On some HW designs, it's easier for the layout if the P/N pins are swapped.
The driver currently has a DT property to do that.
This change documents the 'lontium,pn-swap' property.
Signed-off-by: Alexandru Ardelean <[email protected]>
---
.../devicetree/bindings/display/bridge/lontium,lt8912b.yaml | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/Documentation/devicetree/bindings/display/bridge/lontium,lt8912b.yaml b/Documentation/devicetree/bindings/display/bridge/lontium,lt8912b.yaml
index 2cef252157985..3a804926b288a 100644
--- a/Documentation/devicetree/bindings/display/bridge/lontium,lt8912b.yaml
+++ b/Documentation/devicetree/bindings/display/bridge/lontium,lt8912b.yaml
@@ -24,6 +24,12 @@ properties:
maxItems: 1
description: GPIO connected to active high RESET pin.
+ lontium,pn-swap:
+ description: Swap the polarities of the P/N pins in software.
+ On some HW designs, the layout is simplified if the P/N pins
+ are inverted.
+ type: boolean
+
ports:
$ref: /schemas/graph.yaml#/properties/ports
--
2.44.0
On Tue, Apr 02, 2024 at 01:59:25PM +0300, Alexandru Ardelean wrote:
> On some HW designs, it's easier for the layout if the P/N pins are swapped.
> The driver currently has a DT property to do that.
"currently", because 1/2 adds it. bindings patches should precede the
driver patches in the series, so please swap the patches and remove this
portion of the description.
>
> This change documents the 'lontium,pn-swap' property.
>
> Signed-off-by: Alexandru Ardelean <[email protected]>
> ---
> .../devicetree/bindings/display/bridge/lontium,lt8912b.yaml | 6 ++++++
> 1 file changed, 6 insertions(+)
>
> diff --git a/Documentation/devicetree/bindings/display/bridge/lontium,lt8912b.yaml b/Documentation/devicetree/bindings/display/bridge/lontium,lt8912b.yaml
> index 2cef252157985..3a804926b288a 100644
> --- a/Documentation/devicetree/bindings/display/bridge/lontium,lt8912b.yaml
> +++ b/Documentation/devicetree/bindings/display/bridge/lontium,lt8912b.yaml
> @@ -24,6 +24,12 @@ properties:
> maxItems: 1
> description: GPIO connected to active high RESET pin.
>
> + lontium,pn-swap:
> + description: Swap the polarities of the P/N pins in software.
> + On some HW designs, the layout is simplified if the P/N pins
> + are inverted.
Please explain what configuration of a board would cause these to be
swapped, rather than why someone might want to configure the board this
way. I've got no idea what this hardware is actually doing, so this is
being pulled out of a hat, but I'd expect something like "Some boards
swap the polarity of the P/N pins, use this property to indicate this to
software".
> + type: boolean
The type here should be flag.
Cheers,
Conor.
> +
> ports:
> $ref: /schemas/graph.yaml#/properties/ports
>
> --
> 2.44.0
>
On Tue, Apr 2, 2024 at 9:06 PM Conor Dooley <[email protected]> wrote:
>
> On Tue, Apr 02, 2024 at 01:59:25PM +0300, Alexandru Ardelean wrote:
> > On some HW designs, it's easier for the layout if the P/N pins are swapped.
> > The driver currently has a DT property to do that.
>
> "currently", because 1/2 adds it. bindings patches should precede the
> driver patches in the series, so please swap the patches and remove this
> portion of the description.
ack;
i'll invert the order and remove this;
>
> >
> > This change documents the 'lontium,pn-swap' property.
> >
> > Signed-off-by: Alexandru Ardelean <[email protected]>
> > ---
> > .../devicetree/bindings/display/bridge/lontium,lt8912b.yaml | 6 ++++++
> > 1 file changed, 6 insertions(+)
> >
> > diff --git a/Documentation/devicetree/bindings/display/bridge/lontium,lt8912b.yaml b/Documentation/devicetree/bindings/display/bridge/lontium,lt8912b.yaml
> > index 2cef252157985..3a804926b288a 100644
> > --- a/Documentation/devicetree/bindings/display/bridge/lontium,lt8912b.yaml
> > +++ b/Documentation/devicetree/bindings/display/bridge/lontium,lt8912b.yaml
> > @@ -24,6 +24,12 @@ properties:
> > maxItems: 1
> > description: GPIO connected to active high RESET pin.
> >
> > + lontium,pn-swap:
> > + description: Swap the polarities of the P/N pins in software.
> > + On some HW designs, the layout is simplified if the P/N pins
> > + are inverted.
