Re: LVDS panel compatible strings

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On Fri, Jul 14, 2023 at 06:57:01PM +0300, Svyatoslav Ryhel wrote:
> пт, 14 лип. 2023 р. о 18:16 Thierry Reding <thierry.reding@xxxxxxxxx> пише:
> >
> > On Fri, Jul 14, 2023 at 06:00:43PM +0300, Svyatoslav Ryhel wrote:
> > > пт, 14 лип. 2023 р. о 17:38 Thierry Reding <thierry.reding@xxxxxxxxx> пише:
> > > >
> > > > Hi everyone,
> > > >
> > > > I've been working on converting all Tegra-related device tree bindings
> > > > to json-schema so that eventually we can fully validate device tree
> > > > files. Getting all the bindings reviewed and merged has been slow, but
> > > > I have a local tree where pretty much all validation errors and warnings
> > > > have been fixed. The remaining warnings that I'm not sure how to resolve
> > > > are these:
> > > >
> > > >     arch/arm/boot/dts/nvidia/tegra30-asus-nexus7-tilapia-E1565.dtb: display-panel: compatible:0: 'panel-lvds' is not one of ['auo,b101ew05', 'tbs,a711-panel']
> > > >         from schema $id: http://devicetree.org/schemas/display/panel/panel-lvds.yaml#
> > > >     arch/arm/boot/dts/nvidia/tegra30-asus-nexus7-tilapia-E1565.dtb: display-panel: compatible: ['panel-lvds'] is too short
> > > >         from schema $id: http://devicetree.org/schemas/display/panel/panel-lvds.yaml#
> > > >     arch/arm/boot/dts/nvidia/tegra30-asus-nexus7-tilapia-E1565.dtb: display-panel: Unevaluated properties are not allowed ('compatible' was unexpected)
> > > >         from schema $id: http://devicetree.org/schemas/display/panel/panel-lvds.yaml#
> > > >     arch/arm/boot/dts/nvidia/tegra30-asus-nexus7-grouper-E1565.dtb: display-panel: compatible:0: 'panel-lvds' is not one of ['auo,b101ew05', 'tbs,a711-panel']
> > > >         from schema $id: http://devicetree.org/schemas/display/panel/panel-lvds.yaml#
> > > >     arch/arm/boot/dts/nvidia/tegra30-asus-nexus7-grouper-E1565.dtb: display-panel: compatible: ['panel-lvds'] is too short
> > > >         from schema $id: http://devicetree.org/schemas/display/panel/panel-lvds.yaml#
> > > >     arch/arm/boot/dts/nvidia/tegra30-asus-nexus7-grouper-E1565.dtb: display-panel: Unevaluated properties are not allowed ('compatible' was unexpected)
> > > >         from schema $id: http://devicetree.org/schemas/display/panel/panel-lvds.yaml#
> > > >     arch/arm/boot/dts/nvidia/tegra30-asus-nexus7-grouper-PM269.dtb: display-panel: compatible:0: 'panel-lvds' is not one of ['auo,b101ew05', 'tbs,a711-panel']
> > > >         from schema $id: http://devicetree.org/schemas/display/panel/panel-lvds.yaml#
> > > >     arch/arm/boot/dts/nvidia/tegra30-asus-nexus7-grouper-PM269.dtb: display-panel: compatible: ['panel-lvds'] is too short
> > > >         from schema $id: http://devicetree.org/schemas/display/panel/panel-lvds.yaml#
> > > >     arch/arm/boot/dts/nvidia/tegra30-asus-nexus7-grouper-PM269.dtb: display-panel: Unevaluated properties are not allowed ('compatible' was unexpected)
> > > >         from schema $id: http://devicetree.org/schemas/display/panel/panel-lvds.yaml#
> > > >     arch/arm/boot/dts/nvidia/tegra30-pegatron-chagall.dtb: display-panel: compatible:0: 'panel-lvds' is not one of ['auo,b101ew05', 'tbs,a711-panel']
> > > >         from schema $id: http://devicetree.org/schemas/display/panel/panel-lvds.yaml#
> > > >     arch/arm/boot/dts/nvidia/tegra30-pegatron-chagall.dtb: display-panel: compatible: ['panel-lvds'] is too short
> > > >         from schema $id: http://devicetree.org/schemas/display/panel/panel-lvds.yaml#
> > > >     arch/arm/boot/dts/nvidia/tegra30-pegatron-chagall.dtb: display-panel: Unevaluated properties are not allowed ('compatible' was unexpected)
> > > >         from schema $id: http://devicetree.org/schemas/display/panel/panel-lvds.yaml#
> > >
> > > Hello Thierry! Pegatron Chagall uses a Hannstar similar to one used in
> > > ASUS TF201 but unfortunately it is not compatible with existing simple
> > > panel setup (blurry image if used). My assumption is that chagall as
> > > different revision of this panel like HSD101PWW3-B00 or
> > > HSD101PWW1-A00 which is more likely or panel is highly modified which
> > > is unlikely. I propose to use "hannstar,hsd101pww1" which is more wide
> > > spread.
> >
> > Interesting. So is the problem the HSD101PWW2 timings that are off, or
> > is it because the panel-lvds code does something special to make this
> > blurry image go away?
> >
> timings are different

For cases where the timings are the only things that differ, the DT
bindings allow overriding the timings specifically. So you might get
away with using one of the existing panels if it is close enough and
patch up the timings in DT.

