Re: [PATCH 13/18] ipu3-cio2: Add functionality allowing software_node connections to sensors on platforms designed for Windows

[Dan Scally <djrscally@gmail.com>]

On 02/12/2020 10:38, Sakari Ailus wrote:
> Hi Laurent,
>
> On Wed, Dec 02, 2020 at 12:30:53AM +0200, Laurent Pinchart wrote:
>> Hi Daniel,
>>
>> On Tue, Dec 01, 2020 at 10:08:25PM +0000, Dan Scally wrote:
>>> On 30/11/2020 17:09, Laurent Pinchart wrote:
>>>> On Mon, Nov 30, 2020 at 01:31:24PM +0000, Daniel Scally wrote:
>>>>> Currently on platforms designed for Windows, connections between CIO2 and
>>>>> sensors are not properly defined in DSDT. This patch extends the ipu3-cio2
>>>>> driver to compensate by building software_node connections, parsing the
>>>>> connection properties from the sensor's SSDB buffer.
>>>>>
>>>>> Suggested-by: Jordan Hand <jorhand@linux.microsoft.com>
>>>>> Signed-off-by: Daniel Scally <djrscally@gmail.com>
>>>>> ---
>>>>> Changes since RFC v3:
>>>>>
>>>>> 	- Removed almost all global variables, dynamically allocated
>>>>> 	the cio2_bridge structure, plus a bunch of associated changes
>>>>> 	like 
>>>>> 	- Added a new function to ipu3-cio2-main.c to check for an 
>>>>> 	existing fwnode_graph before calling cio2_bridge_init()
>>>>> 	- Prefixed cio2_bridge_ to any variables and functions that
>>>>> 	lacked it
>>>>> 	- Assigned the new fwnode directly to the sensor's ACPI device
>>>>> 	fwnode as secondary. This removes the requirement to delay until
>>>>> 	the I2C devices are instantiated before ipu3-cio2 can probe, but
>>>>> 	it has a side effect, which is that those devices then grab a ref
>>>>> 	to the new software_node. This effectively prevents us from
>>>>> 	unloading the driver, because we can't free the memory that they
>>>>> 	live in whilst the device holds a reference to them. The work
>>>>> 	around at the moment is to _not_ unregister the software_nodes
>>>>> 	when ipu3-cio2 is unloaded; this becomes a one-time 'patch', that
>>>>> 	is simply skipped if the module is reloaded.
>>>>> 	- Moved the sensor's SSDB struct to be a member of cio2_sensor
>>>>> 	- Replaced ints with unsigned ints where appropriate
>>>>> 	- Iterated over all ACPI devices of a matching _HID rather than
>>>>> 	just the first to ensure we handle a device with multiple sensors
>>>>> 	of the same model.
>>>>>
>>>>>  MAINTAINERS                                   |   1 +
>>>>>  drivers/media/pci/intel/ipu3/Kconfig          |  18 ++
>>>>>  drivers/media/pci/intel/ipu3/Makefile         |   1 +
>>>>>  drivers/media/pci/intel/ipu3/cio2-bridge.c    | 260 ++++++++++++++++++
>>>>>  drivers/media/pci/intel/ipu3/cio2-bridge.h    | 108 ++++++++
>>>>>  drivers/media/pci/intel/ipu3/ipu3-cio2-main.c |  27 ++
>>>>>  drivers/media/pci/intel/ipu3/ipu3-cio2.h      |   6 +
>>>>>  7 files changed, 421 insertions(+)
>>>>>  create mode 100644 drivers/media/pci/intel/ipu3/cio2-bridge.c
>>>>>  create mode 100644 drivers/media/pci/intel/ipu3/cio2-bridge.h
>>>>>
>>>>> diff --git a/MAINTAINERS b/MAINTAINERS
>>>>> index 9702b886d6a4..188559a0a610 100644
>>>>> --- a/MAINTAINERS
>>>>> +++ b/MAINTAINERS
>>>>> @@ -8927,6 +8927,7 @@ INTEL IPU3 CSI-2 CIO2 DRIVER
>>>>>  M:	Yong Zhi <yong.zhi@intel.com>
>>>>>  M:	Sakari Ailus <sakari.ailus@linux.intel.com>
>>>>>  M:	Bingbu Cao <bingbu.cao@intel.com>
>>>>> +M:	Dan Scally <djrscally@gmail.com>
>>>>>  R:	Tianshu Qiu <tian.shu.qiu@intel.com>
>>>>>  L:	linux-media@vger.kernel.org
>>>>>  S:	Maintained
>>>>> diff --git a/drivers/media/pci/intel/ipu3/Kconfig b/drivers/media/pci/intel/ipu3/Kconfig
>>>>> index 82d7f17e6a02..2b3350d042be 100644
>>>>> --- a/drivers/media/pci/intel/ipu3/Kconfig
>>>>> +++ b/drivers/media/pci/intel/ipu3/Kconfig
>>>>> @@ -16,3 +16,21 @@ config VIDEO_IPU3_CIO2
>>>>>  	  Say Y or M here if you have a Skylake/Kaby Lake SoC with MIPI CSI-2
>>>>>  	  connected camera.
