[PATCH 0/2] media: m2m-deinterlace: add device-tree support

[PATCH 0/2] media: m2m-deinterlace: add device-tree support

[Matthew Majewski]

Hello all, this patch series adds device-tree support for the generic
m2m-deinterlace driver.

A specific dma controller channel can now be provided to the driver
via the dt, but the driver still supports the original dma query if an
of_node is not present. This should preserve backwards compatibility
with platform drivers that directly instantiate the device.

Probing the m2m-deinterlace device via device-tree was tested on the
BeagleBone Black with an m2m-appropriate edma channel.

Best,

Matthew Majewski

Matthew Majewski (2):
  media: dt-bindings: Add dt bindings for m2m-deinterlace device
  media: m2m-deinterlace: add device-tree support

 .../bindings/media/m2m-deinterlace.yaml       | 41 +++++++++++++++++++
 drivers/media/platform/m2m-deinterlace.c      | 25 ++++++++---
 2 files changed, 60 insertions(+), 6 deletions(-)
 create mode 100644 Documentation/devicetree/bindings/media/m2m-deinterlace.yaml

-- 
2.25.1

[PATCH 1/2] media: dt-bindings: Add dt bindings for m2m-deinterlace device

[Matthew Majewski]

Create a new yaml schema file to describe the device tree bindings for
the generic m2m-deinterlace driver.

Signed-off-by: Matthew Majewski <mattwmajewski@gmail.com>
---
 .../bindings/media/m2m-deinterlace.yaml       | 41 +++++++++++++++++++
 1 file changed, 41 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/media/m2m-deinterlace.yaml

diff --git a/Documentation/devicetree/bindings/media/m2m-deinterlace.yaml b/Documentation/devicetree/bindings/media/m2m-deinterlace.yaml
new file mode 100644
index 000000000000..3ac9c1e7be88
--- /dev/null
+++ b/Documentation/devicetree/bindings/media/m2m-deinterlace.yaml
@@ -0,0 +1,41 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/media/m2m-deinterlace.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: M2M Deinterlacer
+
+maintainers:
+ - Mauro Carvalho Chehab <mchehab@kernel.org>
+
+description: |
+  A generic memory2memory device for deinterlacing video
+  using dmaengine.
+
+properties:
+  compatible:
+    const: m2m-deinterlace
+
+  dma-names:
+    items:
+      - const: rxtx
+
+  dmas:
+    items:
+      - description: mem-to-mem capable DMA channel
+
+required:
+  - compatible
+  - dma-names
+  - dmas
+
+additionalProperties: false
+
+examples:
+  - |
+    m2m-deinterlace {
+        compatible = "m2m-deinterlace";
+        dma-names = "rxtx";
+        dmas = <&edma 20 0>;
+    };
-- 
2.25.1

Re: [PATCH 1/2] media: dt-bindings: Add dt bindings for m2m-deinterlace device

[Krzysztof Kozlowski]

On 12/02/2025 18:09, Matthew Majewski wrote:
> Create a new yaml schema file to describe the device tree bindings for
> the generic m2m-deinterlace driver.


Bindings are for hardware, not drivers, and usually not generic.

Please describe here exemplary devices.

> 
> Signed-off-by: Matthew Majewski <mattwmajewski@gmail.com>
> ---
>  .../bindings/media/m2m-deinterlace.yaml       | 41 +++++++++++++++++++
>  1 file changed, 41 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/media/m2m-deinterlace.yaml
> 
> diff --git a/Documentation/devicetree/bindings/media/m2m-deinterlace.yaml b/Documentation/devicetree/bindings/media/m2m-deinterlace.yaml
> new file mode 100644
> index 000000000000..3ac9c1e7be88
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/media/m2m-deinterlace.yaml
> @@ -0,0 +1,41 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/media/m2m-deinterlace.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: M2M Deinterlacer
> +
> +maintainers:
> + - Mauro Carvalho Chehab <mchehab@kernel.org>
> +
> +description: |
> +  A generic memory2memory device for deinterlacing video
> +  using dmaengine.

And what is this generic device supposed to do? What fits to generic device?

