[PATCH v6 2/9] dt-bindings: phy: rockchip,rk3588-mipi-dcphy: Select TX or RX, add phy-type

[Jason Yang]

The Samsung MIPI D-/C-PHY block on RK3588 and RK3576 has a transmitter
for DSI and a receiver for CSI-2, and the DSI host and the CSI-2 host
can use the transmitter and the receiver at the same time. The single
cell of this binding selects the mode and refers to the transmitter, so
the receiver cannot be described.

Change the cell to select the transmitter or the receiver. The
transmitter and the receiver cannot operate in different modes [1], so
the optional phy-type property of the PHY node sets the mode for the
whole block, D-PHY by default:

	/* the MIPI DSI host, driving the transmitter */
	phys = <&mipidcphy0 PHY_DIRECTION_TX>;

	/* the MIPI CSI-2 host, driving the receiver */
	phys = <&mipidcphy0 PHY_DIRECTION_RX>;

For C-PHY the consumers stay the same and the PHY node gets:

	phy-type = <PHY_TYPE_CPHY>;

Existing DTs on a newer kernel: PHY_TYPE_DPHY and PHY_TYPE_CPHY remain
valid as deprecated values. They select the transmitter and imply
phy-type = <PHY_TYPE_DPHY> or <PHY_TYPE_CPHY> respectively, so nothing
changes for them.

New DTs on an older kernel: an ABI break. The older kernel ignores
phy-type and takes any cell value as the mode of the block. A DSI node
with PHY_DIRECTION_TX therefore gets no display, and a CSI-2 node with
PHY_DIRECTION_RX gets no camera.

[1] RK3588 TRM: section 22.1 (overview): "The TX and RX only support
    operate in the same PHY mode."

Suggested-by: Michael Riesch <michael.riesch at collabora.com>
Link: https://lore.kernel.org/r/94d47cab-10c6-4ec3-84a0-3bddc9d67f5f@collabora.com
Signed-off-by: Jason Yang <jason98166 at gmail.com>
---
 .../bindings/phy/rockchip,rk3588-mipi-dcphy.yaml       | 18 +++++++++++++++---
 1 file changed, 15 insertions(+), 3 deletions(-)

diff --git a/Documentation/devicetree/bindings/phy/rockchip,rk3588-mipi-dcphy.yaml b/Documentation/devicetree/bindings/phy/rockchip,rk3588-mipi-dcphy.yaml
index c8ff5ba22a86..1ea21ab203ba 100644
--- a/Documentation/devicetree/bindings/phy/rockchip,rk3588-mipi-dcphy.yaml
+++ b/Documentation/devicetree/bindings/phy/rockchip,rk3588-mipi-dcphy.yaml
@@ -22,11 +22,23 @@ properties:
   "#phy-cells":
     const: 1
     description: |
-      Argument is mode to operate in. Supported modes are:
-        - PHY_TYPE_DPHY
-        - PHY_TYPE_CPHY
+      Argument defines whether receiver or transmitter PHY is used.
+        - PHY_DIRECTION_TX
+        - PHY_DIRECTION_RX
+
+      PHY_TYPE_DPHY and PHY_TYPE_CPHY are deprecated. They select the
+      transmitter and imply phy-type = <PHY_TYPE_DPHY> or <PHY_TYPE_CPHY>
+      respectively. Use PHY_DIRECTION_TX and phy-type instead.
+
       See include/dt-bindings/phy/phy.h for constants.
 
+  phy-type:
+    description: D-PHY (default) or C-PHY mode
+    enum:
+      - 10 # PHY_TYPE_DPHY
+      - 11 # PHY_TYPE_CPHY
+    default: 10
+
   clocks:
     maxItems: 2
 

-- 
2.43.0