Very few available memory frequencies

There are very few emc memory frequencies available on the nano, compared to the TK1, TX1, TX2, and so on:

$ cat /sys/kernel/debug/clk/emc_master/clk_possible_rates 
204000 1600000 (kHz)
$

Is there a kernel config option (e.g. DTS) or otherwise plans to expose some of the mid-region emc frequencies as well?

Hi krisrstkzp2o, we don’t currently have plans to enable additional memory frequencies on the Nano. Will keep you posted if that changes.

Hi Dusty!

Thank you for your quick reply.

I’ve written my PhD on the topic of the (now obsolete) Tegra K1 and power usage, and followed closely the development of the X1, X2 and Xavier, which are all more and more targeted towards high performance computing. (If interested, here is my talk from GTC2015: https://on-demand-gtc.gputechconf.com/gtcnew/on-demand-gtc.php?searchByKeyword=stokke&searchItems=&sessionTopic=&sessionEvent=&sessionYear=&sessionFormat=&submit=&select=)

The Nano is such a promising step toward the more constrained environment where energy is an issue, and I am really excited to see how it will hold up. Therefore, it seems a bit counter-intuitive to me to remove support for fine-grained LPDDR4 frequency scaling, which has been present in every single predecessor (at least from the K1’s era). For both the A57 CPU cluster and the GPU there are a lot of available frequency operating points…

Keeping in mind that there is about 1300 mW difference between the maximum and lowest memory frequency at 1.6 GHz and 204 MHz, respectively, I think this is a feature that really should be there…