[PATCH v5 0/6] mfd: tps6586x: register restart handler

[Benjamin Bara]

Hi!

The Tegra20 requires an enabled VDE power domain during startup. As the
VDE is currently not used, it is disabled during runtime.
Since 8f0c714ad9be, there is a workaround for the "normal restart path"
which enables the VDE before doing PMC's warm reboot. This workaround is
not executed in the "emergency restart path", leading to a hang-up
during start.

This series implements and registers a new pmic-based restart handler
for boards with tps6586x. This cold reboot ensures that the VDE power
domain is enabled during startup on tegra20-based boards.

Since bae1d3a05a8b, i2c transfers are non-atomic while preemption is
disabled (which is e.g. done during panic()). This could lead to
warnings ("Voluntary context switch within RCU") in i2c-based restart
handlers during emergency restart. The state of preemption should be
detected by i2c_in_atomic_xfer_mode() to use atomic i2c xfer when
required. Beside the new system_state check, the check is the same as
the one pre v5.2.

v4: https://lore.kernel.org/r/20230327-tegra-pmic-reboot-v4-0-b24af219fb47@xxxxxxxxxxx
v3: https://lore.kernel.org/r/20230327-tegra-pmic-reboot-v3-0-3c0ee3567e14@xxxxxxxxxxx
v2: https://lore.kernel.org/all/20230320220345.1463687-1-bbara93@xxxxxxxxx/
system_state: https://lore.kernel.org/all/20230320213230.1459532-1-bbara93@xxxxxxxxx/
v1: https://lore.kernel.org/all/20230316164703.1157813-1-bbara93@xxxxxxxxx/

v5:
- introduce new 3 & 4, therefore 3 -> 5, 4 -> 6
- 3: provide dev to sys_off handler, if it is known
- 4: return NOTIFY_DONE from sys_off_notify, to avoid skipping
- 5: drop Reviewed-by from Dmitry, add poweroff timeout
- 5,6: return notifier value instead of direct errno from handler
- 5,6: use new dev field instead of passing dev as cb_data
- 5,6: increase timeout values based on error observations
- 6: skip unsupported reboot modes in restart handler

v4:
- 1,2: add "Fixes" and adapt commit messages
- 4: reduce delay after requesting the restart (as suggested by Dmitry)

v3:
- bring system_state back in this series
- do atomic i2c xfer if not preemptible (as suggested by Dmitry)
- fix style issues mentioned by Dmitry
- add cc stable as suggested by Dmitry
- add explanation why this is needed for Jon

v2:
- use devm-based restart handler
- convert the existing power_off handler to a devm-based handler
- handle system_state in extra series

---
Benjamin Bara (6):
      kernel/reboot: emergency_restart: set correct system_state
      i2c: core: run atomic i2c xfer when !preemptible
      kernel/reboot: add device to sys_off_handler
      kernel/reboot: sys_off_notify: always return NOTIFY_DONE
      mfd: tps6586x: use devm-based power off handler
      mfd: tps6586x: register restart handler

 drivers/i2c/i2c-core.h |  2 +-
 drivers/mfd/tps6586x.c | 55 ++++++++++++++++++++++++++++++++++++++++++--------
 include/linux/reboot.h |  3 +++
 kernel/reboot.c        | 11 +++++++++-
 4 files changed, 61 insertions(+), 10 deletions(-)
---
base-commit: 197b6b60ae7bc51dd0814953c562833143b292aa
change-id: 20230327-tegra-pmic-reboot-4175ff814a4b

Best regards,
-- 
Benjamin Bara <benjamin.bara@xxxxxxxxxxx>