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authorStephen Boyd <swboyd@chromium.org>2018-11-05 11:40:10 -0800
committerStephen Boyd <sboyd@kernel.org>2018-11-21 00:58:35 -0800
commit48d7f160b10711f014bf07b574c73452646c9fdd (patch)
tree5c6e72ee490057692bdea768b7a803e9861a2643 /Documentation
parent651022382c7f8da46cb4872a545ee1da6d097d2a (diff)
downloadlinux-48d7f160b10711f014bf07b574c73452646c9fdd.tar.bz2
dt-bindings: clk: Introduce 'protected-clocks' property
Add a generic clk property for clks which are not intended to be used by the OS due to security restrictions put in place by firmware. For example, on some Qualcomm firmwares reading or writing certain clk registers causes the entire system to reboot, but on other firmwares reading and writing those same registers is required to make devices like QSPI work. Rather than adding one-off properties each time a new set of clks appears to be protected, let's add a generic clk property to describe any set of clks that shouldn't be touched by the OS. This way we never need to register the clks or use them in certain firmware configurations. Cc: Rob Herring <robh+dt@kernel.org> Cc: Bjorn Andersson <bjorn.andersson@linaro.org> Cc: Taniya Das <tdas@codeaurora.org> Signed-off-by: Stephen Boyd <swboyd@chromium.org> Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org> Reviewed-by: Rob Herring <robh@kernel.org> Signed-off-by: Stephen Boyd <sboyd@kernel.org>
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/devicetree/bindings/clock/clock-bindings.txt16
1 files changed, 16 insertions, 0 deletions
diff --git a/Documentation/devicetree/bindings/clock/clock-bindings.txt b/Documentation/devicetree/bindings/clock/clock-bindings.txt
index 2ec489eebe72..b646bbcf7f92 100644
--- a/Documentation/devicetree/bindings/clock/clock-bindings.txt
+++ b/Documentation/devicetree/bindings/clock/clock-bindings.txt
@@ -168,3 +168,19 @@ a shared clock is forbidden.
Configuration of common clocks, which affect multiple consumer devices can
be similarly specified in the clock provider node.
+
+==Protected clocks==
+
+Some platforms or firmwares may not fully expose all the clocks to the OS, such
+as in situations where those clks are used by drivers running in ARM secure
+execution levels. Such a configuration can be specified in device tree with the
+protected-clocks property in the form of a clock specifier list. This property should
+only be specified in the node that is providing the clocks being protected:
+
+ clock-controller@a000f000 {
+ compatible = "vendor,clk95;
+ reg = <0xa000f000 0x1000>
+ #clocks-cells = <1>;
+ ...
+ protected-clocks = <UART3_CLK>, <SPI5_CLK>;
+ };