On 17/10/2018 14:07, Dmitry Osipenko wrote: > On 10/17/18 3:59 PM, Jon Hunter wrote: >> >> On 17/10/2018 13:37, Dmitry Osipenko wrote: >>> On 10/17/18 11:40 AM, Jon Hunter wrote: >>>> >>>> On 30/08/2018 20:43, Dmitry Osipenko wrote: >>>>> Add device-tree binding that describes CPU frequency-scaling hardware >>>>> found on NVIDIA Tegra20/30 SoC's. >>>>> >>>>> Signed-off-by: Dmitry Osipenko <[email protected]> >>>>> --- >>>>> .../cpufreq/nvidia,tegra20-cpufreq.txt | 38 +++++++++++++++++++ >>>>> 1 file changed, 38 insertions(+) >>>>> create mode 100644 >>>>> Documentation/devicetree/bindings/cpufreq/nvidia,tegra20-cpufreq.txt >>>>> >>>>> diff --git >>>>> a/Documentation/devicetree/bindings/cpufreq/nvidia,tegra20-cpufreq.txt >>>>> b/Documentation/devicetree/bindings/cpufreq/nvidia,tegra20-cpufreq.txt >>>>> new file mode 100644 >>>>> index 000000000000..2c51f676e958 >>>>> --- /dev/null >>>>> +++ b/Documentation/devicetree/bindings/cpufreq/nvidia,tegra20-cpufreq.txt >>>>> @@ -0,0 +1,38 @@ >>>>> +Binding for NVIDIA Tegra20 CPUFreq >>>>> +================================== >>>>> + >>>>> +Required properties: >>>>> +- clocks: Must contain an entry for each entry in clock-names. >>>>> + See ../clocks/clock-bindings.txt for details. >>>>> +- clock-names: Must include the following entries: >>>>> + - pll_x: main-parent for CPU clock, must be the first entry >>>>> + - backup: intermediate-parent for CPU clock >>>>> + - cpu: the CPU clock >>>> >>>> Is it likely that 'backup' will be anything other that pll_p? If not why >>>> not just call it pll_p? Personally, I don't 'backup' to descriptive even >>>> though I can see what you mean. >>>> >>>> I can see that you want to make this flexible, but if the likelihood is >>>> that we will just use pll_p then I am not sure it is warranted at this >>>> point. >>> >>> That won't describe HW, but software. And device tree should describe HW. >> >> Hmm ... well that's my point exactly. So why call it 'backup'? Sounds >> like a software description to me. > > Because HW is designed the way that CPU parent need to be switched to the > backup clock source while main clock changes its rate. HW also allow to > select among different parents, pll_p is one of those parents.
Yes that part is understood. I am just splitting hairs over the actual name. We do the same for tegra124 but we just call it 'pll_p'. See ... Documentation/devicetree/bindings/cpufreq/nvidia,tegra124-cpufreq.txt Cheers Jon -- nvpublic
