Message-ID: <bb608934-23a6-213b-ab28-5dd66afd88e5@redhat.com>
Date:   Thu, 9 Mar 2023 16:24:00 +0100
From:   Hans de Goede <hdegoede@...hat.com>
To:     "Wu, Wentong" <wentong.wu@...el.com>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>
Cc:     "mchehab@...nel.org" <mchehab@...nel.org>,
        "linux-media@...r.kernel.org" <linux-media@...r.kernel.org>,
        "Pandruvada, Srinivas" <srinivas.pandruvada@...el.com>,
        "pierre-louis.bossart@...ux.intel.com" 
        <pierre-louis.bossart@...ux.intel.com>,
        "Wang, Zhifeng" <zhifeng.wang@...el.com>,
        "Ye, Xiang" <xiang.ye@...el.com>,
        "Qiu, Tian Shu" <tian.shu.qiu@...el.com>,
        "Cao, Bingbu" <bingbu.cao@...el.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 0/3] media: pci: intel: ivsc: Add driver of Intel
 Visual Sensing Controller(IVSC)

<re-added the previous Cc list, which I dropped because of the large attachments>

Hi Wentong,

On 3/9/23 15:29, Wu, Wentong wrote:
> Hi Hans,
> 
> Thanks
> 
> And AFAICT, there is no IVSC device on your Dell Latitude 9420 where the platform is based on TGL instead of ADL, and I have never heard IVSC runs on TGL,  if no IVSC, INT3472 will control sensor's power.
> And I will double confirm with people who know dell product well tomorrow.

Ah, I was under the impression that there was an IVSC there because:

1. The sensor driver for the used sensor (tries to) poke the IVSC
2. Things did not work without building the IVSC drivers, but that might
   be due to a dependency on the LCJA GPIO expander instead

But you might very well be right, that would also explain the
"intel vsc not ready" messages in dmesg.

If with the IVSC case the IVSC controls the power to the sensor too,
then another option might be to model the I2C-switch + the power-control
as a powerdown GPIO for the sensor, which most sensor drivers already
try to use. The advantage of doing this would be that GPIO lookups
can reference the GPIO provider + consumer by device-name so then
we don't need to have both devices instantiated at the time of
adding the GPIO lookup.   And in that case we could e.g. add the lookup
before registering the I2C controller.

Sakari, what do you think of instead of using runtime-pm + devlinks
having the IVSC code export a powerdown GPIO to the sensor ?

This also decouples the ivsc powerstate from the sensor power-state
which might be useful if we ever want to use some of the more
advanced ivsc features, where AFAICT the ivsc fully controls the sensor.

