[alsa-devel] How to handle jack detection through gpios

[Hans de Goede]

Hi,

On 03-11-17 13:41, Pierre-Louis Bossart wrote:
> On 11/3/17 3:41 AM, Hans de Goede wrote:
>> Hi All,
>>
>> Umberto Izzo (in the Cc) mailed me to see if I could help
>> with implementing headphone detection through GPIOS as I've
>> been doing all kinds of Bay / Cherry Trail related work
>> recently.
>>
>> Umberto found this commit:
>>
>> https://github.com/me176c-dev/kernel_asus_me176c/commit/498116d7e7b4718fa0655c4879e59a163b1dd85b
>>
>> Which looks interesting, but is specific to the RT5640
>> driver. Looking at my own test devices I found a device
>> with an ES8316 using a gpio for headphone detection.
>>
>> What Umberto and my device have in common is that
>> the GPIO to use is listed in the ACPI tables
>> under an AMCR0F28 device and that is also what the
>> above commit binds too.
> 
> This is not a generic solution, these sort of ACPI entries are only present in devices designed for Android, in Windows the STA_ method typically reports 0 (not present) - the ASL code is usually shared between Windows and Android devices but there are variables controlling what the run-time behavior is, mostly to avoid the yellow bang the windows device manager if there is a device without a driver.
> 
> Also you have two quirks for each of jack detection / button press, some platforms rely on codec-based detection and some of gpios directly connected to the SOC. We tried to port some of the code from Android a while ago but i haven't had time to maintain or even clean it. See
> https://github.com/plbossart/sound/pull/1

So one problem here is that your work is based on getting gpios
from the acpi_companion of the codec, but in the dsdt of Umberto's
device: https://github.com/sfumato77/DSDT/blob/master/dsdt.dsl
the gpio ("\\_SB.GPO2" pin 0x1b) is only part of the resources
list of the TIMC0F28 and the AMCR0F28 devices and on one
of my tablets with an es8316 which uses the same gpio for headphone
detection the same is true.

So as I said in my reply to Mark:

"It might be best to see if we can somehow search through the list
of ACPI devices from the codec driver and get to the GPIO
that way. I guess we will need a utility function for this to
share between codec drivers, since the same AMCR0F28 ACPI device
is used in DSTDs together with different codecs."

Would adding such a utility function to parse the gpio info
in the AMCR0F28 ACPI device on devices where this is necessary
be acceptable?

Of course using the AMCR0F28 ACPI device is not going to be
the right thing to do everywhere, so we are going to need a
(dmi-based) quirk table in the codec driver for this.

Regards,

Hans



> 
> 
>>
>> So I was wondering if there is a way to have a headphone
>> switch without tying it to a card, while userspace will
>> still know what to do ?
>>
>> ###
>>
>> Another (non audio) problem is that the AMCR0F28 ACPI
>> device seems to be present in the DSTD for almost all
>> Bay / Cherry Trail devices, but its _STA method always
>> returns 0 even on devices where we do need to use gpios
>> for headphone-detection.
>>
>> I'm thinking about solving this by adding the AMCR0F28
>> device to the list of always present ACPI devices, so that
>> the kernel ignores _STA and creates a platform device for
>> it. And then in the platform driver for the AMCR0F28
>> platform device use a DMI whitelist, this is not the
>> prettiest solution but it is the best I can come up with
>> atm. As said not really audio related,
>>
>> Regards,
>>
>> Hans
>>
>>
>