Hi, On 3/9/23 02:08, Wu, Wentong wrote: > > >> -----Original Message----- >> From: Hans de Goede <hdegoede@xxxxxxxxxx> >> 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@xxxxxxxxxxxxxxx> >>>> 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@xxxxxxxxxx> >>>>>> 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" ? > 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 >
