On 11/17/18 12:15 AM, Rob Herring wrote:

On Fri, Nov 16, 2018 at 01:54:45PM +0100, matthias.bgg@kernel.org wrote:

quoted

From: Matthias Brugger <mbrugger@suse.com>

On SoCs with no publical available HW or no working graphic stack
we change the devicetree binding for the mmsys clock part. This
way we don't need to register a platform device explicitly in the
drm driver. Instead we can create a mmsys child which invokes the
clock driver.

Signed-off-by: Matthias Brugger <mbrugger@suse.com>
---
 .../bindings/arm/mediatek/mediatek,mmsys.txt  | 21 ++++++++++++-------
 .../display/mediatek/mediatek,disp.txt        |  4 ++++
 2 files changed, 18 insertions(+), 7 deletions(-)

diff --git a/Documentation/devicetree/bindings/arm/mediatek/mediatek,mmsys.txt b/Documentation/devicetree/bindings/arm/mediatek/mediatek,mmsys.txt
index 4468345f8b1a..d4e205981363 100644
--- a/Documentation/devicetree/bindings/arm/mediatek/mediatek,mmsys.txt
+++ b/Documentation/devicetree/bindings/arm/mediatek/mediatek,mmsys.txt

@@ -1,4 +1,4 @@
-Mediatek mmsys controller
+Mediatek mmsys clock controller
 ============================
 
 The Mediatek mmsys controller provides various clocks to the system.

@@ -6,18 +6,25 @@ The Mediatek mmsys controller provides various clocks to the system.
 Required Properties:
 
 - compatible: Should be one of:
-	- "mediatek,mt2712-mmsys", "syscon"
-	- "mediatek,mt6797-mmsys", "syscon"
+	- "mediatek,mt2712-mmsys-clk", "syscon"
+	- "mediatek,mt6797-mmsys-clk", "syscon"

Doesn't match the example.>

quoted

 - #clock-cells: Must be 1
 
-The mmsys controller uses the common clk binding from
+The mmsys clock controller uses the common clk binding from
 Documentation/devicetree/bindings/clock/clock-bindings.txt
 The available clocks are defined in dt-bindings/clock/mt*-clk.h.
+It is a child of the mmsys block, see binding at:
+Documentation/devicetree/bindings/display/mediatek/mediatek,disp.txt
 
 Example:
 
-mmsys: clock-controller@14000000 {
-	compatible = "mediatek,mt8173-mmsys", "syscon";
+mmsys: syscon@14000000 {
+	compatible = "mediatek,mt2712-mmsys", "syscon", "simple-mfd";
 	reg = <0 0x14000000 0 0x1000>;
-	#clock-cells = <1>;
+
+	mmsys_clk: clock-controller@14000000 {
+		compatible = "mediatek,mt2712-mmsys-clk";
+		#clock-cells = <1>;

This goes against the general direction of not defining separate nodes 
for providers with no resources.

Why do you need this and what does it buy if you have to continue to 
support the existing chips?

It would show explicitly that the mmsys block is used to probe two
drivers, one for the gpu and one for the clocks. Otherwise that is
hidden in the drm driver code. I think it is cleaner to describe that in
the device tree.