[Query] : DT: Adding mezzanine board

[Query] : DT: Adding mezzanine board

[Lad, Prabhakar]

Hi,

I am working Renesas RZ/Gx platforms, these boards have support for
connecting MIPI adapter mezzanine board [1]. To enable this support I
am planning to create a dtsi which will include the board file and
enable the necessary VIN/CSI and the camera endpoint.

For example: to add support for G2E board I would create a file named
r8a774c0-cat874-mipi-adapter.dtsi which will include the board file
r8a774c0.dtsi and enable necessary VIN/CSI/Camera endpoint and when
user wants to enable this support for the G2E board he could just
include r8a774c0-cat874-mipi-adapter.dtsi to r8a774c0-cat874.dts

Would this be a good approach or is there an alternative way which I am missing.

[1] https://github.com/Kevin-WSCU/96Boards-Camera/blob/master/AISTARVISION%20MIPI%20Adapter%20V2.1/AISTARVISION%20MIPI%20Adapter%20V2.1.pdf

Cheers,
--Prabhakar Lad

Re: [Query] : DT: Adding mezzanine board

[Laurent Pinchart]

Hi Prabhakar,

On Wed, Feb 19, 2020 at 11:42:42AM +0000, Lad, Prabhakar wrote:
> Hi,
> 
> I am working Renesas RZ/Gx platforms, these boards have support for
> connecting MIPI adapter mezzanine board [1]. To enable this support I
> am planning to create a dtsi which will include the board file and
> enable the necessary VIN/CSI and the camera endpoint.
> 
> For example: to add support for G2E board I would create a file named
> r8a774c0-cat874-mipi-adapter.dtsi which will include the board file
> r8a774c0.dtsi and enable necessary VIN/CSI/Camera endpoint and when
> user wants to enable this support for the G2E board he could just
> include r8a774c0-cat874-mipi-adapter.dtsi to r8a774c0-cat874.dts
> 
> Would this be a good approach or is there an alternative way which I am missing.

DT overlays are another option. They can't be applied on a running
system though. It doesn't seem like the mezzanine boards can be detected
by the boot loader, so overlays can't be applied automatically before
the kernel is started. One option would still be to provide them to
U-Boot and apply a selected overlay based on environment variables.
Another option would be to apply overlays as part of the build process,
which shouldn't require modifying the DT sources to #include the .dtsi
file for the mezzanine board.

> [1] https://github.com/Kevin-WSCU/96Boards-Camera/blob/master/AISTARVISION%20MIPI%20Adapter%20V2.1/AISTARVISION%20MIPI%20Adapter%20V2.1.pdf

-- 
Regards,

Laurent Pinchart

Re: [Query] : DT: Adding mezzanine board

[Lad, Prabhakar]

Hi Laurent,

On Wed, Feb 19, 2020 at 12:08 PM Laurent Pinchart
<laurent.pinchart@ideasonboard.com> wrote:
>
> Hi Prabhakar,
>
> On Wed, Feb 19, 2020 at 11:42:42AM +0000, Lad, Prabhakar wrote:
> > Hi,
> >
> > I am working Renesas RZ/Gx platforms, these boards have support for
> > connecting MIPI adapter mezzanine board [1]. To enable this support I
> > am planning to create a dtsi which will include the board file and
> > enable the necessary VIN/CSI and the camera endpoint.
> >
> > For example: to add support for G2E board I would create a file named
> > r8a774c0-cat874-mipi-adapter.dtsi which will include the board file
> > r8a774c0.dtsi and enable necessary VIN/CSI/Camera endpoint and when
> > user wants to enable this support for the G2E board he could just
> > include r8a774c0-cat874-mipi-adapter.dtsi to r8a774c0-cat874.dts
> >
> > Would this be a good approach or is there an alternative way which I am missing.
>
> DT overlays are another option. They can't be applied on a running
> system though. It doesn't seem like the mezzanine boards can be detected
> by the boot loader, so overlays can't be applied automatically before
> the kernel is started. One option would still be to provide them to
> U-Boot and apply a selected overlay based on environment variables.
> Another option would be to apply overlays as part of the build process,
> which shouldn't require modifying the DT sources to #include the .dtsi
> file for the mezzanine board.
>
Thank you for the insight, overlay is something which I wanted to
avoid and have the
dtb as part of kernel itself.
How about just creating r8a774c0-cat874-mipi-adapter.dts which would
include r8a774c0-cat874.dts
file and enable the VIN/CSI/Camera endpoint, so the user would just
use r8a774c0-cat874-mipi-adapter.dtb
file when the mipi adapter is connected ?

