Message-ID: <DM6PR11MB43169899E53424334CA08E568DBC9@DM6PR11MB4316.namprd11.prod.outlook.com>
Date:   Thu, 16 Mar 2023 08:11:55 +0000
From:   "Wu, Wentong" <wentong.wu@...el.com>
To:     Hans de Goede <hdegoede@...hat.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)



> -----Original Message-----
> From: Hans de Goede <hdegoede@...hat.com>
> Sent: Thursday, March 9, 2023 11:24 PM
> 
> <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.

Thanks,

So the drivers of sensors connected to IVSC have to add power up/down code.

BR,
Wentong
> 
> 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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