On 4/5/19 9:55 AM, Maxime Ripard wrote: > Hi, > > On Fri, Apr 05, 2019 at 06:24:55AM -0400, Yangtao Li wrote: >> Allwinner Process Voltage Scaling Tables defines the voltage and >> frequency value based on the speedbin blown in the efuse combination. >> The sunxi-cpufreq-nvmem driver reads the efuse value from the SoC to >> provide the OPP framework with required information. >> This is used to determine the voltage and frequency value for each >> OPP of operating-points-v2 table when it is parsed by the OPP framework. >> >> This change adds documentation for the DT bindings. >> The "operating-points-v2-sunxi-cpu" DT extends the "operating-points-v2" >> with following parameters: >> - nvmem-cells (NVMEM area containig the speedbin information) >> - opp-supported-hw: A single 32 bit bitmap value, >> representing compatible HW: >> 0: speedbin 0 >> 1: speedbin 1 >> 2: speedbin 2 >> 3-31: unused >> >> Signed-off-by: Yangtao Li <tiny.win...@gmail.com> >> --- >> .../bindings/opp/sunxi-nvmem-cpufreq.txt | 235 ++++++++++++++++++ >> 1 file changed, 235 insertions(+) >> create mode 100644 >> Documentation/devicetree/bindings/opp/sunxi-nvmem-cpufreq.txt >> >> diff --git a/Documentation/devicetree/bindings/opp/sunxi-nvmem-cpufreq.txt >> b/Documentation/devicetree/bindings/opp/sunxi-nvmem-cpufreq.txt >> new file mode 100644 >> index 000000000000..80201d4e5147 >> --- /dev/null >> +++ b/Documentation/devicetree/bindings/opp/sunxi-nvmem-cpufreq.txt >> @@ -0,0 +1,235 @@ >> +Allwinner Technologies, Inc. NVMEM CPUFreq and OPP bindings >> +=================================== >> + >> +For some SoCs, the CPU frequency subset and voltage value of each OPP >> +varies based on the silicon variant in use. Allwinner Process Voltage >> +Scaling Tables defines the voltage and frequency value based on the >> +speedbin blown in the efuse combination. The sunxi-cpufreq-nvmem driver >> +reads the efuse value from the SoC to provide the OPP framework with >> +required information. >> + >> +Required properties: >> +-------------------- >> +In 'cpus' nodes: >> +- operating-points-v2: Phandle to the operating-points-v2 table to use. >> + >> +In 'operating-points-v2' table: >> +- compatible: Should be >> + - 'operating-points-v2-sunxi-cpu'. >> +- nvmem-cells: A phandle pointing to a nvmem-cells node representing the >> + efuse registers that has information about the >> + speedbin that is used to select the right frequency/voltage >> + value pair. >> + Please refer the for nvmem-cells >> + bindings Documentation/devicetree/bindings/nvmem/nvmem.txt >> + and also examples below. >> + >> +In every OPP node: >> +- opp-supported-hw: A single 32 bit bitmap value, representing compatible >> HW. >> + Bitmap: >> + 0: speedbin 0 >> + 1: speedbin 1 >> + 2: speedbin 2 >> + 3-31: unused > > I'm wondering if that's the right approach. > > I guess we could also have three different OPP tables, and pass them > all three through a phandle array, and have the kernel code select > which one is relevant based on the SID content > > Another option would be to use the OF_DYNAMIC code to fill > operating-points-v2 at kernel boot, before (or when) cpufreq kicks in. > > ATF could also do that work.
While ATF has code to read and parse the DTB (which it uses to set up the PMIC), it's not really in a position to modify the DTB. For one thing, it only has access to the DTB appended to u-boot, not any DTB loaded from disk. And for two, that would add a significant amount of code, when ATF is already reaching its size limits. Cheers, Samuel
