On Mon 24 May 02:30 CDT 2021, Vinod Koul wrote:

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

quoted

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

In the case of DP there's bits to be read in the panel to figure this
out, for DSI panels this seems like a property that the panel (driver)
should know about.

2. Host needs to support it

Right, so this needs to be known by the driver. My suggestion is that we
derive it from the compatible or from the HW version.

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 :)

Can we describe those cases? E.g. is it because enabling DSC would not
cause a reduction in clock speed that's worth the effort? Or do we only
use DSC for DSI when it allows us to squeeze everything into a single
link?

Regards,
Bjorn

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

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