[PATCH V7 0/4] firmware: ti_sci: Introduce system suspend support

[Dhruva Gole]

Abstract
********

This series introduces necessary ti_sci driver functionality to support
DeepSleep mode (suspend to mem) on TI K3 AM62x. DeepSleep mode is
described in section "6.2.4.4 DeepSleep" of the AM62x Technical Reference
Manual [0].

Summary
*******

This series is a fixup and rebase of the patch series by
Dave Gerlach [1]. It applies on top of next-20230731.

The kernel triggers entry to DeepSleep 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
  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
  details. The supported firmware version is from TI Processor SDK
  >= 09.00 ie. tag 09.00.00.006 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.

* The firmware requires that the OS sends a TISCI_MSG_PREPARE_SLEEP
  message in order to provide details about suspend, so we must add the
  ability to send this message. We also add TISCI_MSG_LPM_WAKE_REASON
  and TISCI_MSG_SET_IO_ISOLATION messages as part of a new PM ops. These
  messages are part of the TISCI PM Low Power Mode API [2]. (Patch 2)

* A memory address must be provided to the firmware using the above
  message, which is allocated and managed by dma_alloc_attrs()
  and friends. This memory address can be used by the firmware to
  save necessary context at that physical location in the DDR RAM. (Patch 3)

* Finally, the ti_sci driver must actually send TISCI_MSG_PREPARE_SLEEP
  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. (Patch 4)

It currently enables only DeepSleep mode, but even if any additional
modes are needed to be supported in future, they would not require any
changes to the TISCI LPM APIs [2]. The enabling of additional modes
would be done via GenPD changes that is currently in the works.

Testing:
*******

In can be tested with the following branch:
https://github.com/DhruvaG2000/v-linux/commits/lpm-upstream-6.5

Tested on SK-AM62B [6] here:
https://gist.github.com/DhruvaG2000/8410fac048c677c40cd94f5169b5b0b4

Limitations:
************

* It is critical for deepsleep to work that the bootloader has
loaded the TIFS stub at the desired location and that the DM has copied
it correctly into it's TCM. Linux has no way of knowing whether a valid
FS Stub exists and has been loaded or not. The Device Manager also
doesn't send any NACK if a proper TIFS Stub is not present to prevent
the deepsleep somehow. This problem is somewhat addressed in this patch
series where we check which SOCs support LPM and based on that set the
fw_caps.

* Currently, DeepSleep is only supported on SK-AM62B with DDR4.
Boards with LPDDR part like Beagle Play and AM62x LP have a known FW issue.

Base commit:
************

commit ec8939156379 (tag: next-20230731) ("Add linux-next specific files for 20230731")

origin:
linux-next      https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git

Changelog:
**********

v7:
- Address Andrew's concerns on SYSFW fw_caps API
- Remove all the unused functions and variables including
  set_io_isolation and wake_reason calls
- use dma_free_attrs
- remove IO isolation related code from linux side,
TODO: Add it in ATF enter_sleep perhaps?

v6:
- link to v6 [5]
- Loading of FS Stub from linux no longer needed, hence drop that patch,
- Drop 1/6 and 5/6 from the previous series [4].
- Add system suspend resume callbacks which were removed in
commit 9225bcdedf16297a346082e7d23b0e8434aa98ed ("firmware: ti_sci: Use
system_state to determine polling")
- Use IO isolation while putting the system in suspend to RAM

v5:
- Add support (patch 3) for detecting the low power modes (LPM) of the
  FW/SoC with a recently introduced core TISCI_MSG_QUERY_FW_CAPS message.
- Use TISCI_MSG_QUERY_FW_CAPS instead of misusing the TISCI_MSG_PREPARE_SLEEP
  to detect the FW/SoC low power caps (patch 4).
- Take into account the supported LPMs in ti_sci_prepare_system_suspend()
  and handle the case when CONFIG_SUSPEND is not enabled (patch 6) that
  was reported by Roger Quadros and LKP.
- Pick up Rob Herring's "Reviewed-by" tag for the binding patch.

v4:
- Fix checkpacth warnings in patches 2 and 3.
- Drop the links with anchors in patch 2.

v3:
- Fix the compile warnings on 32-bit platforms reported by the kernel
  test robot in patches (3,5).
- Pick up Roger's "Tested-by" tags.

v2:
- Addressed comments received for v1 series [1].
- Updated v1 patch 5 to use pm notifier to avoid firmware loading
  issues.
- Dropped the reserved region requirement and allocate DMA memory
  instead. The reserved region binding patch is also removed.
- Introduce two more TISCI LPM messages that are supported in SysFW.
- Fixes in error handling.

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

[0] https://www.ti.com/lit/pdf/spruiv7
[1] https://lore.kernel.org/lkml/20220421203659.27853-1-d-gerlach@xxxxxx
[2] https://software-dl.ti.com/tisci/esd/latest/2_tisci_msgs/pm/lpm.html
[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=ti-linux-firmware-next&id=905eb58564581d951d148f45828e8c8a142a5938
[5] https://lore.kernel.org/all/20230803064247.503036-1-d-gole@xxxxxx/
[6] https://www.ti.com/tool/SK-AM62B


Cc: Andrew Davis <afd@xxxxxx>
Cc: Vibhore Vardhan <vibhore@xxxxxx>
Cc: Kevin Hilman <khilman@xxxxxxxxxxxx>
Cc: Vignesh Raghavendra <vigneshr@xxxxxx>
Cc: Tony Lindgren <tony@xxxxxxxxxxx>

Dave Gerlach (2):
  firmware: ti_sci: Introduce Power Management Ops
  firmware: ti_sci: Allocate memory for Low Power Modes

Dhruva Gole (1):
  firmware: ti_sci: Add system suspend call

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

 drivers/firmware/ti_sci.c              | 234 ++++++++++++++++++++++++-
 drivers/firmware/ti_sci.h              |  56 +++++-
 include/linux/soc/ti/ti_sci_protocol.h |  15 ++
 3 files changed, 303 insertions(+), 2 deletions(-)

-- 
2.34.1