>
> Please explain what configuration of a board would cause these to be
> swapped, rather than why someone might want to configure the board this
> way. I've got no idea what this hardware is actually doing, so this is
> being pulled out of a hat, but I'd expect something like "Some boards
> swap the polarity of the P/N pins, use this property to indicate this to
> software".
ack
if it's fine with you, i'll use your suggested description;
for a broader context, we were using a DSI-HDMI converter [1] from
SomLabs on a different (than SomLabs) board;
and we were not seeing anything on the HDMI-connected display;
as I understand it, some DSI-HDMI bridges support P/N auto-inversion;
this one doesn't AFAICT;
on this DSI-HDMI converter [1], we've noticed that the P/N pins were
inverted from the DSI to the chip (vs what we expected to see)
after changing the register value (for the P/N swap), it worked;
our conclusion was that, the design of the converter (board) was done
as-such, because it made the layout easier
[1] https://wiki.somlabs.com/index.php/SL-MIPI-LVDS-HDMI-CNV-11_Datasheet_and_Pinout
>
> > + type: boolean
>
> The type here should be flag.
ack; i'll change the type
>
> Cheers,
> Conor.
>
> > +
> > ports:
> > $ref: /schemas/graph.yaml#/properties/ports
> >
> > --
> > 2.44.0
> >
On Wed, Apr 03, 2024 at 09:16:31AM +0300, Alexandru Ardelean wrote:
> >
> > > + type: boolean
> >
> > The type here should be flag.
>
> ack; i'll change the type
I prob shoulda said, its "$ref: /schemas/types.yaml#/definitions/flag"
instead of "type: boolean".
On Tue, Apr 02, 2024 at 01:59:25PM +0300, Alexandru Ardelean wrote:
> On some HW designs, it's easier for the layout if the P/N pins are swapped.
> The driver currently has a DT property to do that.
>
> This change documents the 'lontium,pn-swap' property.
>
> Signed-off-by: Alexandru Ardelean <[email protected]>
> ---
> .../devicetree/bindings/display/bridge/lontium,lt8912b.yaml | 6 ++++++
> 1 file changed, 6 insertions(+)
>
> diff --git a/Documentation/devicetree/bindings/display/bridge/lontium,lt8912b.yaml b/Documentation/devicetree/bindings/display/bridge/lontium,lt8912b.yaml
> index 2cef252157985..3a804926b288a 100644
> --- a/Documentation/devicetree/bindings/display/bridge/lontium,lt8912b.yaml
> +++ b/Documentation/devicetree/bindings/display/bridge/lontium,lt8912b.yaml
> @@ -24,6 +24,12 @@ properties:
> maxItems: 1
> description: GPIO connected to active high RESET pin.
>
> + lontium,pn-swap:
> + description: Swap the polarities of the P/N pins in software.
> + On some HW designs, the layout is simplified if the P/N pins
> + are inverted.
> + type: boolean
> +
I'd like to point out the standard `lane-polarities` property defined at
Documentation/devicetree/bindings/media/video-interfaces.yaml. You can
define and use it for the corresponding endpoint in the lt8912b schema.
> ports:
> $ref: /schemas/graph.yaml#/properties/ports
>
> --
> 2.44.0
>
--
With best wishes
Dmitry
On Sun, Apr 7, 2024 at 11:31 PM Dmitry Baryshkov
<[email protected]> wrote:
>
> On Tue, Apr 02, 2024 at 01:59:25PM +0300, Alexandru Ardelean wrote:
> > On some HW designs, it's easier for the layout if the P/N pins are swapped.
> > The driver currently has a DT property to do that.
> >
> > This change documents the 'lontium,pn-swap' property.
> >
> > Signed-off-by: Alexandru Ardelean <[email protected]>
> > ---
> > .../devicetree/bindings/display/bridge/lontium,lt8912b.yaml | 6 ++++++
> > 1 file changed, 6 insertions(+)
> >
> > diff --git a/Documentation/devicetree/bindings/display/bridge/lontium,lt8912b.yaml b/Documentation/devicetree/bindings/display/bridge/lontium,lt8912b.yaml
> > index 2cef252157985..3a804926b288a 100644
> > --- a/Documentation/devicetree/bindings/display/bridge/lontium,lt8912b.yaml
> > +++ b/Documentation/devicetree/bindings/display/bridge/lontium,lt8912b.yaml
> > @@ -24,6 +24,12 @@ properties:
> > maxItems: 1
> > description: GPIO connected to active high RESET pin.
> >
> > + lontium,pn-swap:
> > + description: Swap the polarities of the P/N pins in software.
> > + On some HW designs, the layout is simplified if the P/N pins
> > + are inverted.
> > + type: boolean
> > +
>
> I'd like to point out the standard `lane-polarities` property defined at
> Documentation/devicetree/bindings/media/video-interfaces.yaml. You can
> define and use it for the corresponding endpoint in the lt8912b schema.
>
Ohhh.
Interesting :)
Many thanks for pointing this out.
This will make things much easier.
Will do a V2 with this in a week or two.
I'm traveling now.
Thanks
Alex
> > ports:
> > $ref: /schemas/graph.yaml#/properties/ports
> >
> > --
> > 2.44.0
> >
>
> --
> With best wishes
> Dmitry