On 22/12/22 21:16, Dmitry Osipenko wrote:
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20.12.2022 19:02, Sumit Gupta пишет:
Add support to use OPP table from DT in Tegra194 cpufreq driver.
Tegra SoC's receive the frequency lookup table (LUT) from BPMP-FW.
Cross check the OPP's present in DT against the LUT from BPMP-FW
and enable only those DT OPP's which are present in LUT also.
The OPP table in DT has CPU Frequency to bandwidth mapping where
the bandwidth value is per MC channel. DRAM bandwidth depends on the
number of MC channels which can vary as per the boot configuration.
This per channel bandwidth from OPP table will be later converted by
MC driver to final bandwidth value by multiplying with number of
channels before sending the request to BPMP-FW.
If OPP table is not present in DT, then use the LUT from BPMP-FW directy
as the frequency table and not do the DRAM frequency scaling which is
same as the current behavior.
Now, as the CPU Frequency table is being controlling through OPP table
in DT. Keeping fewer entries in the table will create less frequency
steps and scale fast to high frequencies if required.
It's not exactly clear what you're doing here. Are you going to scale
memory BW based on CPU freq? If yes, then this is wrong because CPU freq
is independent from the memory subsystem.
All Tegra30+ SoCs have ACTMON hardware unit that monitors CPU memory
activity and CPU memory BW should be scaled based on CPU memory events
counter. We have ACTMON devfreq driver for older SoCs. I have no clue
how ACTMON can be accessed on T186+, perhaps there should be a BPMP FW
API for that.
Yes, scaling the memory BW based on CPU freq.
Referred below patch set for previous generation of Tegra Soc's which
you mentioned and tried to trace the history.
https://patchwork.ozlabs.org/project/linux-tegra/patch/1418719298-25314-3-git-send-email-tomeu.vizoso@xxxxxxxxxxxxx/
In new Tegra Soc's, actmon counter control and usage has been moved to
BPMP-FW where only 'MCALL' counter is used and 'MCCPU is not being used.
Using the actmon counter was a reactive way to scale the frequency which
is less effective due to averaging over a time period.
We are now using the proactive way where clients tell their bandwidth
needs to help achieve better performance.
