On 08/07/2013 08:46 AM, Viresh Kumar wrote:
cpufreq-cpu0 driver needs OPPs to be present in DT which can be probed by it to get frequency table. This patch adds OPPs and clock-latency to tegra cpu0 node for multiple SoCs.
Voltage levels aren't used until now for tegra and so a flat value which would eventually be ignored is used to represent voltage.
This patch is problematic w.r.t. DT being an ABI.
We can certainly add new optional properties to a DT binding that enable new features. However, a new version of a binding can't require new properties to exist that didn't before, since that means that old DTs won't work with new kernels that require the new properties.
As such, I believe we do need some Tegra-specific piece of code that defines these OPP tables in the kernel, so that the operating-points property is not needed.
Similarly, we can't put invalid voltages into the DT, since if a later kernel version starts actually using that field, the HW will no longer work correctly. Unless perhaps we put 0 into the DT and make the binding define that 0 means "you can't change the voltage at all away from the boot value"?
Is the operating-points property documented in Documentation/devicetree/bindings/ somewhere?
(Also Cc'ing the DT mailing list and maintainers)
diff --git a/arch/arm/boot/dts/tegra114.dtsi b/arch/arm/boot/dts/tegra114.dtsi index abf6c40..730e0d9 100644 --- a/arch/arm/boot/dts/tegra114.dtsi +++ b/arch/arm/boot/dts/tegra114.dtsi @@ -438,6 +438,18 @@ device_type = "cpu"; compatible = "arm,cortex-a15"; reg = <0>;
operating-points = </* kHz ignored */216000 1000000312000 1000000456000 1000000608000 1000000760000 1000000816000 1000000912000 10000001000000 1000000>;clock-latency = <300000>;