Re: [PATCH v3 1/2] dt-bindings: clock: mediatek: Add SMI LARBs reset for MT8188

On Wed, Jan 22, 2025 at 07:40:12AM +0000, Friday Yang (杨阳) wrote:

On Tue, 2025-01-21 at 17:30 +0000, Conor Dooley wrote:

quoted

On Tue, Jan 21, 2025 at 02:50:40PM +0800, Friday Yang wrote:

quoted

SMI LARBs require reset functions when applying clamp operations.
Add '#reset-cells' for the clock controller located in image,
camera
and IPE subsystems.

A new required property is an abi break, please explain why this is
required.

You never answered this part. From a quick check, looks like the change
you made will cause probe failures if the resets are not present? Maybe
I misread the driver code in my quick skim - but that is the implication
of a new required property, so I didn't dig super far.

Adding new properties that break a driver is not really acceptable, so I
hope I made a mistake there.

What are "SMI LARBs"? Why did things previously work

quoted

without
acting as a reset controller?

The background can refer to the discussion in the following link:

https://lore.kernel.org/all/CAFGrd9qZhObQXvm2_abqaX83xMLqxjQETB2=wXpobDWU1CnvkA@mail.gmail.com/ (local)

https://lore.kernel.org/all/CAPDyKFpokXV2gJDgowbixTvOH_5VL3B5H8eyhP+KJ5Fasm2rFg@mail.gmail.com/ (local)
SMI clamp and reset operations should be implemented in SMI driver
instead of PM driver.

So the answer to how it worked previously was that nothing actually used
this multimedia interface?

Your commit message needs to explain why a new required property is okay
and why it was not there before.

Thanks,
Conor.

I previously added the SMI reset control driver. However, the
reviewer's comments are correct, these functions have already
been implemented in the clock control driver. There is no need
to submit duplicate code. 

https://lore.kernel.org/lkml/20241120063305.8135-2-friday.yang@mediatek.com/ (local)

https://lore.kernel.org/lkml/20241120063305.8135-3-friday.yang@mediatek.com/ (local)


On the MediaTek platform, the SMI block diagram like this:

                DRAM
                 |
            EMI(External Memory Interface)
                 |  |
          MediaTek IOMMU(Input Output Memory Management Unit)
                 |  |
             SMI-Common(Smart Multimedia Interface Common)
                 |
         +----------------+------------------+
         |                |                  |
         |                |                  |
         |                |                  |
         |                |                  |
         |                |                  |
       larb0       SMI-Sub-Common0     SMI-Sub-Common1
                   |      |     |      |             |
                  larb1  larb2 larb3  larb7       larb9

The SMI-Common connects with SMI LARBs and IOMMU. The maximum LARBs
number that connects with a SMI-Common is 8. If the engines number is
over 8, sometimes we use a SMI-Sub-Common which is nearly same with
SMI-Common. It supports up to 8 input and 1 output(SMI-Common has 2
output).

quoted

quoted

Signed-off-by: Friday Yang <redacted>
---
 .../bindings/clock/mediatek,mt8188-clock.yaml | 21
+++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git
a/Documentation/devicetree/bindings/clock/mediatek,mt8188-
clock.yaml
b/Documentation/devicetree/bindings/clock/mediatek,mt8188-
clock.yaml
index 860570320545..2985c8c717d7 100644

--- a/Documentation/devicetree/bindings/clock/mediatek,mt8188-

clock.yaml

+++ b/Documentation/devicetree/bindings/clock/mediatek,mt8188-

clock.yaml

@@ -57,6 +57,27 @@ required:
   - reg
   - '#clock-cells'

+allOf:
+  - if:
+      properties:
+        compatible:
+          contains:
+            enum:
+              - mediatek,mt8188-camsys-rawa
+              - mediatek,mt8188-camsys-rawb
+              - mediatek,mt8188-camsys-yuva
+              - mediatek,mt8188-camsys-yuvb
+              - mediatek,mt8188-imgsys-wpe1
+              - mediatek,mt8188-imgsys-wpe2
+              - mediatek,mt8188-imgsys-wpe3
+              - mediatek,mt8188-imgsys1-dip-nr
+              - mediatek,mt8188-imgsys1-dip-top
+              - mediatek,mt8188-ipesys
+
+    then:
+      required:
+        - '#reset-cells'
+
 additionalProperties: false

 examples:
--

2.46.0