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Subject[PATCH v7 0/5] mfd: tps6586x: register restart handler
Date
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.

---
v7:
- 5/5: drop mode check (suggested by Dmitry)
- Link to v6: https://lore.kernel.org/r/20230327-tegra-pmic-reboot-v6-0-af44a4cd82e9@skidata.com

v6:
- drop 4/6 to abort restart on unexpected failure (suggested by Dmitry)
- 4,5: fix comments in handlers (suggested by Lee)
- 4,5: same delay for both handlers (suggested by Lee)

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

---
Benjamin Bara (5):
kernel/reboot: emergency_restart: set correct system_state
i2c: core: run atomic i2c xfer when !preemptible
kernel/reboot: add device to sys_off_handler
mfd: tps6586x: use devm-based power off handler
mfd: tps6586x: register restart handler

drivers/i2c/i2c-core.h | 2 +-
drivers/mfd/tps6586x.c | 50 ++++++++++++++++++++++++++++++++++++++++++--------
include/linux/reboot.h | 3 +++
kernel/reboot.c | 4 ++++
4 files changed, 50 insertions(+), 9 deletions(-)
---
base-commit: 197b6b60ae7bc51dd0814953c562833143b292aa
change-id: 20230327-tegra-pmic-reboot-4175ff814a4b

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

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