@@ -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 clock 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>;
+ };
+
==Protected clocks==
Some platforms or firmwares may not fully expose all the clocks to the OS, such
Some platforms require select clock to be always running, e.g. because those clock supply vital devices which are not otherwise attached to the system and thus do not have a matching DT node and clock consumer. An 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 listed in the "critical-clocks" property may have other consumers in DT, listing the clock in "critical-clocks" only assures those clock are never turned off, and none of these optional additional consumers can turn the clock off either. The implementation is modeled after "protected-clocks". Signed-off-by: Marek Vasut <marex@denx.de> Cc: Michael Turquette <mturquette@baylibre.com> Cc: Rob Herring <robh+dt@kernel.org> Cc: Stephen Boyd <sboyd@kernel.org> Cc: devicetree@vger.kernel.org To: linux-clk@vger.kernel.org --- V2: Update the commit message to clarify the behavior --- .../devicetree/bindings/clock/clock-bindings.txt | 16 ++++++++++++++++ 1 file changed, 16 insertions(+)