[PATCH/RFC,02/12] dt-bindings: display: renesas: lvds: Document renesas,swap-data
diff mbox series

Message ID 1564731249-22671-3-git-send-email-fabrizio.castro@bp.renesas.com
State Superseded
Delegated to: Kieran Bingham
Headers show
Series
  • Add dual-LVDS panel support to EK874
Related show

Commit Message

Fabrizio Castro Aug. 2, 2019, 7:33 a.m. UTC
R-Car D3, R-Car E3, and RZ/G2E support dual-link mode.
In such a mode, the first LVDS encoder emits even data, and the
second LVDS encoder emits odd data. This patch documents property
renesas,swap-data, used to swap even and odd data around.

Signed-off-by: Fabrizio Castro <fabrizio.castro@bp.renesas.com>
---
 Documentation/devicetree/bindings/display/bridge/renesas,lvds.txt | 5 +++++
 1 file changed, 5 insertions(+)

Comments

Laurent Pinchart Aug. 2, 2019, 7:44 a.m. UTC | #1
Hi Fabrizio,

Thank you for the patch.

On Fri, Aug 02, 2019 at 08:33:59AM +0100, Fabrizio Castro wrote:
> R-Car D3, R-Car E3, and RZ/G2E support dual-link mode.
> In such a mode, the first LVDS encoder emits even data, and the
> second LVDS encoder emits odd data. This patch documents property
> renesas,swap-data, used to swap even and odd data around.
> 
> Signed-off-by: Fabrizio Castro <fabrizio.castro@bp.renesas.com>
> ---
>  Documentation/devicetree/bindings/display/bridge/renesas,lvds.txt | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/display/bridge/renesas,lvds.txt b/Documentation/devicetree/bindings/display/bridge/renesas,lvds.txt
> index dece79e..8980179 100644
> --- a/Documentation/devicetree/bindings/display/bridge/renesas,lvds.txt
> +++ b/Documentation/devicetree/bindings/display/bridge/renesas,lvds.txt
> @@ -52,6 +52,11 @@ Optional properties:
>    mandatory for the first LVDS encoder on R-Car D3, R-Car E3, and RZ/G2E SoCs,
>    and shall point to the second encoder to be used as a companion in dual-link
>    mode. It shall not be set for any other LVDS encoder.
> +- renesas,swap-data : when in dual-link mode, the first LVDS encoder normally
> +  emits even data, and the second LVDS encoder emits odd data. When property
> +  renesas,swap-data is specified, the data emitted by the two encoders will be
> +  swapped around. This property can only be used in conjunction with property
> +  renesas,companion.

From an LVDS encoder point of view this is more a configuration option
than a description of the hardware. Wouldn't it be better for the LVDS
sink to report which of the odd or even pixels it expects on each of its
endpoints ? The LVDS encoder driver could then query that at runtime and
configure itself accordingly. Ideally this should be queried through the
drm_bridge_timings structure (or through a similar mean), not through
DT. An LVDS sink that has a fixed mapping of odd/even pixels to
endpoints wouldn't need the information to be specified in DT at all.

>  
>  
>  Example:
Fabrizio Castro Aug. 5, 2019, 8:59 a.m. UTC | #2
Hi Laurent,

Thank you for your feedback!

> From: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> Sent: 02 August 2019 08:44
> Subject: Re: [PATCH/RFC 02/12] dt-bindings: display: renesas: lvds: Document renesas,swap-data
> 
> Hi Fabrizio,
> 
> Thank you for the patch.
> 
> On Fri, Aug 02, 2019 at 08:33:59AM +0100, Fabrizio Castro wrote:
> > R-Car D3, R-Car E3, and RZ/G2E support dual-link mode.
> > In such a mode, the first LVDS encoder emits even data, and the
> > second LVDS encoder emits odd data. This patch documents property
> > renesas,swap-data, used to swap even and odd data around.
> >
> > Signed-off-by: Fabrizio Castro <fabrizio.castro@bp.renesas.com>
> > ---
> >  Documentation/devicetree/bindings/display/bridge/renesas,lvds.txt | 5 +++++
> >  1 file changed, 5 insertions(+)
> >
> > diff --git a/Documentation/devicetree/bindings/display/bridge/renesas,lvds.txt
> b/Documentation/devicetree/bindings/display/bridge/renesas,lvds.txt
> > index dece79e..8980179 100644
> > --- a/Documentation/devicetree/bindings/display/bridge/renesas,lvds.txt
> > +++ b/Documentation/devicetree/bindings/display/bridge/renesas,lvds.txt
> > @@ -52,6 +52,11 @@ Optional properties:
> >    mandatory for the first LVDS encoder on R-Car D3, R-Car E3, and RZ/G2E SoCs,
> >    and shall point to the second encoder to be used as a companion in dual-link
> >    mode. It shall not be set for any other LVDS encoder.
> > +- renesas,swap-data : when in dual-link mode, the first LVDS encoder normally
> > +  emits even data, and the second LVDS encoder emits odd data. When property
> > +  renesas,swap-data is specified, the data emitted by the two encoders will be
> > +  swapped around. This property can only be used in conjunction with property
> > +  renesas,companion.
> 
> From an LVDS encoder point of view this is more a configuration option
> than a description of the hardware. Wouldn't it be better for the LVDS
> sink to report which of the odd or even pixels it expects on each of its
> endpoints ?