Regards,

Hans




>> -----Original Message-----
>> From: Hans de Goede <hdegoede@...hat.com>
>> Sent: Thursday, March 9, 2023 9:30 PM
>> To: Wu, Wentong <wentong.wu@...el.com>
>> Subject: Re: [PATCH v2 0/3] media: pci: intel: ivsc: Add driver of Intel Visual
>> Sensing Controller(IVSC)
>>
>> Hi Wentong,
>>
>> Attached are the requested dmesg + acpidump for the Dell Latitude 9420.
>>
>> Regards,
>>
>> Hans
>>
>>
>>
>>
>> On 3/9/23 14:21, Wu, Wentong wrote:
>>> Hi
>>>
>>>> -----Original Message-----
>>>> From: Hans de Goede <hdegoede@...hat.com>
>>>> Sent: Thursday, March 9, 2023 5:28 PM
>>>>
>>>> Hi,
>>>>
>>>> On 3/9/23 02:08, Wu, Wentong wrote:
>>>>>
>>>>>
>>>>>> -----Original Message-----
>>>>>> From: Hans de Goede <hdegoede@...hat.com>
>>>>>> Sent: Tuesday, March 7, 2023 5:10 PM
>>>>>>
>>>>>> Hi,
>>>>>>
>>>>>> On 3/7/23 09:40, Wu, Wentong wrote:
>>>>>>>
>>>>>>>
>>>>>>>> -----Original Message-----
>>>>>>>> From: Sakari Ailus <sakari.ailus@...ux.intel.com>
>>>>>>>> Sent: Tuesday, March 7, 2023 4:30 PM
>>>>>>>>
>>>>>>>> Hi Wentong,
>>>>>>>>
>>>>>>>> On Tue, Mar 07, 2023 at 08:17:04AM +0000, Wu, Wentong wrote:
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>> -----Original Message-----
>>>>>>>>>> From: Hans de Goede <hdegoede@...hat.com>
>>>>>>>>>> Sent: Wednesday, March 1, 2023 6:42 PM
>>>>>>>>>>
>>>>>>>>>> Hi,
>>>>>>>>>>
>>>>>>>>>> On 3/1/23 11:34, Sakari Ailus wrote:
>>>>>>>>>>> Hi Wentong,
>>>>>>>>>>>
>>>>>>>>>>> On Mon, Feb 13, 2023 at 10:23:44AM +0800, Wentong Wu wrote:
>>>>>>>>>>>> Intel Visual Sensing Controller (IVSC), codenamed "Clover
>>>>>>>>>>>> Falls", is a companion chip designed to provide secure and
>>>>>>>>>>>> low power vision capability to IA platforms. IVSC is
>>>>>>>>>>>> available in existing commercial platforms from multiple OEMs.
>>>>>>>>>>>>
>>>>>>>>>>>> The primary use case of IVSC is to bring in context awareness.
>>>>>>>>>>>> IVSC interfaces directly with the platform main camera sensor
>>>>>>>>>>>> via a CSI-2 link and processes the image data with the
>>>>>>>>>>>> embedded AI engine. The detected events are sent over I2C to
>>>>>>>>>>>> ISH (Intel Sensor Hub) for additional data fusion from multiple
>> sensors.
>>>>>>>>>>>> The fusion results are used to implement advanced use cases like:
>>>>>>>>>>>>  - Face detection to unlock screen
>>>>>>>>>>>>  - Detect user presence to manage backlight setting or waking
>>>>>>>>>>>> up system
>>>>>>>>>>>>
>>>>>>>>>>>> Since the Image Processing Unit(IPU) used on the host
>>>>>>>>>>>> processor needs to configure the CSI-2 link in normal camera
>>>>>>>>>>>> usages, the
>>>>>>>>>>>> CSI-2 link and camera sensor can only be used in
>>>>>>>>>>>> mutually-exclusive ways by host IPU and IVSC. By default the
>>>>>>>>>>>> IVSC owns the CSI-2 link and camera sensor. The IPU driver
>>>>>>>>>>>> can take ownership of the CSI-2 link and camera sensor using
>>>>>>>>>>>> interfaces provided
>>>>>>>> by this IVSC driver.
>>>>>>>>>>>>
>>>>>>>>>>>> Switching ownership requires an interface with two different
>>>>>>>>>>>> hardware modules inside IVSC. The software interface to these
>>>>>>>>>>>> modules is via Intel MEI (The Intel Management Engine) commands.
>>>>>>>>>>>> These two hardware modules have two different MEI UUIDs to
>>>>>>>>>>>> enumerate. These hardware
>>>>>>>>>> modules are:
>>>>>>>>>>>>  - ACE (Algorithm Context Engine): This module is for
>>>>>>>>>>>> algorithm computing when IVSC owns camera sensor. Also ACE
>>>>>>>>>>>> module controls camera sensor's ownership. This hardware
>>>>>>>>>>>> module is used to set ownership
>>>>>>>>>> of camera sensor.
>>>>>>>>>>>>  - CSI (Camera Serial Interface): This module is used to
>>>>>>>>>>>> route camera sensor data either to IVSC or to host for IPU
>>>>>>>>>>>> driver and
>>>>>>>> application.
>>>>>>>>>>>>
>>>>>>>>>>>> IVSC also provides a privacy mode. When privacy mode is
>>>>>>>>>>>> turned on, camera sensor can't be used. This means that both
>>>>>>>>>>>> ACE and host IPU can't get image data. And when this mode is
