On 21-05-21, 09:42, Bjorn Andersson wrote:

On Fri 21 May 07:49 CDT 2021, Vinod Koul wrote:

quoted

DSC enables streams to be compressed before we send to panel. This
requires DSC enabled encoder and a panel to be present. So we add this
information in board DTS and find if DSC can be enabled and the
parameters required to configure DSC are added to binding document along
with example

Signed-off-by: Vinod Koul <vkoul@kernel.org>
---
 .../devicetree/bindings/display/msm/dsi.txt       | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/Documentation/devicetree/bindings/display/msm/dsi.txt b/Documentation/devicetree/bindings/display/msm/dsi.txt
index b9a64d3ff184..83d2fb92267e 100644
--- a/Documentation/devicetree/bindings/display/msm/dsi.txt
+++ b/Documentation/devicetree/bindings/display/msm/dsi.txt

@@ -48,6 +48,13 @@ Optional properties:
 - pinctrl-n: the "sleep" pinctrl state
 - ports: contains DSI controller input and output ports as children, each
   containing one endpoint subnode.
+- qcom,mdss-dsc-enabled: Display Stream Compression (DSC) is enabled
+- qcom,mdss-slice-height: DSC slice height in pixels
+- qcom,mdss-slice-width: DSC slice width in pixels
+- qcom,mdss-slice-per-pkt: DSC slices per packet
+- qcom,mdss-bit-per-component: DSC bits per component
+- qcom,mdss-bit-per-pixel: DSC bits per pixel
+- qcom,mdss-block-prediction-enable: Block prediction mode of DSC enabled
 
   DSI Endpoint properties:
   - remote-endpoint: For port@0, set to phandle of the connected panel/bridge's

@@ -188,6 +195,14 @@ Example:
 		qcom,master-dsi;
 		qcom,sync-dual-dsi;
 
+		qcom,mdss-dsc-enabled;

To me the activation of DSC seems to be a property of the panel.

I think there are three parts to the problem
1. Panel needs to support it
2. Host needs to support it
3. Someone needs to decide to use when both the above conditions are
met.

There are cases where above 1, 2 will be satisfied, but we might be okay
without DSC too.. so how to decide when to do DSC :)

I feel it is more of a system property. And I also think that these
parameters here are host configuration and not really for panel...

quoted

+		qcom,mdss-slice-height = <16>;
+		qcom,mdss-slice-width = <540>;
+		qcom,mdss-slice-per-pkt = <1>;
+		qcom,mdss-bit-per-component = <8>;
+		qcom,mdss-bit-per-pixel = <8>;
+		qcom,mdss-block-prediction-enable;

Which of these properties relates to the DSC encoder and what needs to
be agreed with the sink? Can't we derive e.g. bpp from the information
we have from the attached panel already?

Let me go back and check on this a bit more

Thanks
-- 
~Vinod