ 2110.791981] lis3lv02d_i2c 6-0029: supply Vdd_IO not found, using dummy regulator
>     [ 2110.809233] lis3lv02d: 8 bits 3DC sensor found
>     [ 2110.900668] input: ST LIS3LV02DL Accelerometer as /devices/platform/lis3lv02d/input/input23
> 
> So, the device has that accelerometer. Add the I2C address to the
> mapping list.
> 
> Link: https://lore.kernel.org/linux-i2c/97708c11-ac85-fb62-2c8e-d37739ca826f@molgen.mpg.de/
> Signed-off-by: Paul Menzel <pmenzel@molgen.mpg.de>

If the accelerometer is working fine then I have no objections.

Acked-by: Pali Rohár <pali@kernel.org>

Anyway, if you have a time then try to look into decompiled ACPI DSDT
table if Dell had not put somewhere this SMBus/I²C address of the
accelerometer. I remember that for older Latitude E6440 I looked into
every DSDT method related with accelerometer if there is not some
information but I have not find anything and also Dell confirmed that
this address information is not there present. I'm still hoping that
Dell put autodiscovery address for new machines somewhere...

And if you are more curious you can start investigation what are other
devices which i2cdetect showed (only those with UU are bound to some
kernel/userspace driver).

> ---
>  drivers/i2c/busses/i2c-i801.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/i2c/busses/i2c-i801.c b/drivers/i2c/busses/i2c-i801.c
> index 070999139c6d..cb9660f84117 100644
> --- a/drivers/i2c/busses/i2c-i801.c
> +++ b/drivers/i2c/busses/i2c-i801.c
> @@ -1230,6 +1230,7 @@ static const struct {
>  	 * Additional individual entries were added after verification.
>  	 */
>  	{ "Latitude 5480",      0x29 },
> +	{ "Precision 3540",     0x29 },
>  	{ "Vostro V131",        0x1d },
>  	{ "Vostro 5568",        0x29 },
>  };
> -- 
> 2.43.0
>