>>>>>>>>>>>> turned on, host IPU driver is informed via a registered
>>>>>>>>>>>> callback, so that user can be
>>>>>>>> notified.
>>>>>>>>>>>>
>>>>>>>>>>>> In summary, to acquire ownership of camera by IPU driver,
>>>>>>>>>>>> first ACE module needs to be informed of ownership and then
>>>>>>>>>>>> to setup MIPI CSI-2 link for the camera sensor and IPU.
>>>>>>>>>>>
>>>>>>>>>>> I thought this for a while and did some research, and I can
>>>>>>>>>>> suggest the
>>>>>>>>>>> following:
>>>>>>>>>>>
>>>>>>>>>>> - The IVSC sub-device implements a control for privacy
>>>>>> (V4L2_CID_PRIVACY
>>>>>>>>>>>   is a good fit).
>>>>>>>>>>>
>>>>>>>>>>> - Camera sensor access needs to be requested from IVSC before
>>>>>>>>>>> accessing
>>>>>>>> the
>>>>>>>>>>>   sensor via I²C. The IVSC ownership control needs to be in the right
>>>>>>>>>>>   setting for this to work, and device links can be used for that
>> purpose
>>>>>>>>>>>   (see device_link_add()). With DL_FLAG_PM_RUNTIME and
>>>>>>>>>> DL_FLAG_RPM_ACTIVE,
>>>>>>>>>>>   the supplier devices will be PM runtime resumed before the
>> consumer
>>>>>>>>>>>   (camera sensor). As these devices are purely virtual on host
>>>>>>>>>>> side and
>>>> has
>>>>>>>>>>>   no power state as such, you can use runtime PM callbacks to
>>>>>>>>>>> transfer
>>>>>> the
>>>>>>>>>>>   ownership.
>>>>>>>>>>
>>>>>>>>>> Interesting proposal to use device-links + runtime-pm for this
>>>>>>>>>> instead of modelling this as an i2c-mux. FWIW I'm fine with
>>>>>>>>>> going this route instead of using an i2c-mux approach.
>>>>>>>>>>
>>>>>>>>>> I have been thinking about the i2c-mux approach a bit and the
>>>>>>>>>> problem is that we are not really muxing but want to turn
>>>>>>>>>> on/off control and AFAIK the i2c-mux framework simply leaves
>>>>>>>>>> the mux muxed to the last used i2c-chain, so control will never
>>>>>>>>>> be released when the i2c
>>>>>>>> transfers are done.
>>>>>>>>>>
>>>>>>>>>> And if were to somehow modify things (or maybe there already is
>>>>>>>>>> some release
>>>>>>>>>> callback) then the downside becomes that the i2c-mux core code
>>>>>>>>>> operates at the i2c transfer level. So each i2c read/write
>>>>>>>>>> would then enable +
>>>>>>>> disavle control.
>>>>>>>>>>
>>>>>>>>>> Modelling this using something like runtime pm as such is a
>>>>>>>>>> much better fit because then we request control once on probe /
>>>>>>>>>> stream-on and release it once we are fully done, rather then
>>>>>>>>>> requesting + releasing control once per i2c- transfer.
>>>>>>>>>
>>>>>>>>> Seems runtime pm can't fix the problem of initial i2c transfer
>>>>>>>>> during sensor driver probe, probably we have to switch to
>>>>>>>>> i2c-mux modeling
>>>>>> way.
>>>>>>>>
>>>>>>>> What do you mean? The supplier devices are resumed before the
>>>>>>>> driver's probe is called.
>>>>>>>
>>>>>>> But we setup the link with device_link_add during IVSC driver's
>>>>>>> probe, we can't guarantee driver probe's sequence.
>>>>>>
>>>>>> Then maybe we need to do the device_link_add somewhere else.
>>>>>
>>>>> sensor's parent is the LJCA I2C device whose driver is being
>>>>> upstream https://www.spinics.net/lists/kernel/msg4702552.htmland and
>>>>> sensor's power is controlled by IVSC instead of INT3472 if IVSC enabled.
>>>>
>>>> I believe that the INT3472 code is still involved at least on a Dell
>>>> Latitude 9420 the INT3472 code still needs to set the clock-enable
>>>> and the privacy-LED GPIOs otherwise the main camera won't work.
>>>>
>>>> So I'm not sure what you mean with "sensor's power is controlled by
>>>> IVSC instead of INT3472" ?
>>>
>>> Could you please share your kernel log and DSDT? Thanks
>>>
>>> BR,
>>> Wentong
>>>>
>>>>
>>>>> struct device_link *device_link_add(struct device *consumer,
>>>>>                                     struct device *supplier, u32
>>>>> flags)
>>>>>
>>>>> So probably we have to add above device_link_add in LJCA I2C's
>>>>> driver, and we can find the consumer(camera sensor) with ACPI API,