Yes, that would be my preference too, and it would be better, I am just not entirely
what's the best place for this information though

> The LVDS encoder driver could then query that at runtime and
> configure itself accordingly. Ideally this should be queried through the
> drm_bridge_timings structure (or through a similar mean), not through
> DT. An LVDS sink that has a fixed mapping of odd/even pixels to
> endpoints wouldn't need the information to be specified in DT at all.

Isn't drm_bridge_timings specific for bridges?

Thanks!
Fab

> 
> >
> >
> >  Example:
> 
> --
> Regards,
> 
> Laurent Pinchart
Laurent Pinchart Aug. 5, 2019, 9:35 a.m. UTC | #3
Hi Fabrizio,

On Mon, Aug 05, 2019 at 08:59:51AM +0000, Fabrizio Castro wrote:
> > From: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> > Sent: 02 August 2019 08:44
> > Subject: Re: [PATCH/RFC 02/12] dt-bindings: display: renesas: lvds: Document renesas,swap-data
> > 
> > Hi Fabrizio,
> > 
> > Thank you for the patch.
> > 
> > On Fri, Aug 02, 2019 at 08:33:59AM +0100, Fabrizio Castro wrote:
> > > R-Car D3, R-Car E3, and RZ/G2E support dual-link mode.
> > > In such a mode, the first LVDS encoder emits even data, and the
> > > second LVDS encoder emits odd data. This patch documents property
> > > renesas,swap-data, used to swap even and odd data around.
> > >
> > > Signed-off-by: Fabrizio Castro <fabrizio.castro@bp.renesas.com>
> > > ---
> > >  Documentation/devicetree/bindings/display/bridge/renesas,lvds.txt | 5 +++++
> > >  1 file changed, 5 insertions(+)
> > >
> > > diff --git a/Documentation/devicetree/bindings/display/bridge/renesas,lvds.txt
> > b/Documentation/devicetree/bindings/display/bridge/renesas,lvds.txt
> > > index dece79e..8980179 100644
> > > --- a/Documentation/devicetree/bindings/display/bridge/renesas,lvds.txt
> > > +++ b/Documentation/devicetree/bindings/display/bridge/renesas,lvds.txt
> > > @@ -52,6 +52,11 @@ Optional properties:
> > >    mandatory for the first LVDS encoder on R-Car D3, R-Car E3, and RZ/G2E SoCs,
> > >    and shall point to the second encoder to be used as a companion in dual-link
> > >    mode. It shall not be set for any other LVDS encoder.
> > > +- renesas,swap-data : when in dual-link mode, the first LVDS encoder normally
> > > +  emits even data, and the second LVDS encoder emits odd data. When property
> > > +  renesas,swap-data is specified, the data emitted by the two encoders will be
> > > +  swapped around. This property can only be used in conjunction with property
> > > +  renesas,companion.
> > 
> > From an LVDS encoder point of view this is more a configuration option
> > than a description of the hardware. Wouldn't it be better for the LVDS
> > sink to report which of the odd or even pixels it expects on each of its
> > endpoints ?
> 
> Yes, that would be my preference too, and it would be better, I am just not entirely
> what's the best place for this information though
> 
> > The LVDS encoder driver could then query that at runtime and
> > configure itself accordingly. Ideally this should be queried through the
> > drm_bridge_timings structure (or through a similar mean), not through
> > DT. An LVDS sink that has a fixed mapping of odd/even pixels to
> > endpoints wouldn't need the information to be specified in DT at all.
> 
> Isn't drm_bridge_timings specific for bridges?

