[DellEMC] S6100 - iTCO watchdog support and reboot cause determination changes (#9149)

Why I did it
To support iTCO watchdog using watchdog APIs.
How I did it
Implemented a new watchdog class WatchdogTCO for interfacing with iTCO watchdog.
Updated reboot cause determination logic.
How to verify it
Verified that the watchdog APIs' return values are as expected.
Logs: UT_logs.txt

device/dell/x86_64-dell_s6100_c2538-r0/installer.conf

@@ -1,3 +1,3 @@
 CONSOLE_PORT=0x2f8
 CONSOLE_DEV=1
-ONIE_PLATFORM_EXTRA_CMDLINE_LINUX="module_blacklist=gpio_ich nos-config-part=/dev/sda12"
+ONIE_PLATFORM_EXTRA_CMDLINE_LINUX="module_blacklist=gpio_ich,wdat_wdt acpi_no_watchdog=1 nos-config-part=/dev/sda12"

platform/broadcom/sonic-platform-modules-dell/s6100/scripts/track_reboot_reason.sh

@@ -15,6 +15,7 @@ MAILBOX_POWERON_REASON=/sys/devices/platform/SMF.512/hwmon/*/mb_poweron_reason
 NVRAM_DEVICE_FILE=/dev/nvram
 RESET_REASON_FILE=/host/reboot-cause/platform/reset_reason
 SMF_DIR=/sys/devices/platform/SMF.512/hwmon/
+TCO_RESET_NVRAM_OFFSET=0x59
 
 while [[ ! -d $SMF_DIR ]]
 do
@@ -27,6 +28,7 @@ do
 done
 
 SMF_RESET=$(cat $SMF_RESET_REASON)
+TCO_WD_RESET=0
 
 if [[ -d /host/reboot-cause/platform ]]; then
     reboot_dir_found=true
@@ -80,6 +82,18 @@ _get_smf_reset_register(){
             echo "Fourth reset - $fourth_reset" >> $RESET_REASON_FILE
         fi
         logger -p user.info -t DELL_S6100_REBOOT_CAUSE "RST value in NVRAM: $first_reset, $second_reset, $third_reset, $fourth_reset"
+
+        if [[ $BIOS_VERSION_MINOR -gt 8 ]]; then
+            # Retrieve TCO reset status
+            tco_nvram=$((16#$(nvram_rd_wr.py --get --offset $TCO_RESET_NVRAM_OFFSET | cut -d " " -f 2)))
+            TCO_WD_RESET=$(($tco_nvram & 1))
+            logger -p user.info -t DELL_S6100_REBOOT_CAUSE "TCO status value in NVRAM: $TCO_WD_RESET"
+
+            # Clear TCO reset status in NVRAM
+            tco_nvram=$(printf "%x" $(($tco_nvram & 0xfe)))
+            nvram_rd_wr.py --set --val $tco_nvram --offset $TCO_RESET_NVRAM_OFFSET
+        fi
+
         # Clearing NVRAM values to holding next reset values
         nvram_rd_wr.py --set --val 0xee --offset 0x58
         nvram_rd_wr.py --set --val 0xee --offset 0x5c
@@ -183,7 +197,9 @@ update_mailbox_register(){
            && [[ $SMF_MSS_VERSION_MAJOR -ge 2 ]] && [[ $SMF_MSS_VERSION_MINOR -ge 7 ]] \
            && [[ $SMF_FPGA_VERSION_MAJOR -ge 1 ]] && [[ $SMF_FPGA_VERSION_MINOR -ge 4 ]]; then
 
-            if [[ $reason = "cc" ]]; then
+            if [[ $TCO_WD_RESET = 1 ]]; then
+                echo 0xdd > $MAILBOX_POWERON_REASON
+            elif [[ $reason = "cc" ]]; then
                 _is_software_reboot
             elif [[ $SMF_RESET = "11" ]]; then
                 echo 0xee > $MAILBOX_POWERON_REASON
@@ -206,6 +222,8 @@ update_mailbox_register(){
                 echo 0xee > $MAILBOX_POWERON_REASON
             elif [[ $is_wd_reboot = 1 ]] && [[ $reason != "cc" ]]; then
                 echo 0xdd > $MAILBOX_POWERON_REASON
+            elif [[ $TCO_WD_RESET = 1 ]]; then
+                echo 0xdd > $MAILBOX_POWERON_REASON
             elif [[ $reason = "cc" ]]; then
                 _is_software_reboot
             else

platform/broadcom/sonic-platform-modules-dell/s6100/sonic_platform/chassis.py

@@ -17,7 +17,7 @@ try:
     from sonic_platform.module import Module
     from sonic_platform.thermal import Thermal
     from sonic_platform.component import Component
-    from sonic_platform.watchdog import Watchdog
+    from sonic_platform.watchdog import Watchdog, WatchdogTCO
     from sonic_platform.eeprom import Eeprom
     import time
 except ImportError as e:
@@ -93,7 +93,13 @@ class Chassis(ChassisBase):
             component = Component(i)
             self._component_list.append(component)
 
