Re: [PATCH v2 00/48] Introduce core voltage scaling for NVIDIA Tegra20/30 SoCs

On Thu, Dec 17, 2020 at 09:05:50PM +0300, Dmitry Osipenko wrote:

Introduce core voltage scaling for NVIDIA Tegra20/30 SoCs, which reduces
power consumption and heating of the Tegra chips. Tegra SoC has multiple
hardware units which belong to a core power domain of the SoC and share
the core voltage. The voltage must be selected in accordance to a minimum
requirement of every core hardware unit.

The minimum core voltage requirement depends on:

  1. Clock enable state of a hardware unit.
  2. Clock frequency.
  3. Unit's internal idling/active state.

This series is tested on Acer A500 (T20), AC100 (T20), Nexus 7 (T30),
Ouya (T30), TK1 (T124) and some others. I also added voltage scaling to
the Ventana (T20) and Cardhu (T30) boards which are tested by NVIDIA's CI
farm. Tegra30 is now couple degrees cooler on Nexus 7 and stays cool on
Ouya (instead of becoming burning hot) while system is idling. It should
be possible to improve this further by implementing a more advanced power
management features for the kernel drivers.

The DVFS support is opt-in for all boards, meaning that older DTBs will
continue to work like they did it before this series. It should be possible
to easily add the core voltage scaling support for Tegra114+ SoCs based on
this grounding work later on, if anyone will want to implement it.

The same comment as for your interconnect work: for sets touching
multiple systems please mention the dependencies between patches in the
cover letter. Not as a reply to such remark like I make here, but as a
separate entry in the cover letter.

Best regards,
Krzysztof