linux-kernel - Re: [PATCH v2 0/3] media: pci: intel: ivsc: Add driver of Intel Visual Sensing Controller(IVSC)

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Date:   Fri, 17 Mar 2023 10:58:34 +0200
From:   Sakari Ailus <sakari.ailus@...ux.intel.com>
To:     "Wu, Wentong" <wentong.wu@...el.com>
Cc:     Hans de Goede <hdegoede@...hat.com>,
        "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)

Hi Wentong,

On Fri, Mar 17, 2023 at 07:30:19AM +0000, Wu, Wentong wrote:
> 
> 
> > -----Original Message-----
> > From: Hans de Goede <hdegoede@...hat.com>
> > Sent: Thursday, March 16, 2023 5:04 PM
> > 
> > Hi,
> > 
> > On 3/16/23 03:58, Wu, Wentong wrote:
> > >
> > >
> > >> -----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
> > >
> > > Below is your dmesg log, the required SPI controller for IVSC isn't here.
> > >
> > > [   35.538114] ljca 2-6:1.0: acked sem wait timed out ret:0 timeout:20 ack:0
> > > [   35.538129] ljca 2-6:1.0: MNG_ENUM_SPI failed ret:-110 len:7 num:0
> > > [   35.538621] ljca 2-6:1.0: LJCA USB device init success
> > > [   35.538776] usbcore: registered new interface driver ljca
> > >
> > > Also I checked your SSDT, there is no IVSC device and the sensor
> > > device depends on
> > > INT3472 instead of IVSC device as on my setup.
> > 
> > Ack.
> > 
> > >> 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.
> > >
> > > Can we add IVSC device to acpi_honor_dep_ids, so that when everything
> > > is done during mei_ace probe, acpi_dev_clear_dependencies can make sensor
> > start probe?
> > 
> > Does the sensor ACPI device node have an ACPI _DEP on the IVSC device ?
> 
> Yes,
> 
> > 
> > If yes, then yes we can add the IVSC device to acpi_honor_dep_id and make
> > mei_ace probe call acpi_dev_clear_dependencies().
> 
> But I prefer the powerdown gpio model, because we have to follow the commands
> sequences as below which is required by firmware, runtime pm is hard to achieve this.

How so?

I don't insist on the runtime PM based solution but I'd rather not have
changes to virtually all sensor drivers --- this is an external chip to
them.

> +	/* switch camera sensor ownership to host */
> +	ret = ace_set_camera_owner(ACE_CAMERA_HOST);
> +	if (ret)
> +		goto error;
> +
> +	/* switch CSI-2 link to host */
> +	ret = csi_set_link_owner(CSI_LINK_HOST, callback, context);
> +	if (ret)
> +		goto release_camera;
> +
> +	/* configure CSI-2 link */
> +	ret = csi_set_link_cfg(nr_of_lanes, link_freq);
> +	if (ret)
> +		goto release_csi;

-- 
Kind regards,

Sakari Ailus