Hi Laurent,
On 2021-11-10 17:25:54 +0200, Laurent Pinchart wrote:
> Hi Niklas,
>
> On Wed, Oct 20, 2021 at 10:02:22PM +0200, Niklas Söderlund wrote:
> > Hello,
> >
> > This series attempts to increase the flexibility of the R-Car VIN
> > capture pipeline by allowing for free form Virtual Channel routing
> > within the same CSI-2 IP block.
> >
> > When Gen3 support was first added to this R-Car VIN and CSI-2 driver the
> > routing was centred around the CHSEL register which multiplex the
> > different parallel buses that sits between the CSI-2 receivers source
> > side and the VIN dma engines. This was a bad design as the multiplexing
> > do allow for only a few combinations and do not play nice with many
> > video streams in the system.
> >
> > For example it's only possible for CSI-2 Virtual Channels 0 and 1 of any
> > given CSI-2 receiver to be used together with the scaler.
> >
> > Later datasheets have expanded the documentation and it is now possible
> > to improve on this design by allowing any Virtual Channel to be routed
> > to any R-Car VIN instance, provided that there exists a parallel bus
> > between them. This increases the flexibility as all Virtual Channels can
> > now be used together with the scaler for example.
> >
> > The redesign is not however perfect. While the new design allows for
> > many more routes, two constrains limit a small portion of routes that
> > was possible in the old design but are no more.
> >
> > - It is no longer possible to route the same CSI-2 and VC to more then
> > one VIN at a time. This was theoretically possible before if the
> > specific SoC allowed for the same CSI-2 and VC to be routed to two
> > different VIN capture groups.
>
> Does it mean we can't capture image data and embedded data from the same
> camera sensor in separate buffers ?
On the contrary. Without this change we can't capture any embedded data.
With this patch we still can't capture it, unless the R-Car CSI-2
receiver lies. But with this applied we are closer to enable meta data
to reach user space.
>
> > - It is no longer possible to simultaneously mix links from two CSI-2 IP
> > blocks to the same VIN capture group.
> >
> > For example if VIN2 is capturing from CSI40 then VIN{0,1,3} must also
> > capture from CSI40. While VIN{4,5,6,7} is still free to capture from
> > any other CSI-2 IP in the system. Once all VIN{0,1,2,3} links to CSI40
> > are disabled that VIN capture group is free again to capture from any
> > other CSI-2 IP it is connected to.
>
> What practical limitation does this bring, does it forbid any useful use
> case ?
Yes and no ;-). It limits a small set of use-cases, while enabling a
great many more. In the old setup you are allowed to route a mix of Rx
to Tx intermixing a few of the modules 1:1 as an exception. With this
change you get routing n:to:n with a few exceptions.
>
> > At the core of the redesign is greater cooperator of the R-Car VIN and
> > CSI-2 drivers in configuring the routing. The VIN driver is after this
> > change only responsible to configure the full VIN capture groups
> > parallel buses to be to a particular CSI-2 IP. While the configuration
> > of which CSI-2 Virtual Channel is outputted on which of the R-Car CSI-2
> > IP output ports is handled by the CSI-2 driver.
> >
> > Before this change the CSI-2 Virtual Channel to output port was static
> > in the CSI-2 driver and the different links only manipulated the VIN
> > capture groups CHSEL register. With this change both the CHSEl register
> > and the CSI-2 routing VCDT registers are modified for greater
> > flexibility.
> >
> > Patch 1/3 and 2/3 are cleanup patches moving code around preparing for
> > the real work in 3/3. The work is based on the latest media-tree.
> >
> > Kind Regards,
> > Niklas Söderlund
> >
> > Niklas Söderlund (3):
> > media: rcar-vin: Refactor link notify
> > media: rcar-vin: Breakout media link creation
> > media: rcar-{csi2,vin}: Move to full Virtual Channel routing per CSI-2
> > IP
> >
> > drivers/media/platform/rcar-vin/rcar-core.c | 379 ++++++--------------
> > drivers/media/platform/rcar-vin/rcar-csi2.c | 58 ++-
> > drivers/media/platform/rcar-vin/rcar-dma.c | 2 +-
> > drivers/media/platform/rcar-vin/rcar-vin.h | 18 +-
> > 4 files changed, 167 insertions(+), 290 deletions(-)
>
> --
> Regards,
>
> Laurent Pinchart
--
Kind Regards,
Niklas Söderlund
