Re: [PATCH 2/3] dt-bindings: usb: mtk-xhci: Allow middle optional clocks to be missing

On 20/06/2022 08:59, Chunfeng Yun wrote:

On Sun, 2022-06-19 at 14:05 +0200, Krzysztof Kozlowski wrote:

quoted

On 19/06/2022 09:46, Chunfeng Yun wrote:

quoted

On Fri, 2022-06-17 at 18:25 -0700, Krzysztof Kozlowski wrote:

quoted

On 17/06/2022 15:29, Nícolas F. R. A. Prado wrote:

quoted

The current clock list in the binding doesn't allow for one of
the
optional clocks to be missing and a subsequent clock to be
present.
An
example where this is an issue is in mt8192.dtsi, which has
"sys_ck",
"ref_ck", "xhci_ck" and would cause dtbs_check warnings.

Change the clock list in a way that allows the middle optional
clocks to
be missing, while still guaranteeing a fixed order. The
"ref_ck" is
kept
as a const even though it is optional for simplicity, since it
is
present in all current dts files.

Signed-off-by: Nícolas F. R. A. Prado <redacted>
---

 .../devicetree/bindings/usb/mediatek,mtk-xhci.yaml       | 9
+++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git
a/Documentation/devicetree/bindings/usb/mediatek,mtk-
xhci.yaml b/Documentation/devicetree/bindings/usb/mediatek,mtk-
xhci.yaml
index 63cbc2b62d18..99a1b233ec90 100644

--- a/Documentation/devicetree/bindings/usb/mediatek,mtk-

xhci.yaml

+++ b/Documentation/devicetree/bindings/usb/mediatek,mtk-

xhci.yaml

@@ -80,8 +80,13 @@ properties:
     items:
       - const: sys_ck  # required, the following ones are

optional
       - const: ref_ck
-      - const: mcu_ck
-      - const: dma_ck
+      - enum:
+          - mcu_ck
+          - dma_ck
+          - xhci_ck
+      - enum:
+          - dma_ck
+          - xhci_ck
       - const: xhci_ck

You allow now almost any order here, including incorrect like
sys,ref,xhci,xhci,xhci.

The order of clocks has to be fixed and we cannot allow
flexibility.
Are
you sure that these clocks are actually optional (not wired to
the
device)?

In fact, these optional clocks are fixed, due to no gates are
provided,
SW can't control them by CCF;
In this case, I usually use a fixed clock, or ignore it.

But in some versions these clocks are controllable or not?

Some SoCs are controllable, some ones are not (fixed clock).

Thanks for confirming. Then I would prefer to make these clocks required
(not optional) and always provide them - via common clock framework or
fixed-clock.

Best regards,
Krzysztof

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