> +
> +properties:
> +  compatible:
> +    const: m2m-deinterlace
> +
> +  dma-names:
> +    items:
> +      - const: rxtx
> +
> +  dmas:
> +    items:
> +      - description: mem-to-mem capable DMA channel
> +
> +required:
> +  - compatible
> +  - dma-names
> +  - dmas
> +
> +additionalProperties: false
> +
> +examples:
> +  - |
> +    m2m-deinterlace {
> +        compatible = "m2m-deinterlace";
> +        dma-names = "rxtx";
> +        dmas = <&edma 20 0>;


This all looks rather like bindings for driver and not even quite
generic because looks quite simple. I guess media folks will provide
more input, but anyway it looks a bit not-DT-enough.

> +    };


Best regards,
Krzysztof

Re: [PATCH 1/2] media: dt-bindings: Add dt bindings for m2m-deinterlace device

[Matthew Majewski]

Hi Krzysztof, thanks for the quick feedback. 

On Wed, 2025-02-12 at 18:22 +0100, Krzysztof Kozlowski wrote:
> On 12/02/2025 18:09, Matthew Majewski wrote:
> > Create a new yaml schema file to describe the device tree bindings
> > for
> > the generic m2m-deinterlace driver.
> 
> 
> Bindings are for hardware, not drivers, and usually not generic.
> 

Ok, I'll change the wording from "driver" to "device" in V2.

> Please describe here exemplary devices.

The m2m-deinterlace device can be used on any hardware that provides a
MEM_TO_MEM and interleaved capable dma channel. I'll note that in the
commit message for V2 as well.

> > 
> > +description: |
> > +  A generic memory2memory device for deinterlacing video
> > +  using dmaengine.
> 
> And what is this generic device supposed to do? What fits to generic
> device?
> 

The term "generic" was taken from the driver description. It's generic
insofar as it only relies on the dmaengine API for processing (and
hence is relatively platform agnostic).

I will add more information about the device in the description for V2.
I'll also mention that it's intended for converting between interlaced
and non-interlaced formats by line-doubling. 

> > +
> > +properties:
> > +  compatible:
> > +    const: m2m-deinterlace
> > +
> > +  dma-names:
> > +    items:
> > +      - const: rxtx
> > +
> > +  dmas:
> > +    items:
> > +      - description: mem-to-mem capable DMA channel
> > +
> > +required:
> > +  - compatible
> > +  - dma-names
> > +  - dmas
> > +
> > +additionalProperties: false
> > +
> > +examples:
> > +  - |
> > +    m2m-deinterlace {
> > +        compatible = "m2m-deinterlace";
> > +        dma-names = "rxtx";
> > +        dmas = <&edma 20 0>;
> 
> 
> This all looks rather like bindings for driver and not even quite
> generic because looks quite simple. I guess media folks will provide
> more input, but anyway it looks a bit not-DT-enough.
> 
> > +    };

Yes, the bindings are much simpler than a typical media device, but
that is because the m2m-deinterlace device only needs to be provided a
handle to a dma channel to function properly. My reasoning for adding 
dt-bindings for this device is because it is a consumer of a dma-
channel and the dt bindings are a platform-agnostic way to be able to
provide a specific dma channel to the device.

As an example, say on an embedded device I have a dma controller which
provides multiple interleaved MEM_TO_MEM capable channels. I want the
m2m-deinterlace device to consume one particular channel because it is
higher-priority than the others. With these dt-bindings I can simply
specify the correct dma channel that should be used. Without the
device-tree bindings I would have to manually edit the driver to filter
for the correct dma channel to be used, but then the device is no
longer "generic".

It would be helpful to hear what the media people have to say about it.
The m2m-deinterlace device is a bit of an edge-case since it's not
quite a "virtual" device since it relies on the presence of specific
dma hardware. However, it doesn't follow the typical conventions of any
other in-tree media driver that consumes a dma channel, which all seem
to have dt-bindings. 

