Re: [PATCH] dell-smm-hwmon.c: Add XPS 9570 to supported devices list

Pali Rohár
2018-12-05T09:15:28Z

Hi!

On Thursday 29 November 2018 21:42:54 Michele Sorcinelli wrote:
> I've been playing with smm.c from a old version of i8kutils, that
> is just an userspace utility to trigger the SMM RPC:
>
> http://sprunge.us/llxG7R
>
> I used that in combination with the following test script:
>
> http://sprunge.us/izJmQK
>
> I managed to run that on a XPS 9560 and 9570 and compare the results.
>
> XPS 9560: http://sprunge.us/xCLNSy
> XPS 9570: http://sprunge.us/wSFTKs
>
> The main difference between 9560 and 9570 is that the calls to get
> the type of either fan or temperature sensor are not working (they all
> return 0xfff in the eax register), where in the 9560 they're returning
> proper values.

So it looks like that SMM on you machine does not support call to get
type of temperature sensor. And dell-smm-hwmon.c uses type of sensor to
detect if sensor is present or not.

Also from that output it looks like that you have 8 temperature sensors
present, but dell-smm-hwmon.c currently supports only first 4.

If you want to have support for temperature sensors on your machine, you
can look at code in i8k_init_hwmon() how fans are initialized. Code
there first check if fan status does not produce error OR fan type does
not produce error. And you can use same logic for temperature sensors.

And if you want to support all 8 temp sensors, you need to extend
dell-smm-hwmon.c code to support more then 4 temp sensors.

This means that you would not see temperature sensors names as your SMM
does not provide them. But it is a problem at all?

> However, it looks like the call for reading values (fan speed or
> temperatures) are all returning proper values in 9570 as well.
>
> I'm assuming the following:
>
> - API should be the same between 9560 and 9670 (why should Dell change
> it just now, and just for a single feature?);

I think API was not changed. Just one RPC over SMM function is not
supported.

> - in the 9670 the type calls are not implemented correctly;
> - the sensor indexes should be correct (because they work when used to
> read the temperature directly)
>
> I also tried using higher indexes but I always get 0xffff.
>
> We could either wait for Dell to eventually release a firmware update
> that implements those calls correctly or we could force the reading of
> the temperatures even if the type is not returned properly (although
> I didn't know how to map the sensor with the proper label).

Have you reported bug to Dell? If not, then Dell probably do not know
about it and so cannot fix anything.

