On Tue, Sep 25, 2018 at 12:29 PM Dmitry Osipenko <digetx@xxxxxxxxx> wrote: > > On 9/25/18 7:58 PM, Rob Herring wrote: > > On Thu, Aug 30, 2018 at 10:43:52PM +0300, 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 <digetx@xxxxxxxxx> > >> --- > >> .../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 > > > > The Cortex A9 has CLK, PERIPHCLK, and PERIPHCLKEN clocks and only CLK > > is used for the cpu core. You can't just define your own clocks that > > you happen to want access to. > > > > Otherwise, you're not defining anything new here, so a binding document > > isn't required. > > PERIPHCLK is a different thing. Right, that's what I meant. Only CLK is used. > Here we are defining the CPU clock and > its *parent* sources, the PLLX (main) and backup (intermediate clock > that is used while PLLX changes its rate). These are not some random > clocks "that you happen to want access to", they are essential for the > Tegra CPUFreq driver, CPU is running off them. assigned-clocks is generally how we get parent clocks in this situation. "clocks" is for what physical clocks are attached to a given block. ARM very clearly documents the clocks for their IP blocks. > I assume that PERIPHCLK and other clocks are derived from the "CPU" > clock and their configuration is hardwired. Probably Peter knows how > it's implemented in HW. Yes, because PERIPHCLK must be synchronous. In any case, it is irrelevant to cpu nodes and applies to timer, SCU, and GIC nodes. > I'm now working on v2 that will include more Tegra-specific stuff in the > binding, like custom "opp-supported-hw" property and probably some more.
