[PATCH v2 0/3] watchdog: dw_wdt: fix reset line management

[Artem Shimko]

Hello,

This is v2 of the series fixing reset line management in the dw_wdt
driver. Compared to v1, the series is reduced from 5 patches to 3:
the manual reset_control_deassert()/reset_control_assert() handling
is replaced by the device-managed _deasserted variant from the start.

Patch 1 replaces devm_reset_control_get_optional_shared() with
devm_reset_control_get_optional_shared_deasserted(), so the reset line
is deasserted on acquisition, before the first register access in
dw_wdt_update_mode(), and is asserted again automatically by devres
when the device is removed. This removes the out_assert_rst label and
the explicit reset_control_assert() calls in probe error paths and in
dw_wdt_drv_remove(), and uses dev_err_probe() for the acquisition error.

Patch 2 adds reset line management during system suspend/resume:
the reset is asserted before clocks are disabled in suspend, and
deasserted after clocks are re-enabled and before the register state
is restored in resume. Error handling is added for the reset operations
in resume, with a cleanup path that disables the clocks in reverse
order of enabling.

Patch 3 cleans up the error paths in dw_wdt_resume().

Thank you.

Testing:

$ ls /dev/watchdog*
/dev/watchdog   /dev/watchdog1  /dev/watchdog3
/dev/watchdog0  /dev/watchdog2

$ ls /sys/class/watchdog/
watchdog0  watchdog1  watchdog2  watchdog3

$ chmod +x watchdog-test
$ ./watchdog-test -f /dev/watchdog0 -i -s
watchdog_info:
 identity:              Synopsys DesignWare Watchdog
 firmware_version:      0
Support/Status: Set timeout (in seconds)
Support/Status: Supports magic close char
Support/Status: Pretimeout (in seconds), get/set
Support/Status: Keep alive ping reply
Support/Status: Keep alive ping reply

$ echo mem > /sys/power/state
...
...
[ 1560.147058] PM: suspend exit
[ 1560.371470] usb 1-1: new high-speed USB device number 3 using xhci-hcd
[ 1561.031825] cdc_ncm 1-1:2.0: MAC-Address: a4:2a:95:e8:fc:e4
[ 1561.037736] cdc_ncm 1-1:2.0: setting rx_max = 16384
[ 1561.054408] cdc_ncm 1-1:2.0: setting tx_max = 16384
[ 1561.084713] cdc_ncm 1-1:2.0 eth0: register 'cdc_ncm' at usb-xhci-hcd.2.auto-1, CDC NCM (NO ZLP), a4:2a:95:e8:fc:e4

$ ./watchdog-test -f /dev/watchdog0 -i -s
watchdog_info:
 identity:              Synopsys DesignWare Watchdog
 firmware_version:      0
Support/Status: Set timeout (in seconds)
Support/Status: Supports magic close char
Support/Status: Pretimeout (in seconds), get/set
Support/Status: Keep alive ping reply
Support/Status: Keep alive ping reply

$ ls /dev/watchdog*
/dev/watchdog   /dev/watchdog1  /dev/watchdog3
/dev/watchdog0  /dev/watchdog2

$ echo 1 > /dev/watchdog0
$ cat /sys/kernel/debug/1e012000.wdt/registers | grep ccvr
ccvr = 0x09a7baab
$ cat /sys/kernel/debug/1e012000.wdt/registers | grep ccvr
ccvr = 0x0599dce0
$ cat /sys/kernel/debug/1e012000.wdt/registers | grep ccvr
ccvr = 0x01926467
$ [  110.392536] watchdog0: pretimeout event

--
Best regards,
Artem

ChangeLog:
  v1:
    * https://lore.kernel.org/all/20260320135624.223863-1-a.shimko.dev@xxxxxxxxx/T/#t
  v2:
    * Reduced from 5 patches to 3: manual reset handling is replaced by
      the devm _deasserted variant from the start, so the intermediate
      states that could leak the deasserted reset line are gone and every
      commit is self-contained.

Artem Shimko (3):
  watchdog: dw_wdt: use
    devm_reset_control_get_optional_shared_deasserted
  watchdog: dw_wdt: manage reset line during system suspend/resume
  watchdog: dw_wdt: clean up error paths in resume function

 drivers/watchdog/dw_wdt.c | 37 +++++++++++++++++++++----------------
 1 file changed, 21 insertions(+), 16 deletions(-)

-- 
2.43.0