Re: [PATCH 1/7] dt-bindings: display/msm/dsi: allow specifying TE source

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On 5/22/2024 1:05 PM, Dmitry Baryshkov wrote:
On Wed, 22 May 2024 at 21:38, Abhinav Kumar <quic_abhinavk@xxxxxxxxxxx> wrote:



On 5/20/2024 5:12 AM, Dmitry Baryshkov wrote:
Command mode panels provide TE signal back to the DSI host to signal
that the frame display has completed and update of the image will not
cause tearing. Usually it is connected to the first GPIO with the
mdp_vsync function, which is the default. In such case the property can
be skipped.


This is a good addition overall. Some comments below.

Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxx>
---
   .../bindings/display/msm/dsi-controller-main.yaml        | 16 ++++++++++++++++
   1 file changed, 16 insertions(+)

diff --git a/Documentation/devicetree/bindings/display/msm/dsi-controller-main.yaml b/Documentation/devicetree/bindings/display/msm/dsi-controller-main.yaml
index 1fa28e976559..c1771c69b247 100644
--- a/Documentation/devicetree/bindings/display/msm/dsi-controller-main.yaml
+++ b/Documentation/devicetree/bindings/display/msm/dsi-controller-main.yaml
@@ -162,6 +162,21 @@ properties:
                   items:
                     enum: [ 0, 1, 2, 3 ]

+              qcom,te-source:
+                $ref: /schemas/types.yaml#/definitions/string
+                description:
+                  Specifies the source of vsync signal from the panel used for
+                  tearing elimination. The default is mdp_gpio0.

panel --> command mode panel?

+                enum:
+                  - mdp_gpio0
+                  - mdp_gpio1
+                  - mdp_gpio2

are gpio0, gpio1 and gpio2 referring to the vsync_p, vsync_s and vsync_e
sources?

No idea, unfortunately. They are gpioN or just mdp_vsync all over the
place. For the reference, in case of the SDM845 and Pixel3 the signal
is routed through SoC GPIO12.


GPIO12 on sdm845 is mdp_vsync_e.

Thats why I think its better we use mdp_vsync_p/s/e instead of mdp_gpio0/1/2

In that case wouldnt it be better to name it like that?

+                  - timer0
+                  - timer1
+                  - timer2
+                  - timer3
+                  - timer4
+

These are indicating watchdog timer sources right?

Yes.


       required:
         - port@0
         - port@1
@@ -452,6 +467,7 @@ examples:
                             dsi0_out: endpoint {
                                      remote-endpoint = <&sn65dsi86_in>;
                                      data-lanes = <0 1 2 3>;
+                                   qcom,te-source = "mdp_gpio2";

I have a basic doubt on this. Should te-source should be in the input
port or the output one for the controller? Because TE is an input to the
DSI. And if the source is watchdog timer then it aligns even more as a
property of the input endpoint.

I don't really want to split this. Both data-lanes and te-source are
properties of the link between the DSI and panel. You can not really
say which side has which property.


TE is an input to the DSI from the panel. Between input and output port, I think it belongs more to the input port.

I didnt follow why this is a link property. Sorry , I didnt follow the split part.

If we are unsure about input vs output port, do you think its better we make it a property of the main dsi node instead?

                             };
                     };
              };





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