Its name makes it specific to bridges, but the information it contains
could equally apply to panels. I would thus use it for both, possibly
after renaming it.
Fabrizio Castro Aug. 5, 2019, 10:07 a.m. UTC | #4
Hi Laurent,

> From: linux-kernel-owner@vger.kernel.org <linux-kernel-owner@vger.kernel.org> On Behalf Of Laurent Pinchart
> Sent: 05 August 2019 10:36
> Subject: Re: [PATCH/RFC 02/12] dt-bindings: display: renesas: lvds: Document renesas,swap-data
> 
> Hi Fabrizio,
> 
> On Mon, Aug 05, 2019 at 08:59:51AM +0000, Fabrizio Castro wrote:
> > > From: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> > > Sent: 02 August 2019 08:44
> > > Subject: Re: [PATCH/RFC 02/12] dt-bindings: display: renesas: lvds: Document renesas,swap-data
> > >
> > > Hi Fabrizio,
> > >
> > > Thank you for the patch.
> > >
> > > On Fri, Aug 02, 2019 at 08:33:59AM +0100, Fabrizio Castro wrote:
> > > > R-Car D3, R-Car E3, and RZ/G2E support dual-link mode.
> > > > In such a mode, the first LVDS encoder emits even data, and the
> > > > second LVDS encoder emits odd data. This patch documents property
> > > > renesas,swap-data, used to swap even and odd data around.
> > > >
> > > > Signed-off-by: Fabrizio Castro <fabrizio.castro@bp.renesas.com>
> > > > ---
> > > >  Documentation/devicetree/bindings/display/bridge/renesas,lvds.txt | 5 +++++
> > > >  1 file changed, 5 insertions(+)
> > > >
> > > > diff --git a/Documentation/devicetree/bindings/display/bridge/renesas,lvds.txt
> > > b/Documentation/devicetree/bindings/display/bridge/renesas,lvds.txt
> > > > index dece79e..8980179 100644
> > > > --- a/Documentation/devicetree/bindings/display/bridge/renesas,lvds.txt
> > > > +++ b/Documentation/devicetree/bindings/display/bridge/renesas,lvds.txt
> > > > @@ -52,6 +52,11 @@ Optional properties:
> > > >    mandatory for the first LVDS encoder on R-Car D3, R-Car E3, and RZ/G2E SoCs,
> > > >    and shall point to the second encoder to be used as a companion in dual-link
> > > >    mode. It shall not be set for any other LVDS encoder.
> > > > +- renesas,swap-data : when in dual-link mode, the first LVDS encoder normally
> > > > +  emits even data, and the second LVDS encoder emits odd data. When property
> > > > +  renesas,swap-data is specified, the data emitted by the two encoders will be
> > > > +  swapped around. This property can only be used in conjunction with property
> > > > +  renesas,companion.
> > >
> > > From an LVDS encoder point of view this is more a configuration option
> > > than a description of the hardware. Wouldn't it be better for the LVDS
> > > sink to report which of the odd or even pixels it expects on each of its
> > > endpoints ?
> >
> > Yes, that would be my preference too, and it would be better, I am just not entirely
> > what's the best place for this information though
> >
> > > The LVDS encoder driver could then query that at runtime and
> > > configure itself accordingly. Ideally this should be queried through the
> > > drm_bridge_timings structure (or through a similar mean), not through
> > > DT. An LVDS sink that has a fixed mapping of odd/even pixels to
> > > endpoints wouldn't need the information to be specified in DT at all.
> >
> > Isn't drm_bridge_timings specific for bridges?
> 
> Its name makes it specific to bridges, but the information it contains
> could equally apply to panels. I would thus use it for both, possibly
> after renaming it.

Will give this a try then.

Thanks,
Fab

> 
> --
> Regards,
> 
> Laurent Pinchart

Patch
diff mbox series

diff --git a/Documentation/devicetree/bindings/display/bridge/renesas,lvds.txt b/Documentation/devicetree/bindings/display/bridge/renesas,lvds.txt
index dece79e..8980179 100644
--- a/Documentation/devicetree/bindings/display/bridge/renesas,lvds.txt
+++ b/Documentation/devicetree/bindings/display/bridge/renesas,lvds.txt
@@ -52,6 +52,11 @@  Optional properties:
   mandatory for the first LVDS encoder on R-Car D3, R-Car E3, and RZ/G2E SoCs,
   and shall point to the second encoder to be used as a companion in dual-link
   mode. It shall not be set for any other LVDS encoder.
+- renesas,swap-data : when in dual-link mode, the first LVDS encoder normally
+  emits even data, and the second LVDS encoder emits odd data. When property
+  renesas,swap-data is specified, the data emitted by the two encoders will be
+  swapped around. This property can only be used in conjunction with property
+  renesas,companion.
 
 
 Example: