From: Mark Brown <[email protected]> The ARMv7 topology code uses the ePAPR specified mandatory clock-frequency property to determine the relative performances of the CPUs along with the CPU type. However with FDT we don't update to take account of the current speed and if the cores are not running at full speed on boot then a device tree which is accurate on boot can provide incorrect information about the relative performances of the cores.
Document the current usage both to override ePAPR and to make the binding within the kernel more complete. Ideally the kernel would use information from the CPU frequency scaling drivers here but they may in turn consider this property and such changes are likely to be part of the energy aware scheduling work so not immediately available. Signed-off-by: Mark Brown <[email protected]> --- Documentation/devicetree/bindings/arm/cpus.txt | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/Documentation/devicetree/bindings/arm/cpus.txt b/Documentation/devicetree/bindings/arm/cpus.txt index 91304353eea4..e3726f6bca92 100644 --- a/Documentation/devicetree/bindings/arm/cpus.txt +++ b/Documentation/devicetree/bindings/arm/cpus.txt @@ -191,6 +191,15 @@ nodes to be present and contain the properties described below. property identifying a 64-bit zero-initialised memory location. + - clock-frequency + Usage: required + Value type: <u32> or <u64> + Definition: + This is specified in ePAPR as the current clock + frequency of the CPU. When used with these + extensions it should reflect the maximum clock + frequency for the CPU. + Example 1 (dual-cluster big.LITTLE system 32-bit): cpus { -- 1.8.5.1 -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
