Re: [PATCH] HID: i2c: Call acpi_device_fix_up_power for ACPI-enumerated devices

[Hans de Goede <hdegoede@redhat.com>]

Hi,

On 09-05-17 09:12, Benjamin Tissoires wrote:
> Hi Hans,
> 
> On May 07 2017 or thereabouts, Hans de Goede wrote:
>> ACPI devices which do not have a _PSC method are assumed to have been
>> put in D0 by the BIOS, but for touchscreens that is not always true,
>> so call acpi_device_fix_up_power to explicitly put devices without a
>> _PSC method into D0 state.
>>
>> This fixes the SIS0817 i2c-hid touchscreen on a Peaq C1010 2-in-1
>> device failing to probe with a "hid_descr_cmd failed" error.
>>
>> Signed-off-by: Hans de Goede <hdegoede@redhat.com>
>> ---
>>   drivers/hid/i2c-hid/i2c-hid.c | 13 +++++++++++++
>>   1 file changed, 13 insertions(+)
>>
>> diff --git a/drivers/hid/i2c-hid/i2c-hid.c b/drivers/hid/i2c-hid/i2c-hid.c
>> index ea3c3546cef7..c716d9605940 100644
>> --- a/drivers/hid/i2c-hid/i2c-hid.c
>> +++ b/drivers/hid/i2c-hid/i2c-hid.c
>> @@ -960,6 +960,15 @@ static int i2c_hid_acpi_pdata(struct i2c_client *client,
>>   	return 0;
>>   }
>>   
>> +static void i2c_hid_acpi_fix_up_power(struct device *dev)
>> +{
>> +	acpi_handle handle = ACPI_HANDLE(dev);
>> +	struct acpi_device *adev;
>> +
>> +	if (handle && acpi_bus_get_device(handle, &adev) == 0)
>> +		acpi_device_fix_up_power(adev);
> 
> I am wondering if this is not something that should be handled by
> acpi-core or i2c-core. Looks like something pretty generic.

The acpi-core deliberately does not do this, as unconditionally
doing this for all devices is known to break things on some
platforms, see:

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=7cd8407
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=b9e95fc65eded

So calling this is something which needs to be done an a device-by-device
(usually actually on a driver-by-driver) basis.

I don't expect this to cause any problems for i2c-hid devices
(as the above commits shown once it was done for all ACPI enumerated devices)
and it is necessary for some i2c-hid devices.

> Also, isn't this also needed on resume (or reset_resume)?

After a suspend the device is in D3, so we will always execute _PS0
to put it back in D0. This is about devices without a _PSC method
(which allows querying the actual state) being in D3 on boot, rather
then the expected (and assumed) D0. Note that for devices with a _PSC
method calling acpi_device_fix_up_power() is a nop.

Regards,

Hans

>> +}
>> +
>>   static const struct acpi_device_id i2c_hid_acpi_match[] = {
>>   	{"ACPI0C50", 0 },
>>   	{"PNP0C50", 0 },
>> @@ -972,6 +981,8 @@ static inline int i2c_hid_acpi_pdata(struct i2c_client *client,
>>   {
>>   	return -ENODEV;
>>   }
>> +
>> +static inline void i2c_hid_acpi_fix_up_power(struct device *dev) {}
>>   #endif
>>   
>>   #ifdef CONFIG_OF
>> @@ -1070,6 +1081,8 @@ static int i2c_hid_probe(struct i2c_client *client,
>>   	if (ret < 0)
>>   		goto err;
>>   
>> +	i2c_hid_acpi_fix_up_power(&client->dev);
>> +
>>   	pm_runtime_get_noresume(&client->dev);
>>   	pm_runtime_set_active(&client->dev);
>>   	pm_runtime_enable(&client->dev);
>> -- 
>> 2.12.2
>>