On Aug 09, 2024 at 15:53:43 +0200, Markus Schneider-Pargmann wrote:

Abstract
********

This series introduces necessary ti_sci driver functionality to support
various Suspend-to-RAM modes on TI AM62 family of devices. These Low
Power Modes include Deep Sleep and MCU Only as described in section
"6.2.4 Power Modes" of the AM62x Technical Reference Manual [0].

Since this code is common across AM62x, AM62A, AM62P, I think a more
suitable TRM link to give would be the AM62P TRM:

https://www.ti.com/lit/pdf/SPRUJ83

Reason: It covers more modes than the AM62x

Summary
*******

This series is a restructuring and rebase of the patch series by
Dave Gerlach [1] and Dhruva Gole [2]. It applies on top of Linux
6.11-rc1.

The kernel triggers entry to Low Power Mode through the mem suspend
transition with the following:

* At the bootloader stage, one is expected to package the TIFS stub
  which then gets pulled into the Tightly coupled memory of the Device Mgr
  (DM) R5 when it starts up. If using U-Boot, then it requires tispl.bin
  to contain the TIFS stub. Refer to ti-u-boot patch [3] for further

Everything is now in upstream U-Boot, hence I prefer to share upstream
ie. non-vendor tree links at this point.

Documentation: https://source.denx.de/u-boot/u-boot/-/commit/962f60abca82bb11501bc0c627abacda15bed076
Sample TIFS Stub packaging patch:
https://source.denx.de/u-boot/u-boot/-/commit/93458ba599f753dcc5b6fea661cf71a50e8c5bd2

Patches that introduced the base support:
https://source.denx.de/u-boot/u-boot/-/commit/4a0067c8575c7c3b98f3fc0a689f53dc80700393
https://source.denx.de/u-boot/u-boot/-/commit/128f81290b7d4f20a11c7754798b1896575b7a29

  details. The supported firmware version is from TI Processor SDK
  >= 10.00 ie. tag 10.00.04 from ti-linux-firmware [4].

* Use a TF-A binary that supports PSCI_SYSTEM_SUSPEND call. This causes
  system to use PSCI system suspend as last step of mem sleep.

* We add support for the TISCI_MSG_QUERY_FW_CAPS message, used to retrieve
  the firmware capabilities of the currently running system firmware [6].
  Sysfw version >= 10.00.04 support LPM_DM_MANAGED capability, where
  Device Mgr firmware now manages which low power mode is chosen. Going
  forward, this is the default configuration supported for TI AM62 family
  of devices. The state chosen by the DM can be influenced by sending
  constraints using the new LPM constraint APIs. (Patch 1)

* The firmware requires that the OS sends a TISCI_MSG_PREPARE_SLEEP
  message in order to provide details about suspend. The ti_sci driver
  must send this message to firmware with the above information
  included, which it does during the driver suspend handler when
  PM_MEM_SUSPEND is the determined state being entered. The mode being
  sent depends on whether firmware capabilities have support for
  LPM_DM_MANAGED feature. Legacy firmware or those supporting other
  modes can extend the mode selection logic as needed. (Patch 2)

* We also add the remaining TISCI Low Power Mode messages required for
  inquiring wake reason and managing LPM constraints as part of a new PM
  ops. These messages are part of the TISCI PM Low Power Mode API [5].
  (Patch 3)

* Finally if any CPUs have PM QoS resume latency constraints set, we
  aggregate these and set the TISCI system-wide latency constraint.
  (Patch 4)

Testing
*******

This series can for example be tested with a am62a-lp-sk board.

For am62a-lp-sk all usb nodes have to be disabled at the moment (usbss0,
usb0, usbss1 and usb1). There is currently an issue with USB Link Power
Management and turning off the USB device which is being worked on.

Once booted suspend/resume can be tested with rtcwake:
  $ rtcwake -m mem -s 10 -d /dev/rtc0

Make sure /dev/rtc0 corresponds to rtc-ti-k3:
  $ dmesg | grep rtc-ti-k3
  rtc-ti-k3 2b1f0000.rtc: registered as rtc0

[...]

Do we need to add an alias here for this?
https://kernel.googlesource.com/pub/scm/linux/kernel/git/torvalds/linux/+/refs/heads/master/arch/arm64/boot/dts/ti/k3-am62a7-sk.dts#19

References:
***********

[0] https://www.ti.com/lit/pdf/spruiv7
[1] https://lore.kernel.org/lkml/20220421203659.27853-1-d-gerlach@ti.com (local)
[2] https://lore.kernel.org/lkml/20230804115037.754994-1-d-gole@ti.com (local)
[3] https://git.ti.com/cgit/ti-u-boot/ti-u-boot/commit/?h=ti-u-boot-2023.04&id=91886b68025c7ad121e62d1fc1fa4601eeb736cd
[4] https://git.ti.com/cgit/processor-firmware/ti-linux-firmware/commit/?h=10.00.06&id=193f7d7570583a41ddc50a221e37c32be6be583e
[5] https://software-dl.ti.com/tisci/esd/latest/2_tisci_msgs/pm/lpm.html
[6] https://downloads.ti.com/tisci/esd/latest/2_tisci_msgs/general/core.html#tisci-msg-query-fw-caps

Dave Gerlach (1):
  firmware: ti_sci: Introduce Power Management Ops

Georgi Vlaev (1):
  firmware: ti_sci: Add support for querying the firmware caps

Kevin Hilman (1):
  firmware: ti_sci: add CPU latency constraint management

Vibhore Vardhan (1):
  firmware: ti_sci: Add system suspend and resume call

 drivers/firmware/ti_sci.c              | 452 ++++++++++++++++++++++++-
 drivers/firmware/ti_sci.h              | 137 +++++++-
 include/linux/soc/ti/ti_sci_protocol.h |  46 +++
 3 files changed, 633 insertions(+), 2 deletions(-)

-- 
Best regards,
Dhruva Gole [off-list ref]