>>>>>  	  The module will be called ipu3-cio2.
>>>>> +
>>>>> +config CIO2_BRIDGE
>>>>> +	bool "IPU3 CIO2 Sensors Bridge"
>>>>> +	depends on VIDEO_IPU3_CIO2
>>>>> +	help
>>>>> +	  This extension provides an API for the ipu3-cio2 driver to create
>>>>> +	  connections to cameras that are hidden in SSDB buffer in ACPI. It
>>>>> +	  can be used to enable support for cameras in detachable / hybrid
>>>>> +	  devices that ship with Windows.
>>>>> +
>>>>> +	  Say Y here if your device is a detachable / hybrid laptop that comes
>>>>> +	  with Windows installed by the OEM, for example:
>>>>> +
>>>>> +	  	- Microsoft Surface models (except Surface Pro 3)
>>>>> +		- The Lenovo Miix line (for example the 510, 520, 710 and 720)
>>>>> +		- Dell 7285
>>>>> +
>>>>> +	  If in doubt, say N here.
>>>>> diff --git a/drivers/media/pci/intel/ipu3/Makefile b/drivers/media/pci/intel/ipu3/Makefile
>>>>> index 429d516452e4..933777e6ea8a 100644
>>>>> --- a/drivers/media/pci/intel/ipu3/Makefile
>>>>> +++ b/drivers/media/pci/intel/ipu3/Makefile
>>>>> @@ -2,3 +2,4 @@
>>>>>  obj-$(CONFIG_VIDEO_IPU3_CIO2) += ipu3-cio2.o
>>>>>  
>>>>>  ipu3-cio2-y += ipu3-cio2-main.o
>>>>> +ipu3-cio2-$(CONFIG_CIO2_BRIDGE) += cio2-bridge.o
>>>>> diff --git a/drivers/media/pci/intel/ipu3/cio2-bridge.c b/drivers/media/pci/intel/ipu3/cio2-bridge.c
>>>>> new file mode 100644
>>>>> index 000000000000..fd3f8ba07274
>>>>> --- /dev/null
>>>>> +++ b/drivers/media/pci/intel/ipu3/cio2-bridge.c
>>>>> @@ -0,0 +1,260 @@
>>>>> +// SPDX-License-Identifier: GPL-2.0
>>>>> +/* Author: Dan Scally <djrscally@gmail.com> */
>>>> Could you please add a blank line here ?
>>> Yes
>>>
>>>>> +#include <linux/acpi.h>
>>>>> +#include <linux/device.h>
>>>>> +#include <linux/i2c.h>
>>>> Is this header needed ?
>>>>
>>>>> +#include <linux/kernel.h>
>>>>> +#include <linux/module.h>
>>>> And this one ?
>>>>
>>>>> +#include <linux/pci.h>
>>>>> +#include <linux/property.h>
>>>>> +#include <media/v4l2-subdev.h>
>>>> And this one ?
>>> Ah yes - bit sloppy, they're orphaned from earlier versions, sorry about
>>> that.
>>>
>>>>> +
>>>>> +#include "cio2-bridge.h"
>>>>> +
>>>>> +/*
>>>>> + * Extend this array with ACPI Hardware ID's of devices known to be working.
>>>>> + * Do not add a HID for a sensor that is not actually supported.
>>>>> + */
>>>>> +static const char * const cio2_supported_devices[] = {
>>>> Maybe cio2_supported_sensors ?