Best,
Matthew

Re: [PATCH 1/2] media: dt-bindings: Add dt bindings for m2m-deinterlace device

[Krzysztof Kozlowski]

On 12/02/2025 23:29, Matthew Majewski wrote:
> Hi Krzysztof, thanks for the quick feedback. 
> 
> On Wed, 2025-02-12 at 18:22 +0100, Krzysztof Kozlowski wrote:
>> On 12/02/2025 18:09, Matthew Majewski wrote:
>>> Create a new yaml schema file to describe the device tree bindings
>>> for
>>> the generic m2m-deinterlace driver.
>>
>>
>> Bindings are for hardware, not drivers, and usually not generic.
>>
> 
> Ok, I'll change the wording from "driver" to "device" in V2.
> 
>> Please describe here exemplary devices.
> 
> The m2m-deinterlace device can be used on any hardware that provides a
> MEM_TO_MEM and interleaved capable dma channel. I'll note that in the
> commit message for V2 as well.

I asked to give names of actual hardware you are writing bindings for.

> 
>>>
>>> +description: |
>>> +  A generic memory2memory device for deinterlacing video
>>> +  using dmaengine.
>>
>> And what is this generic device supposed to do? What fits to generic
>> device?
>>
> 
> The term "generic" was taken from the driver description. It's generic
> insofar as it only relies on the dmaengine API for processing (and
> hence is relatively platform agnostic).
> 
> I will add more information about the device in the description for V2.
> I'll also mention that it's intended for converting between interlaced
> and non-interlaced formats by line-doubling. 
> 
>>> +
>>> +properties:
>>> +  compatible:
>>> +    const: m2m-deinterlace
>>> +
>>> +  dma-names:
>>> +    items:
>>> +      - const: rxtx
>>> +
>>> +  dmas:
>>> +    items:
>>> +      - description: mem-to-mem capable DMA channel
>>> +
>>> +required:
>>> +  - compatible
>>> +  - dma-names
>>> +  - dmas
>>> +
>>> +additionalProperties: false
>>> +
>>> +examples:
>>> +  - |
>>> +    m2m-deinterlace {
>>> +        compatible = "m2m-deinterlace";
>>> +        dma-names = "rxtx";
>>> +        dmas = <&edma 20 0>;
>>
>>
>> This all looks rather like bindings for driver and not even quite
>> generic because looks quite simple. I guess media folks will provide
>> more input, but anyway it looks a bit not-DT-enough.
>>
>>> +    };
> 
> Yes, the bindings are much simpler than a typical media device, but
> that is because the m2m-deinterlace device only needs to be provided a
> handle to a dma channel to function properly. My reasoning for adding 

Really only this? How do you reset the device? How do you clock it (or
does it come with internal oscillator?) How do you program anything
there if there are no resources?


> dt-bindings for this device is because it is a consumer of a dma-
> channel and the dt bindings are a platform-agnostic way to be able to
> provide a specific dma channel to the device.
> 
> As an example, say on an embedded device I have a dma controller which
> provides multiple interleaved MEM_TO_MEM capable channels. I want the

I asked about the names already, still nothing.

> m2m-deinterlace device to consume one particular channel because it is
> higher-priority than the others. With these dt-bindings I can simply
> specify the correct dma channel that should be used. Without the
> device-tree bindings I would have to manually edit the driver to filter
> for the correct dma channel to be used, but then the device is no
> longer "generic".
> 
> It would be helpful to hear what the media people have to say about it.

Then wait before sending new version.



Best regards,
Krzysztof

Re: [PATCH 1/2] media: dt-bindings: Add dt bindings for m2m-deinterlace device

[Rob Herring (Arm)]

On Wed, 12 Feb 2025 12:09:00 -0500, Matthew Majewski wrote:
> Create a new yaml schema file to describe the device tree bindings for
> the generic m2m-deinterlace driver.
> 
> Signed-off-by: Matthew Majewski <mattwmajewski@gmail.com>
> ---
>  .../bindings/media/m2m-deinterlace.yaml       | 41 +++++++++++++++++++
>  1 file changed, 41 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/media/m2m-deinterlace.yaml
> 

My bot found errors running 'make dt_binding_check' on your patch:

yamllint warnings/errors:
./Documentation/devicetree/bindings/media/m2m-deinterlace.yaml:10:2: [warning] wrong indentation: expected 2 but found 1 (indentation)

dtschema/dtc warnings/errors:

doc reference errors (make refcheckdocs):

See https://patchwork.ozlabs.org/project/devicetree-bindings/patch/20250212170901.3881838-2-mattwmajewski@gmail.com

The base for the series is generally the latest rc1. A different dependency
should be noted in *this* patch.

