[PATCH v3 0/4] Add support to read the restart reason from IMEM

[Kathiravan Thirumoorthy <kathiravan.thirumoorthy@oss.qualcomm.com>]

In Qualcomm IPQ SoC, if the system is rebooted due to the watchdog
timeout, there is no way to identify it. Current approach of checking
the EXPIRED_STATUS in WDT_STS is not working.

To achieve this, if the system is rebooted due to watchdog timeout, the
information is captured in the IMEM by the bootloader (along with other
reason codes as well).

This series attempts to address this by adding the support to read the
IMEM and populate the information via bootstatus sysfs file. As of now,
we are handling only the non secure watchdog timeout reason.

With the CONFIG_WATCHDOG_SYSFS enabled, user can extract the information
as below:

cat /sys/devices/platform/soc@0/f410000.watchdog/watchdog/watchdog0/bootstatus
32

Signed-off-by: Kathiravan Thirumoorthy <kathiravan.thirumoorthy@oss.qualcomm.com>
---
Changes in v3:
- Picked up the relevant tags
- Dropped the fallback compatible handling
- Split the driver changes into 2. Introduce the device data in one and
  extend the same in another for the use case
- Linke to v2:
  https://lore.kernel.org/linux-arm-msm/20250416-wdt_reset_reason-v2-0-c65bba312914@oss.qualcomm.com/

Changes in v2:
- Dropped the RFC tag
- Reworked the driver changes to use the syscon API
- Link to v1:
  https://lore.kernel.org/linux-arm-msm/20250408-wdt_reset_reason-v1-0-e6ec30c2c926@oss.qualcomm.com/

---
Kathiravan Thirumoorthy (4):
      dt-bindings: sram: qcom,imem: Document IPQ5424 compatible
      arm64: dts: qcom: ipq5424: Add the IMEM node
      watchdog: qcom: introduce the device data for IPQ5424 watchdog device
      watchdog: qcom: add support to read the restart reason from IMEM

 .../devicetree/bindings/sram/qcom,imem.yaml        |  1 +
 arch/arm64/boot/dts/qcom/ipq5424.dtsi              |  9 +++++
 drivers/watchdog/qcom-wdt.c                        | 47 +++++++++++++++++++++-
 3 files changed, 55 insertions(+), 2 deletions(-)
---
base-commit: 3e039dcc9c1320c0d33ddd51c372dcc91d3ea3c7
change-id: 20250408-wdt_reset_reason-e12921963fa6

Best regards,
-- 
Kathiravan Thirumoorthy <kathiravan.thirumoorthy@oss.qualcomm.com>