>>> Sure
>>>
>>>>> +	"INT33BE",
>>>>> +	"OVTI2680",
>>>>> +};
>>>>> +
>>>>> +static int cio2_bridge_read_acpi_buffer(struct acpi_device *adev, char *id,
>>>>> +					void *data, u32 size)
>>>>> +{
>>>>> +	struct acpi_buffer buffer = { ACPI_ALLOCATE_BUFFER, NULL };
>>>>> +	union acpi_object *obj;
>>>>> +	acpi_status status;
>>>>> +	int ret;
>>>>> +
>>>>> +	status = acpi_evaluate_object(adev->handle, id, NULL, &buffer);
>>>>> +	if (ACPI_FAILURE(status))
>>>>> +		return -ENODEV;
>>>>> +
>>>>> +	obj = buffer.pointer;
>>>>> +	if (!obj) {
>>>>> +		dev_err(&adev->dev, "Couldn't locate ACPI buffer\n");
>>>>> +		return -ENODEV;
>>>>> +	}
>>>>> +
>>>>> +	if (obj->type != ACPI_TYPE_BUFFER) {
>>>>> +		dev_err(&adev->dev, "Not an ACPI buffer\n");
>>>>> +		ret = -ENODEV;
>>>>> +		goto out_free_buff;
>>>>> +	}
>>>>> +
>>>>> +	if (obj->buffer.length > size) {
>>>>> +		dev_err(&adev->dev, "Given buffer is too small\n");
>>>>> +		ret = -EINVAL;
>>>>> +		goto out_free_buff;
>>>>> +	}
>>>>> +
>>>>> +	memcpy(data, obj->buffer.pointer, obj->buffer.length);
>>>>> +	ret = obj->buffer.length;
>>>>> +
>>>>> +out_free_buff:
>>>>> +	kfree(buffer.pointer);
>>>>> +	return ret;
>>>>> +}
>>>>> +
>>>>> +static void cio2_bridge_init_property_names(struct cio2_sensor *sensor)
>>>>> +{
>>>>> +	strcpy(sensor->prop_names.clock_frequency, "clock-frequency");
>>>>> +	strcpy(sensor->prop_names.rotation, "rotation");
>>>>> +	strcpy(sensor->prop_names.bus_type, "bus-type");
>>>>> +	strcpy(sensor->prop_names.data_lanes, "data-lanes");
>>>>> +	strcpy(sensor->prop_names.remote_endpoint, "remote-endpoint");
>>>> This is a bit fragile, as there's no len check. How about the following
>>>> ?
>>>> static const struct cio2_property_names prop_names = {
>>>> 	.clock_frequency = "clock-frequency",
>>>> 	.rotation = "rotation",
>>>> 	.bus_type = "bus-type",
>>>> 	.data_lanes = "data-lanes",
>>>> 	.remote_endpoint = "remote-endpoint",
>>>> };
>>>>
>>>> static void cio2_bridge_init_property_names(struct cio2_sensor *sensor)
>>>> {
>>>> 	sensor->prop_names = prop_names;
>>>> }
>>>>
>>>> This shoudl generate a compilation warning if the string is too long.
>>>>
>>>> You could even inline that line in
>>>> cio2_bridge_create_fwnode_properties().
>>> Yes, I like that, thanks - I'll make the change.
>>>
>>>>> +}
>>>>> +
>>>>> +static void cio2_bridge_create_fwnode_properties(struct cio2_sensor *sensor)
>>>>> +{
>>>>> +	unsigned int i;
>>>>> +
>>>>> +	cio2_bridge_init_property_names(sensor);
>>>>> +
>>>>> +	for (i = 0; i < 4; i++)
>>>>> +		sensor->data_lanes[i] = i + 1;
>>>> Is there no provision in the SSDB for data lane remapping ?
>>> Sorry; don't follow what you mean by data lane remapping here.
>> Some CSI-2 receivers can remap data lanes. The routing inside the SoC
>> from the data lane input pins to the PHYs is configurable. This makes
>> board design easier as you can route the data lanes to any of the
>> inputs. That's why the data lanes DT property is a list of lane numbers
>> instead of a number of lanes. I'm actually not sure if the CIO2 supports
>> this.
> To my knowledge it does not. Only the number of lanes allocated to
> different ports matters.
>
So nothing to change here then I think?
>>>>> @@ -0,0 +1,108 @@
>>>>> +/* SPDX-License-Identifier: GPL-2.0 */
>>>>> +/* Author: Dan Scally <djrscally@gmail.com> */
>>>>> +#ifndef __CIO2_BRIDGE_H
>>>>> +#define __CIO2_BRIDGE_H
>>>>> +
>>>>> +#include <linux/property.h>
>>>>> +
>>>>> +#define CIO2_HID				"INT343E"
>>>>> +#define CIO2_NUM_PORTS			  4
>>>> There are a few rogue spaces before '4'.
>>> Argh, thanks, this is the curse of using VS code on multiple machines...
>> I recommend vim ;-)
> What is VS code? Very Serious Code?

Visual Studio Code - it has some nice features, but the
facepalm-to-productivity ratio is a bit high.

> I can recommend Emacs; that could help, too.