> I'm not keen to try other unknown procedures as I don't know what could
> happen, but I've found that other documented procedures are working properly
> (eg. set fan speed, read firmware version, disable fan control,
> enable fan control, etc.), so again I think the API shouldn't have changed.
>
> Let me know your thoughts.
>
> Thanks,
> Michele.
>
> On 11/29/18 9:48 AM, Pali Rohár wrote:
> > On Wednesday 28 November 2018 23:23:07 Michele Sorcinelli wrote:
> > > I tried to debug the temperature sensor probing with some printk()
> > > around the code... it looks like the ssm calls are all returning -22
> > > as result:
> > >
> > > [ 90.565793] Calling i8k_get_temp_type(0)
> > > [ 90.565795] Inside i8k_get_temp_type() with sensors = 0
> > > [ 90.565795] Performing i8k_smm call
> > > [ 90.567708] Result of the i8k_smm call: -22
> > > [ 90.567708] Return value of i8k_get_temp_type: -22
> > > [ 90.567709] Result of i8k_get_temp_type(0): -22
> > > [ 90.567709] Calling i8k_get_temp_type(1)
> > > [ 90.567710] Inside i8k_get_temp_type() with sensors = 1
> > > [ 90.567710] Performing i8k_smm call
> > > [ 90.568567] Result of the i8k_smm call: -22
> > > [ 90.568567] Return value of i8k_get_temp_type: -22
> > > [ 90.568568] Result of i8k_get_temp_type(0): -22
> > > [ 90.568568] Calling i8k_get_temp_type(2)
> > > [ 90.568568] Inside i8k_get_temp_type() with sensors = 2
> > > [ 90.568569] Performing i8k_smm call
> > > [ 90.569441] Result of the i8k_smm call: -22
> > > [ 90.569441] Return value of i8k_get_temp_type: -22
> > > [ 90.569442] Result of i8k_get_temp_type(0): -22
> > > [ 90.569442] Calling i8k_get_temp_type(3)
> > > [ 90.569442] Inside i8k_get_temp_type() with sensors = 3
> > > [ 90.569443] Performing i8k_smm call
> > > [ 90.570321] Result of the i8k_smm call: -22
> > > [ 90.570322] Return value of i8k_get_temp_type: -22
> > > [ 90.570322] Result of i8k_get_temp_type(0): -22
> > >
> > > So this must be the reason for which sensors aren't detected.
> >
> > Yes. SMM just say "I do not support this temp sensor". Also it is
> > possible that Dell's SMM does not implement it at all.
> >
> > You can try to play with it more and check if temp sensor does not have
> > higher index.
> >
> > But I cannot help more. As you said it is RPC black-box.
> >
> > > AFAIK, SSM code is much of a black-box and finding how to fix
> > > this will probably require some reverse engineering.
> > >
> > > However, apart from this and the fact that kernel hangs during
> > > the SSM call (that is reasonable and again not much can't be done),
> > > everything looks fine.
> > >
> > > Let me know if you want me to include more information in the commit message
> > > for the patch or want me to do more testing.
> >
> > That is enough. You can add my
> >
> > Reviewed-by: Pali Rohár <pali.rohar@gmail.com>
> >
> > and hwmon maintainers could pick up this patch.
> >
> > > On 11/28/18 1:01 PM, Michele Sorcinelli wrote:
> > > > Yes, values are reported correctly when the fan are on. I tested it
> > > > by disabling the firmware automatic control using
> > > > https://github.com/TomFreudenberg/dell-bios-fan-control and then running
> > > > i8kfan 1 1 and i8kfan 2 2, which brought the fans to 2500 and 5100
> > > > respectively.
> > > >
> > > > When automatic control is on I can see intermediate speeds as well.
> > > >
> > > > Is there anything that can be done to help the driver to discover
> > > > the temperature sensors?
> > > >
> > > > On 11/28/18 12:56 PM, Pali Rohár wrote:
> > > > > On Wednesday 28 November 2018 12:30:31 Michele Sorcinelli wrote:
> > > > > > The output of sensors related to the is:
> > > > > >
> > > > > > dell_smm-virtual-0
> > > > > > Adapter: Virtual device
> > > > > > fan1:           0 RPM
> > > > > > fan2:           0 RPM
> > > > >
> > > > > Ok, this means that both fans are turned off.
> > > > >
> > > > > When you start fans, have both number meaningful/correct value?
> > > > >
> > > > > > This suggests that temperature sensors are not discovered.
> > > > >
> > > > > Yes, probably they are unsupported or not discovered. But this is not
> > > > > a problem.
> > > > >
> > > > > > Speeds reported in the hwmon interface are consistent with the others.
> > > > > >
> > > > > >
> > > > > > On 11/27/18 11:06 PM, Michele Sorcinelli wrote:
> > > > > > > Allow the module to be loaded on Dell XPS 9570, without having to use
> > > > > > > the "force=1" option. The module loads without problems, and reports
> > > > > > > correct fan values:
> > > > > > >
> > > > > > >       $ time cat /proc/i8k
> > > > > > >       1.0 1.5 -1 35 0 0 0 0 -1 -22
> > > > > > >       cat /proc/i8k  0.00s user 0.00s system 7% cpu 0.033 total
> > > > > > >
> > > > > > > However, the call may freeze the kernel for a very small time due to
> > > > > > > code running in the SSM layer. This is a known issue with
> > > > > > > the driver, and
> > > > > > > can be reproduced with other supported models. Average execution
> > > > > > > time is 33 ms.
> > > > > > >
> > > > > > > The command line tools from i8kutils can properly set the fan speed,
> > > > > > > although the firmware will override it, unless automatic fan
> > > > > > > control is disabled with the proper SSM call.
> > > > > > >
> > > > > > > Average fans speed (when firwmare automatic control is off):
> > > > > > >
> > > > > > > STATE -> RPM
> > > > > > > 0 0 -> 0 0
> > > > > > > 1 1 -> 2500 2500
> > > > > > > 2 2 -> 5100 5100
> > > > > > > 3 3 -> same as 2 2
> > > > > > > ---
> > > > > > >    drivers/hwmon/dell-smm-hwmon.c | 7 +++++++
> > > > > > >    1 file changed, 7 insertions(+)
> > > > > > >
> > > > > > > diff --git a/drivers/hwmon/dell-smm-hwmon.c
> > > > > > > b/drivers/hwmon/dell-smm-hwmon.c
> > > > > > > index 9d3ef879d..367a8a617 100644
> > > > > > > --- a/drivers/hwmon/dell-smm-hwmon.c
> > > > > > > +++ b/drivers/hwmon/dell-smm-hwmon.c
> > > > > > > @@ -1017,6 +1017,13 @@ static const struct dmi_system_id
> > > > > > > i8k_dmi_table[] __initconst = {
> > > > > > >                DMI_MATCH(DMI_PRODUCT_NAME, "XPS 15 9560"),
> > > > > > >            },
> > > > > > >        },
> > > > > > > +    {
> > > > > > > +        .ident = "Dell XPS 15 9570",
> > > > > > > +        .matches = {
> > > > > > > +            DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
> > > > > > > +            DMI_MATCH(DMI_PRODUCT_NAME, "XPS 15 9570"),
> > > > > > > +        },
> > > > > > > +    },
> > > > > > >        { }
> > > > > > >    };
> > > > > > >
> > > > >
> >

--
Pali Rohár
pali.rohar@gmail.com