On Thursday, September 27, 2012 10:45 PM Sylwester Nawrocki wrote

Hi,

Cc: devicetree-discuss@lists.ozlabs.org

On 09/24/2012 09:36 PM, Ajay Kumar wrote:

quoted

This patch enables device tree based discovery support for DP driver.
The driver is modified to handle platform data in both the cases:
with DT and non-DT.
Documentation is also added for the DT bindings.

DP-PHY should be regarded as a seperate device node while
being passed from device tree list, and device node for
DP should contain DP-PHY as child node with property name "dp-phy"
associated with it.

Signed-off-by: Ajay Kumar<redacted>
---
  .../devicetree/bindings/video/exynos_dp.txt        |   83 ++++++++++
  drivers/video/exynos/exynos_dp_core.c              |  168 ++++++++++++++++++--
  drivers/video/exynos/exynos_dp_core.h              |    2 +
  3 files changed, 239 insertions(+), 14 deletions(-)
  create mode 100644 Documentation/devicetree/bindings/video/exynos_dp.txt

diff --git a/Documentation/devicetree/bindings/video/exynos_dp.txt

b/Documentation/devicetree/bindings/video/exynos_dp.txt

quoted

new file mode 100644
index 0000000..c27f892

--- /dev/null
+++ b/Documentation/devicetree/bindings/video/exynos_dp.txt

@@ -0,0 +1,83 @@
+Exynos Displayport driver should configure the displayport interface

Don't we need a whitespace between 'display' and 'port' ?

Either 'display port' or 'DisplayPort' is commonly used. 
For clarity, display port would be better.

quoted

+based on the type of panel connected to it.
+
+We use two nodes:
+	-dptx_phy node
+	-display-port-controller node
+
+For the dp-phy initialization, we use a dptx_phy node.
+Required properties for dptx_phy:
+	-compatible:
+		Should be "samsung,dp-phy".
+	-samsung,dptx_phy_reg:
+		Base address of DP PHY register.

Couldn't just 'reg' be used for this one ?

quoted

+	-samsung,enable_bit:
+		The bit used to enable/disable DP PHY.

Is this the bit mask or the bit index ? In the code it's used as
a bitmask. But from description it is not clear whether it is
an index or a mask. Is it different across various SoCs ?

Perhaps it's better to name it samsung,enable_mask (in case some
SoC need more than one bit) ?

It's the bit mask.
It is different across various SoCs.
OK, enable_mask would be better.

quoted

+
+For the Panel initialization, we read data from display-port-controller node.
+Required properties for display-port-controller:
+	-compatible:
+		Should be "samsung,exynos5-dp".
+	-reg:
+		physical base address of the controller and length
+		of memory mapped region.
+	-interrupts:
+		Internet combiner values.

what? :)

Ajay: Please, fix it.

quoted

+	-interrupt-parent:
+		Address of Interrupt combiner node.
+	-dp_phy:
+		Address of dptx_phy node.

"A phandle to dptx_phy node" ?

Yes, you're right.

Ajay: Please, replace 'Address of dptx_phy node'
       with 'phandle of dptx_phy node'.

quoted

+	-samsung,color_space:
+		input video data format.
+			COLOR_RGB = 0, COLOR_YCBCR422 = 1, COLOR_YCBCR444 = 2

Can this be changed at run time ?

No, it is not changeable.
It's a default setting according to eDP panel.

quoted

+	-samsung,dynamic_range:
+		dynamic range for input video data.
+			VESA = 0, CEA = 1

Why is it in the device tree ? Shouldn't it be configurable at runtime ?
My apologies if this an obvious question, I don't have much experience
with DP.

Same above.

quoted

+	-samsung,ycbcr_coeff:
+		YCbCr co-efficients for input video.
+			COLOR_YCBCR601 = 0, COLOR_YCBCR709 = 1
+	-samsung,color_depth:
+		Bit per color component.

"Number of bits per colour component" ? Also same remark as above.

Same above.

quoted

+			COLOR_6 = 0, COLOR_8 = 1, COLOR_10 = 2, COLOR_12 = 3
+	-samsung,link_rate:
+		link rates supportd by the panel.

typo: supportd -> supported

Ajay: Please fix it.

quoted

+			LINK_RATE_1_62GBPS = 0x6, LINK_RATE_2_70GBPS = 0x0A

Is this really a property of a panel ? Why it is in the PHY node ?
Also I can see this is just a single property, so "link rates" is a bit
misleading.

Yes, It's a property of LCD panel.
It is not in the 'PHY' node, but 'display-port-controller' node.

Ajay: Please replace 'link rates' with 'link rate'.

quoted

+	-samsung,lane_count:
+		number of lanes supported by the panel.
+			LANE_COUNT1 = 1, LANE_COUNT2 = 2, LANE_COUNT4 = 4

What do these symbolic names are needed for ? Is lane_count a number or a
mask, is this really a _maximum_ number of lanes ? What are the valid values,
1, 2 and 4 ? Or maybe 0x3 is also valid which  would indicate that we can
use 1 or 2 data lanes ?

These symbolic names are defined in './include/video/exynos_dp.h'.
It seems that Ajay used these definitions.

'lane_count' is a number of used lanes of main link which transfer data
streams as video. The number of lanes of Main Link is 1, 2, or 4 lanes.
It is dependent on eDP panel.

quoted

+	-samsung,interlaced:
+		Interlace scan mode.
+			Progressive if defined, Interlaced if not defined

Why do we need this in the device tree ? Is this really a default scan mode ?
Can it be the changed at runtime ?

No, it is not changeable.
It's a default setting according to eDP panel.

quoted

+	-samsung,v_sync_polarity:
+		VSYNC polarity configuration.
+			High if defined, Low if not defined
+	-samsung,h_sync_polarity:
+		HSYNC polarity configuration.
+			High if defined, Low if not defined
+
+Example:
+
+SOC specific portion:
+	dptx_phy: dptx_phy@0x10040720 {
+		compatible = "samsung,dp-phy";
+		samsung,dptx_phy_reg =<0x10040720>;
+		samsung,enable_bit =<1>;
+	};
+
+	display-port-controller {
+		compatible = "samsung,exynos5-dp";
+		reg =<0x145B0000 0x10000>;
+		interrupts =<10 3>;
+		interrupt-parent =<&combiner>;
+		dp_phy =<&dptx_phy>;

Shouldn't it be "samsung,dp_phy" ?

Do you mean this ? It is not working.
+		dp_phy = "samsung,dp_phy";

quoted

+        };
+
+Board Specific portion:
+	display-port-controller {
+		samsung,color_space =<0>;
+		samsung,dynamic_range =<0>;
+		samsung,ycbcr_coeff =<0>;
+		samsung,color_depth =<1>;
+		samsung,link_rate =<0x0a>;
+		samsung,lane_count =<2>;
+	};

--

Regards,
Sylwester