>>>>> but the supplier, mei_ace, is mei client device under mei framework
>>>>> and it's dynamically allocated device instead of ACPI device,
>>>>> probably I can find its parent with some ACPI lookup from this LJCA
>>>>> I2C device, but unfortunately mei framework doesn't export the API
>>>>> to find mei client device with its parent bus device(struct mei_device).
>>>>>
>>>>> I'm not sure if modeling this mei_ace as LJCA I2C's runtime power
>>>>> control is acceptable, if yes, probably this mei_ace driver have to
>>>>> go with LJCA I2C device driver.
>>>>
>>>> Looking at the ACPI table the sensor ACPI device has 2 _DEP-s listed
>>>> the I2C controller and the INT3472 device. Since we are already doing
>>>> similar setup in the INT3472 device that seems like a good place to
>>>> add the device_link()-s (it can return -EPROBE_DEFER to wait for the mei_ace
>> to show up).
>>>>
>>>> But when the INT3472 code runs, the consumer device does not exist
>>>> yet and AFAICT the same is true when the LCJA i2c-controller driver is getting
>> registered.
>>>> The consumer only exists when the i2c_client is instantiated and at
>>>> that point the sensor drivers probe() method can run immediately and
>>>> we are too late to add the device_link.
>>>>
>>>> As a hobby project I have been working on atomisp2 support and I have
>>>> a similar issue there. There is no INT3472 device there, but there is
>>>> a _DSM method which needs to be used to figure out which ACPI GPIO
>>>> resource is reset / powerdown and if the GPIOs are active-low or active high.
>>>>
>>>> I have written a little helper function to call the _DSM and to then
>>>> turn this into lookups and call devm_acpi_dev_add_driver_gpios().
>>>>
>>>> Since on atomisp2 we cannot use the INT3472 driver to delay the
>>>> sensor-driver probe and have the INT3472 driver setup the GPIO
>>>> lookup, at least for the sensor drivers used with
>>>> atomisp2 there is going to be a need to add a single line to probe() like this:
>>>>
>>>> 	v4l2_get_acpi_sensor_info(&i2c_client->dev, NULL);
>>>>
>>>> To me it sounds like we need to do something similar here and extend
>>>> the helper function which I have written (but not yet submitted upstream) :
>>>>
>>>> https://github.com/jwrdegoede/linux-
>>>> sunxi/commit/e2287979db43d46fa7d354c1bde92eb6219b613d
>>>>
>>>> To also setup the device-links needed for the runtime-pm solution to
>>>> getting the i2c passed through to the sensor.
>>>>
>>>> Ideally v4l2_get_acpi_sensor_info() should return void (easier to use
>>>> in the sensor drivers) but I think it should return an int, so that
>>>> it can e.g. return - EPROBE_DEFER to wait for the mei_ace.
>>>>
>>>> Regards,
>>>>
>>>> Hans
>>>>
>>>>
>>>>
>>>>
>>>>>> The mainline kernel delays probing of camera sensors on Intel
>>>>>> platforms until the INT3472 driver has probed the INT3472 device on
>>>>>> which the sensors have an ACPI _DEP.
>>>>>>
>>>>>> This is already used to make sure that clock lookups and regulator
>>>>>> info is in place before the sensor's probe() function runs.
>>>>>>
>>>>>> So that when the driver does clk_get() it succeeds and so that
>>>>>> regulator_get() does not end up returning a dummy regulator.
>>>>>>
>>>>>> So I think the code adding the device_link-s for the IVSC should be
>>>>>> added
>>>>>> to: drivers/platform/x86/intel/int3472/discrete.c and then the
>>>>>> runtime-resume will happen before the sensor's probe() function runs.
>>>>>>
>>>>>> Likewise drivers/platform/x86/intel/int3472/discrete.c should also
>>>>>> ensure that the ivsc driver's probe() has run before it calls
>>>> acpi_dev_clear_dependencies().
>>>>>>
>>>>>> The acpi_dev_clear_dependencies() call in discrete.c tells the ACPI
>>>>>> subsystem to go ahead and create the i2c-clients for the sensors
>>>>>> and allow the sensor drivers to get loaded and probe the sensor.
>>>>>>
>>>>>> Regards,
>>>>>>
>>>>>> Hans
>>>>>
>>>

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