On 6/16/22 00:22, Stephen Boyd wrote:
Quoting Marek Vasut (2022-06-15 14:55:17)
On 6/15/22 22:10, Stephen Boyd wrote:
Quoting Marek Vasut (2022-05-17 16:59:18)
diff --git a/Documentation/devicetree/bindings/clock/clock-bindings.txt b/Documentation/devicetree/bindings/clock/clock-bindings.txt
index f2ea53832ac63..d7f7afe2cbd0c 100644
--- a/Documentation/devicetree/bindings/clock/clock-bindings.txt
+++ b/Documentation/devicetree/bindings/clock/clock-bindings.txt
@@ -169,6 +169,22 @@ a shared clock is forbidden.
Configuration of common clocks, which affect multiple consumer devices can
be similarly specified in the clock provider node.
+==Critical clocks==
+
+Some platforms require some clocks to be always running, e.g. because those
+clock supply devices which are not otherwise attached to the system. One
+example is a system where the SoC serves as a crystal oscillator replacement
+for a programmable logic device. The critical-clocks property of a clock
+controller allows listing clock which must never be turned off.
+
+ clock-controller@a000f000 {
+ compatible = "vendor,clk95;
+ reg = <0xa000f000 0x1000>
+ #clocks-cells = <1>;
+ ...
+ critical-clocks = <UART3_CLK>, <SPI5_CLK>;
Historically "critical" is overloaded in the clk framework. We should
avoid using that name. What does "critical" even mean?
It means those clock must not be turned off, but there is no consumer
described in DT.
So it means "always on".
Instead I'd prefer "always-on-clocks" here, so we can indicate that
these clks should always be on. It would also parallel the property in
the regulator framework.
This property name is derived from protected-clock which you introduced.
I think it would be better to stay consistent within the clock framework
property names ?
protected-clocks is based on assigned-clocks. There isn't a
CLK_IS_PROTECTED flag. I'm not following your argument at all here,
sorry.
critical-clock property name is based on protected-clock property name.
There is also no CLK_IS_ALWAYS_ON flag , but there is CLK_IS_CRITICAL
flag . Sure, there is no CLK_IS_PROTECTED flag because the protected
clock is implemented only by a single driver (qualcomm).
I think it makes sense to align the DT property name and the flag name,
and the critical-clock is aligned with both other DT property names in
the clock framework and the flag name.
