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

[Michele Sorcinelli <michelesr@autistici.org>]

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.

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.

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"),
>>>> +        },
>>>> +    },
>>>>        { }
>>>>    };
>>>>
>>