chips: ibex: Enable low power state #1882
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ppannuto
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I have updated this addressing comments and rebasing it on #1886 |
This was referenced May 28, 2020
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I think this is blocked on #1886 for now. In the meantime, I'm still slightly worried about understanding how peripherals interact with the power manager. For example, on the SAM4L there is fairly complex logic that checks which sleep state is safe to enter based on the peripherals that are active. Does ibex manage the various sleep states automatically, or is this something that Tock will need to manage? |
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Signed-off-by: Alistair Francis <alistair.francis@wdc.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>
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I have updated this and it's no longer blocking. As for if the sleep state is safe to enter I don't see anything in the documentation describing that we need to check anything. |
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1887: sched: Add a watchdog r=bradjc a=alistair23 ### Pull Request Overview As part of #1882 we started talking about safe waits (#1552). I have a PR with some initial safe wait support (#1886) in that we can be interrupted while looping on a hardware condition. The idea here is that while entering low power mode we can skip the infinite loop if we get an interrupt. #1886 doesn't address a large number of loops in the driver capsules as they don't have access to `Chip` so it's more difficult to wait on interrupts. The harder part is what to do when a wait "fails". What happens when returning to full power fails to occur in a specific time, what happens when a bus fails to respond in a reasonable amount of time? How do we gracefully handle this and continue running in some capacity. This PR starts to implement a watchdog functionality. This is not instead of a safe wait (in lots of cases a safe wait would be more graceful) but is generally to help avoid infinite loops and help debugging. It is also something that has come up to help make Tock more reliable. It is up to `Chips` and boards to handle the watchdog interrupt and decided how to act. Currently we tickle the watch dog when iterating on each process and at the start of each kernel loop. ### Testing Strategy None ### TODO or Help Wanted Feedback ### Documentation Updated - [X] Updated the relevant files in `/docs`, or no updates are required. ### Formatting - [X] Ran `make format`. - [X] Fixed errors surfaced by `make clippy`. Co-authored-by: Alistair Francis <alistair.francis@wdc.com> Co-authored-by: Brad Campbell <bradjc5@gmail.com>
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Pull Request Overview
This PR configures the OpenTitan Power Management IP to enter low power mode before calling the WFI.
Testing Strategy
This pull request was tested by running Tock and apps on the FPGA OT instance.
TODO or Help Wanted
Documentation Updated
/docs, or no updates are required.Formatting
make format.make clippy.