Cheers,
--Prabhakar

> > [1] https://github.com/Kevin-WSCU/96Boards-Camera/blob/master/AISTARVISION%20MIPI%20Adapter%20V2.1/AISTARVISION%20MIPI%20Adapter%20V2.1.pdf
>
> --
> Regards,
>
> Laurent Pinchart

Re: [Query] : DT: Adding mezzanine board

[Laurent Pinchart]

Hi Prabhakar,

On Wed, Feb 19, 2020 at 12:25:37PM +0000, Lad, Prabhakar wrote:
> On Wed, Feb 19, 2020 at 12:08 PM Laurent Pinchart wrote:
> > On Wed, Feb 19, 2020 at 11:42:42AM +0000, Lad, Prabhakar wrote:
> > > Hi,
> > >
> > > I am working Renesas RZ/Gx platforms, these boards have support for
> > > connecting MIPI adapter mezzanine board [1]. To enable this support I
> > > am planning to create a dtsi which will include the board file and
> > > enable the necessary VIN/CSI and the camera endpoint.
> > >
> > > For example: to add support for G2E board I would create a file named
> > > r8a774c0-cat874-mipi-adapter.dtsi which will include the board file
> > > r8a774c0.dtsi and enable necessary VIN/CSI/Camera endpoint and when
> > > user wants to enable this support for the G2E board he could just
> > > include r8a774c0-cat874-mipi-adapter.dtsi to r8a774c0-cat874.dts
> > >
> > > Would this be a good approach or is there an alternative way which I am missing.
> >
> > DT overlays are another option. They can't be applied on a running
> > system though. It doesn't seem like the mezzanine boards can be detected
> > by the boot loader, so overlays can't be applied automatically before
> > the kernel is started. One option would still be to provide them to
> > U-Boot and apply a selected overlay based on environment variables.
> > Another option would be to apply overlays as part of the build process,
> > which shouldn't require modifying the DT sources to #include the .dtsi
> > file for the mezzanine board.
>
> Thank you for the insight, overlay is something which I wanted to
> avoid and have the dtb as part of kernel itself. How about just
> creating r8a774c0-cat874-mipi-adapter.dts which would include
> r8a774c0-cat874.dts file and enable the VIN/CSI/Camera endpoint, so
> the user would just use r8a774c0-cat874-mipi-adapter.dtb file when the
> mipi adapter is connected ?

That would restrict usage of the mezzanine board to a particular base
board, while in the general case there could be different types of base
boards compatible with a set of mezzanines.

The reason why I mentioned overlay isn't really to apply them
dynamically, but for the set of tools around them. Bootloaders can apply
overlays, and we can also apply overlays to a DTB as part of a build
process, without patching the source. Is there a particular reason why
you would prefer avoiding them ?

> > > [1] https://github.com/Kevin-WSCU/96Boards-Camera/blob/master/AISTARVISION%20MIPI%20Adapter%20V2.1/AISTARVISION%20MIPI%20Adapter%20V2.1.pdf

-- 
Regards,

Laurent Pinchart

Re: [Query] : DT: Adding mezzanine board

[Lad, Prabhakar]

Hi Laurent,

On Wed, Feb 19, 2020 at 12:33 PM Laurent Pinchart
<laurent.pinchart@ideasonboard.com> wrote:
>
> Hi Prabhakar,
>
> On Wed, Feb 19, 2020 at 12:25:37PM +0000, Lad, Prabhakar wrote:
> > On Wed, Feb 19, 2020 at 12:08 PM Laurent Pinchart wrote:
> > > On Wed, Feb 19, 2020 at 11:42:42AM +0000, Lad, Prabhakar wrote:
> > > > Hi,
> > > >
> > > > I am working Renesas RZ/Gx platforms, these boards have support for
> > > > connecting MIPI adapter mezzanine board [1]. To enable this support I
> > > > am planning to create a dtsi which will include the board file and
> > > > enable the necessary VIN/CSI and the camera endpoint.
> > > >
> > > > For example: to add support for G2E board I would create a file named
> > > > r8a774c0-cat874-mipi-adapter.dtsi which will include the board file
> > > > r8a774c0.dtsi and enable necessary VIN/CSI/Camera endpoint and when
> > > > user wants to enable this support for the G2E board he could just
> > > > include r8a774c0-cat874-mipi-adapter.dtsi to r8a774c0-cat874.dts
> > > >
> > > > Would this be a good approach or is there an alternative way which I am missing.
> > >
> > > DT overlays are another option. They can't be applied on a running
> > > system though. It doesn't seem like the mezzanine boards can be detected
> > > by the boot loader, so overlays can't be applied automatically before
> > > the kernel is started. One option would still be to provide them to
> > > U-Boot and apply a selected overlay based on environment variables.
> > > Another option would be to apply overlays as part of the build process,
> > > which shouldn't require modifying the DT sources to #include the .dtsi
> > > file for the mezzanine board.
> >
> > Thank you for the insight, overlay is something which I wanted to
> > avoid and have the dtb as part of kernel itself. How about just
> > creating r8a774c0-cat874-mipi-adapter.dts which would include
> > r8a774c0-cat874.dts file and enable the VIN/CSI/Camera endpoint, so
> > the user would just use r8a774c0-cat874-mipi-adapter.dtb file when the
> > mipi adapter is connected ?
>
> That would restrict usage of the mezzanine board to a particular base
> board, while in the general case there could be different types of base
> boards compatible with a set of mezzanines.
>
> The reason why I mentioned overlay isn't really to apply them
> dynamically, but for the set of tools around them. Bootloaders can apply
> overlays, and we can also apply overlays to a DTB as part of a build
> process, without patching the source. Is there a particular reason why
> you would prefer avoiding them ?
>
Just didnt wanted to maintain to the DT overlay separately, but looks like
overlay itself would be a way to go.

Thank you for the inputs.

Cheers,
--Prabhakar

> > > > [1] https://github.com/Kevin-WSCU/96Boards-Camera/blob/master/AISTARVISION%20MIPI%20Adapter%20V2.1/AISTARVISION%20MIPI%20Adapter%20V2.1.pdf
>
> --
> Regards,
>
> Laurent Pinchart