Date

22 Oct 2020

Attendees

Summary

How to handle interrupt and more generally speaking asynchronous event in SCMI server in OP-TEE ?
- OP-TEE interrupt handling and OP-TEE thread context can't interact directly: interrupt can't start or wake up a thread context. Thread contexts are only executed based on a non secure world invocation
- The proposal is to let linux to handle the HW interrupt and send a proprietary scmi message using OEM/ODM range
  - message content from linux to SCP firmware will be as simple as the irq number. A module in SCP firmware will then put an event for the targeted module (like i2c, sensor) to handle the event
- Studied and started to work on this on fvp. Wanted to use sensor scmi notification for the PoC
  - SCMI sensor notification in SCP firmware should be available in few weeks
- Letting Linux to handle interrupt and forward the asynchronous event to SCMI server is acceptable only for none critical event that can't impact the integrity of the system (unlike reaching max Tj ). In the latter case OP-TEE must catch the critical event and act accordingly (like resetting or powering down the system). So we could have to share the interrupt between secure and non secure. OP-TEE will check if the interrupt is raised because of a critical event and linux will take care of non critical events
  - forwarding the HW interrupt from optee to non secure might not be possible
  - using one SPI for secure world to trigger non secure interrupt
- Ruchika : add an action to look if SWG can do something about enabling interaction between interrupt and thread context
new scmi patchset on linux
- 1st patchset about clean up and supporting OEM protocol
  - vincent to review them next week
- 2nd patchset voltage regulator
  - etienne reviewed and tested it
Round table
- Souvik : About SCMI specification v3
  - End Of October: comment acceptance closed
  - Release of scmi v3 targeted for end of november
- Etienne : how to move forward on merging SCP code into OP-TEE ?
  - we need to define an Execution Environment Interface which is architecture independent on which OP-TEE interface can be attached. And also other execution environnement
  - Is optee compatible with some posix interface ? No
  - Need to look at other "OS" like
    - zephyr or TFA SEL0 to define a generic i/f
    - running in a secure partition. Sidenote: 1st step will be to use optee to handle SEL0 before moving on hafnium
- Starting comparison about which interfaces from different Execution environment
  - Optee: Etienne
  - zephyr: Souvik
  - SEL0 TFA: Ruchika to point some documents. Interface should be same as FFA

Action items

Etienne Carriere (Deactivated) study OP-TEE interface for an SCP layer
Souvik Chakravarty check what it would mean for zephyr
Ruchika Gupta (Deactivated) : point some document for SEL0 TFA