Re: Fwd: Surface Go VCM type (was: Need to pass acpi_enforce_resources=lax on the Surface Go (version1))

[Daniel Scally <djrscally@gmail.com>]

Hi Andy

On 01/11/2021 15:55, Andy Shevchenko wrote:
> On Fri, Oct 29, 2021 at 12:50:31PM +0100, Daniel Scally wrote:
>> Hi all
>>
>> +CC linux-media and libcamera-devel, as it's probably a good time to
>> broaden this out. Also Andy because I'm hoping you can help :) The
>> background of the discussion is about how we identify and enumerate
>> (correctly, I.E. with a type matching the vcm driver's i2c_device_id,
>> and there are a few different vcm's in scope which seem encoded in the
>> SSDB buffer) which VCM module is linked to a sensor in Intel's IPU3
>> centric ACPI tables. The I2C address for the device is just a second
>> I2cSerialBusV2 against the sensor's acpi device rather than a separate
>> one, which is no awkward. We also need to get firmware created for the
>> VCM such that the sensor will link to it via the lens-focus property.
>> On 28/10/2021 09:57, Hans de Goede wrote:
> ...
>
>> To throw a spanner in the works though; I noticed this delightful _CRS
>> for the OV9734 sensor of a  Surface Laptop 1 earlier:
>>
>> Method (_CRS, 0, Serialized)  // _CRS: Current Resource Settings
>> {
>>     Name (SBUF, ResourceTemplate ()
>>     {
>>         I2cSerialBusV2 (0x0036, ControllerInitiated, 0x00061A80,
>>             AddressingMode7Bit, "\\_SB.PCI0.I2C2",
>>             0x00, ResourceConsumer, , Exclusive,
>>             )
>>         I2cSerialBusV2 (0x0050, ControllerInitiated, 0x00061A80,
>>             AddressingMode7Bit, "\\_SB.PCI0.I2C2",
>>             0x00, ResourceConsumer, , Exclusive,
>>             )
>>         I2cSerialBusV2 (0x0051, ControllerInitiated, 0x00061A80,
>>             AddressingMode7Bit, "\\_SB.PCI0.I2C2",
>>             0x00, ResourceConsumer, , Exclusive,
>>             )
>>         I2cSerialBusV2 (0x0052, ControllerInitiated, 0x00061A80,
>>             AddressingMode7Bit, "\\_SB.PCI0.I2C2",
>>             0x00, ResourceConsumer, , Exclusive,
>>             )
>>         I2cSerialBusV2 (0x0053, ControllerInitiated, 0x00061A80,
>>             AddressingMode7Bit, "\\_SB.PCI0.I2C2",
>>             0x00, ResourceConsumer, , Exclusive,
>>             )
>>     })
>>     Return (SBUF) /* \_SB_.PCI0.I2C2.CAMF._CRS.SBUF */
>> }
>>
>> How do we know which one's the VCM when there's more than just two like
>> that? Andy: don't suppose you can shed any light there?
> Seems to me that the order is defined by address and if software engineers are
> not (so) crazy, it shouldn't deviate from device to device.
>
> At least this is stated in the internal documentation.
>
> The order is
>
> 1. Sensor (single addr)
> 2. VCM (single addr)
> 3. EEPROM (addr per page)


Thank you! That's really helpful, much appreciated.

> Interestingly that your list have no VCM in the _CRS defined...
>
> Not sure how to distinguish that if it's not a typo and indeed the case.
> Sounds like DMI quirk :-( again (something like 3-bit flag to define
> which devices are present in the _CRS taking into account the ordering
> requirements).


There's a field in the SSDB buffer against the sensor's acpi device,
with values from 0-4. We found an enumeration online, so we think that
the VCM in the surface go is a DW9719.