Comparing what you've got for Chagall, the porches exceed what the
HSD101PWW2 allows, but the timing values in the simple-panel driver look
a little arbitrary, to be honest, so I think those could be extended.
Looking at a datasheet that I found online, it's very unspecific about
the porch lengths since it only mentions minimum, typical and maximum
values for the total frame blanking times:

	vertical: 3, 23, 223
	horizontal: 54, 160, 681

So I think we can be more generous in how these are split up. So we
could for example do this:

--- >8 ---
diff --git a/drivers/gpu/drm/panel/panel-simple.c b/drivers/gpu/drm/panel/panel-simple.c
index 18dc251749fb..b2fb7943f2ed 100644
--- a/drivers/gpu/drm/panel/panel-simple.c
+++ b/drivers/gpu/drm/panel/panel-simple.c
@@ -2108,13 +2108,13 @@ static const struct panel_desc hannstar_hsd100pxn1 = {
 static const struct display_timing hannstar_hsd101pww2_timing = {
 	.pixelclock = { 64300000, 71100000, 82000000 },
 	.hactive = { 1280, 1280, 1280 },
-	.hfront_porch = { 1, 1, 10 },
-	.hback_porch = { 1, 1, 10 },
-	.hsync_len = { 58, 158, 661 },
+	.hfront_porch = { 1, 1, 64 },
+	.hback_porch = { 1, 1, 64 },
+	.hsync_len = { 58, 158, 553 },
 	.vactive = { 800, 800, 800 },
-	.vfront_porch = { 1, 1, 10 },
-	.vback_porch = { 1, 1, 10 },
-	.vsync_len = { 1, 21, 203 },
+	.vfront_porch = { 1, 1, 32 },
+	.vback_porch = { 1, 1, 32 },
+	.vsync_len = { 1, 21, 159 },
 	.flags = DISPLAY_FLAGS_DE_HIGH,
 };
 
--- >8 ---

And then we could move the compatible string from simple to LVDS:

--- >8 ---
diff --git a/Documentation/devicetree/bindings/display/panel/panel-lvds.yaml b/Documentation/devicetree/bindings/display/panel/panel-lvds.yaml
index 929fe046d1e7..344e5df40c2f 100644
--- a/Documentation/devicetree/bindings/display/panel/panel-lvds.yaml
+++ b/Documentation/devicetree/bindings/display/panel/panel-lvds.yaml
@@ -40,6 +40,8 @@ properties:
     items:
       - enum:
           - auo,b101ew05
+          # HannStar Display Corp. HSD101PWW2 10.1" WXGA (1280x800) LVDS panel
+          - hannstar,hsd101pww2
           - tbs,a711-panel
 
       - const: panel-lvds
diff --git a/Documentation/devicetree/bindings/display/panel/panel-simple.yaml b/Documentation/devicetree/bindings/display/panel/panel-simple.yaml
index df1cec8fd21b..f4d9da4afefd 100644
--- a/Documentation/devicetree/bindings/display/panel/panel-simple.yaml
+++ b/Documentation/devicetree/bindings/display/panel/panel-simple.yaml
@@ -168,8 +168,6 @@ properties:
       - hannstar,hsd070pww1
         # HannStar Display Corp. HSD100PXN1 10.1" XGA LVDS panel
       - hannstar,hsd100pxn1
-        # HannStar Display Corp. HSD101PWW2 10.1" WXGA (1280x800) LVDS panel
-      - hannstar,hsd101pww2
         # Hitachi Ltd. Corporation 9" WVGA (800x480) TFT LCD panel
       - hit,tx23d38vm0caa
         # InfoVision Optoelectronics M133NWF4 R0 13.3" FHD (1920x1080) TFT LCD panel
diff --git a/arch/arm/boot/dts/nvidia/tegra30-pegatron-chagall.dts b/arch/arm/boot/dts/nvidia/tegra30-pegatron-chagall.dts
index c81d5875c31c..4012f9c799a8 100644
--- a/arch/arm/boot/dts/nvidia/tegra30-pegatron-chagall.dts
+++ b/arch/arm/boot/dts/nvidia/tegra30-pegatron-chagall.dts
@@ -2628,7 +2628,7 @@ cpu3: cpu@3 {
 	};
 
 	display-panel {
-		compatible = "panel-lvds";
+		compatible = "hannstar,hsd101pww2", "panel-lvds";
 
 		width-mm = <217>;
 		height-mm = <136>;
--- >8 ---

That gets rid of the DT validation warning for me. Would you be able to
test this on actual hardware? I think the compatible matching would
result in this matching the simple-panel driver and that does have some
support for LVDS, but I'm not sure if it's exactly equal to what you get
with only the panel-lvds matching, which makes this get handled by the
panel-lvds driver.