If you already ran 'make dt_binding_check' and didn't see the above
error(s), then make sure 'yamllint' is installed and dt-schema is up to
date:

pip3 install dtschema --upgrade

Please check and re-submit after running the above command yourself. Note
that DT_SCHEMA_FILES can be set to your schema file to speed up checking
your schema. However, it must be unset to test all examples with your schema.

Re: [PATCH 1/2] media: dt-bindings: Add dt bindings for m2m-deinterlace device

[Matthew Majewski]

Hi Rob, thanks for the feedback. 

On Wed, 2025-02-12 at 13:26 -0600, Rob Herring (Arm) wrote:
> 
> If you already ran 'make dt_binding_check' and didn't see the above
> error(s), then make sure 'yamllint' is installed and dt-schema is up
> to
> date:
> 

Yup, I missed a yaml syntax error and didn't notice because I was
missing yamllint and dt_binding_check came back ok. Will fix for V2...
thanks again. 

Best,
Matthew

[PATCH 2/2] media: m2m-deinterlace: add device-tree support

[Matthew Majewski]

Add support for loading the m2m-deinterlace driver through the
device-tree.

Prefer to query the dma device through dma_request_chan(), which will
get the dma device information from the device-tree node if
present. Otherwise, fall back to the original dma_request_channel() to
preserve backwards compatibility.

Signed-off-by: Matthew Majewski <mattwmajewski@gmail.com>
---
 drivers/media/platform/m2m-deinterlace.c | 25 ++++++++++++++++++------
 1 file changed, 19 insertions(+), 6 deletions(-)

diff --git a/drivers/media/platform/m2m-deinterlace.c b/drivers/media/platform/m2m-deinterlace.c
index 5188f3189096..ba4e4ee6ad34 100644
--- a/drivers/media/platform/m2m-deinterlace.c
+++ b/drivers/media/platform/m2m-deinterlace.c
@@ -11,6 +11,7 @@
 #include <linux/interrupt.h>
 #include <linux/dmaengine.h>
 #include <linux/platform_device.h>
+#include <linux/module.h>
 
 #include <media/v4l2-mem2mem.h>
 #include <media/v4l2-device.h>
@@ -914,7 +915,6 @@ static int deinterlace_probe(struct platform_device *pdev)
 {
 	struct deinterlace_dev *pcdev;
 	struct video_device *vfd;
-	dma_cap_mask_t mask;
 	int ret = 0;
 
 	pcdev = devm_kzalloc(&pdev->dev, sizeof(*pcdev), GFP_KERNEL);
@@ -923,9 +923,16 @@ static int deinterlace_probe(struct platform_device *pdev)
 
 	spin_lock_init(&pcdev->irqlock);
 
-	dma_cap_zero(mask);
-	dma_cap_set(DMA_INTERLEAVE, mask);
-	pcdev->dma_chan = dma_request_channel(mask, NULL, pcdev);
+	if (pdev->dev.of_node) {
+		pcdev->dma_chan = dma_request_chan(&pdev->dev, "rxtx");
+	} else {
+		dma_cap_mask_t mask;
+
+		dma_cap_zero(mask);
+		dma_cap_set(DMA_INTERLEAVE, mask);
+		pcdev->dma_chan = dma_request_channel(mask, NULL, pcdev);
+	}
+
 	if (!pcdev->dma_chan)
 		return -ENODEV;
 
@@ -989,12 +996,18 @@ static void deinterlace_remove(struct platform_device *pdev)
 	dma_release_channel(pcdev->dma_chan);
 }
 
+static const struct of_device_id deinterlace_dt_match[] = {
+	{ .compatible = "m2m-deinterlace" },
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, deinterlace_dt_match);
+
 static struct platform_driver deinterlace_pdrv = {
 	.probe		= deinterlace_probe,
 	.remove		= deinterlace_remove,
 	.driver		= {
-		.name	= MEM2MEM_NAME,
+		.name		= MEM2MEM_NAME,
+		.of_match_table = deinterlace_dt_match,
 	},
 };
 module_platform_driver(deinterlace_pdrv);
-
-- 
2.25.1