Re: [PATCH v1 3/5] dt-bindings: arm: Add cpu-idle-states to Tegra194 CPU nodes

On Fri, Mar 12, 2021 at 02:27:30PM -0800, Sowjanya Komatineni wrote:

Hi Sudeep,

To make our driver PSCI compliant below are few updates to be done

1. Standardize passing residency time run-time thru PSCI to ATF.

Yes that was my initial understanding, but your previous response was
confusing. I should have read this first.

    From PSCI specification I only see PSCI_STAT_RESIDENCY and
PSCI_STAT_COUNT optional functions for PSCI1.0/PSCI1.1

Indeed, we don't have any support to pass run-time residency hints in PSCI
today.

   Can you please help add right people to explore on possible ways to add
PSCI function for passing corresponding state residency time to ATF?

Before we jump to implementation in TF-A we need to get agreement to get this
added to the specification to support in OSPM/Linux. TF-A is just one
implementation of PSCI and may not be only one.

Formally you can raise any specification related queries to
https://developer.arm.com/support or support@arm.com. I will ask the author
of PSCI specification internally to take a look at this thread and chime in
if they can.

2. Tegra CPU Idle support definitely need to pass deepest cluster state and
threshold to MCE firmware from DT and looks like we can move this
implementation to ATF

Yes, I just asked the same question as response to your earlier email. Thanks
for confirming that it can be moved out of OSPM/Linux and DT

     With both of the above implementation changes Tegra194 driver will be
PSCI compliant.

We still need to get agreement on the specification front 😉.

--
Regards,
Sudeep