I'm attaching the full patch to make it a bit easier to apply this.

Thierry

From d45f49a40b0e9db07cb4fcdcaafd29e1453e8001 Mon Sep 17 00:00:00 2001
From: Thierry Reding <treding@xxxxxxxxxx>
Date: Mon, 17 Jul 2023 09:15:33 +0200
Subject: [PATCH] WIP: Use Hannstar HSD101PWW2 on Pegatron Chagall

Signed-off-by: Thierry Reding <treding@xxxxxxxxxx>
---
 .../bindings/display/panel/panel-lvds.yaml           |  2 ++
 .../bindings/display/panel/panel-simple.yaml         |  2 --
 .../arm/boot/dts/nvidia/tegra30-pegatron-chagall.dts |  2 +-
 drivers/gpu/drm/panel/panel-simple.c                 | 12 ++++++------
 4 files changed, 9 insertions(+), 9 deletions(-)

diff --git a/Documentation/devicetree/bindings/display/panel/panel-lvds.yaml b/Documentation/devicetree/bindings/display/panel/panel-lvds.yaml
index 929fe046d1e7..344e5df40c2f 100644
--- a/Documentation/devicetree/bindings/display/panel/panel-lvds.yaml
+++ b/Documentation/devicetree/bindings/display/panel/panel-lvds.yaml
@@ -40,6 +40,8 @@ properties:
     items:
       - enum:
           - auo,b101ew05
+          # HannStar Display Corp. HSD101PWW2 10.1" WXGA (1280x800) LVDS panel
+          - hannstar,hsd101pww2
           - tbs,a711-panel
 
       - const: panel-lvds
diff --git a/Documentation/devicetree/bindings/display/panel/panel-simple.yaml b/Documentation/devicetree/bindings/display/panel/panel-simple.yaml
index df1cec8fd21b..f4d9da4afefd 100644
--- a/Documentation/devicetree/bindings/display/panel/panel-simple.yaml
+++ b/Documentation/devicetree/bindings/display/panel/panel-simple.yaml
@@ -168,8 +168,6 @@ properties:
       - hannstar,hsd070pww1
         # HannStar Display Corp. HSD100PXN1 10.1" XGA LVDS panel
       - hannstar,hsd100pxn1
-        # HannStar Display Corp. HSD101PWW2 10.1" WXGA (1280x800) LVDS panel
-      - hannstar,hsd101pww2
         # Hitachi Ltd. Corporation 9" WVGA (800x480) TFT LCD panel
       - hit,tx23d38vm0caa
         # InfoVision Optoelectronics M133NWF4 R0 13.3" FHD (1920x1080) TFT LCD panel
diff --git a/arch/arm/boot/dts/nvidia/tegra30-pegatron-chagall.dts b/arch/arm/boot/dts/nvidia/tegra30-pegatron-chagall.dts
index c81d5875c31c..4012f9c799a8 100644
--- a/arch/arm/boot/dts/nvidia/tegra30-pegatron-chagall.dts
+++ b/arch/arm/boot/dts/nvidia/tegra30-pegatron-chagall.dts
@@ -2628,7 +2628,7 @@ cpu3: cpu@3 {
 	};
 
 	display-panel {
-		compatible = "panel-lvds";
+		compatible = "hannstar,hsd101pww2", "panel-lvds";
 
 		width-mm = <217>;
 		height-mm = <136>;
diff --git a/drivers/gpu/drm/panel/panel-simple.c b/drivers/gpu/drm/panel/panel-simple.c
index 18dc251749fb..b2fb7943f2ed 100644
--- a/drivers/gpu/drm/panel/panel-simple.c
+++ b/drivers/gpu/drm/panel/panel-simple.c
@@ -2108,13 +2108,13 @@ static const struct panel_desc hannstar_hsd100pxn1 = {
 static const struct display_timing hannstar_hsd101pww2_timing = {
 	.pixelclock = { 64300000, 71100000, 82000000 },
 	.hactive = { 1280, 1280, 1280 },
-	.hfront_porch = { 1, 1, 10 },
-	.hback_porch = { 1, 1, 10 },
-	.hsync_len = { 58, 158, 661 },
+	.hfront_porch = { 1, 1, 64 },
+	.hback_porch = { 1, 1, 64 },
+	.hsync_len = { 58, 158, 553 },
 	.vactive = { 800, 800, 800 },
-	.vfront_porch = { 1, 1, 10 },
-	.vback_porch = { 1, 1, 10 },
-	.vsync_len = { 1, 21, 203 },
+	.vfront_porch = { 1, 1, 32 },
+	.vback_porch = { 1, 1, 32 },
+	.vsync_len = { 1, 21, 159 },
 	.flags = DISPLAY_FLAGS_DE_HIGH,
 };
 
-- 
2.41.0

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