-        self._watchdog = Watchdog()
+        bios_ver = self.get_component(0).get_firmware_version()
+        bios_minor_ver = bios_ver.split("-")[-1]
+        if bios_minor_ver.isdigit() and (int(bios_minor_ver) >= 9):
+            self._watchdog = WatchdogTCO()
+        else:
+            self._watchdog = Watchdog()
+
         self._transceiver_presence = self._get_transceiver_presence()
 
     def _get_reboot_reason_smf_register(self):

platform/broadcom/sonic-platform-modules-dell/s6100/sonic_platform/watchdog.py

@@ -1,5 +1,3 @@
-#!/usr/bin/env python
-
 ########################################################################
 #
 # DELLEMC S6100
@@ -10,13 +8,30 @@
 ########################################################################
 
 try:
+    import array
+    import ctypes
+    import fcntl
+    import glob
     import os
     import struct
-    import ctypes
     from sonic_platform_base.watchdog_base import WatchdogBase
 except ImportError as e:
     raise ImportError(str(e) + "- required module not found")
 
+# ioctl constants
+IOC_WRITE = 0x40000000
+IOC_READ = 0x80000000
+IOC_SIZE_INT = 0x00040000
+
+WATCHDOG_IOCTL_BASE = ord('W')
+
+WDIOC_SETOPTIONS = IOC_READ | IOC_SIZE_INT | (WATCHDOG_IOCTL_BASE << 8) | 4
+WDIOC_KEEPALIVE = IOC_READ | IOC_SIZE_INT | (WATCHDOG_IOCTL_BASE << 8) | 5
+WDIOC_SETTIMEOUT = IOC_READ | IOC_WRITE | IOC_SIZE_INT | (WATCHDOG_IOCTL_BASE << 8) | 6
+
+WDIOS_DISABLECARD = 0x0001
+WDIOS_ENABLECARD = 0x0002
+
 
 class _timespec(ctypes.Structure):
     _fields_ = [
@@ -24,6 +39,7 @@ class _timespec(ctypes.Structure):
             ('tv_nsec', ctypes.c_long)
     ]
 
+
 class Watchdog(WatchdogBase):
     """
     Abstract base class for interfacing with a hardware watchdog module
@@ -226,3 +242,142 @@ class Watchdog(WatchdogBase):
 
         return 0
 
+
+class WatchdogTCO(WatchdogBase):
+    """
+    Watchdog class for interfacing with iTCO watchdog
+    """
+
+    IDENTITY = "iTCO_wdt"
+
+    def __init__(self):
+
+        self.dev = None
+        self.dev_name = None
+        wd_sysfs_path = "/sys/class/watchdog"
+
+        for dev_file in glob.glob("/dev/watchdog*"):
+            dev = os.path.basename(dev_file)
+            dev_identity = self._read_file("{}/{}/identity".format(wd_sysfs_path, dev))
+            if dev_identity == self.IDENTITY:
+                self.dev_name = dev
+                break
+
+        if self.dev_name is None:
+            raise RuntimeError("{} is not initialized".format(self.IDENTITY))
+
+        self.state_file = "{}/{}/state".format(wd_sysfs_path, self.dev_name)
+        self.timeout_file = "{}/{}/timeout".format(wd_sysfs_path, self.dev_name)
+        self.timeleft_file = "{}/{}/timeleft".format(wd_sysfs_path, self.dev_name)
+
+    def __del__(self):
+        if self.dev is not None:
+            os.close(self.dev)
+
+    def _ioctl(self, request, arg=0, mutate_flag=True):
+        """
+        Perform ioctl on watchdog device
+        """
+        self._open_wd_dev()
+        fcntl.ioctl(self.dev, request, arg, mutate_flag)
+
+    def _open_wd_dev(self):
+        """
+        Open watchdog device file
+        """
+        if self.dev is None:
+            wd_dev = "/dev/{}".format(self.dev_name)
+            self.dev = os.open(wd_dev, os.O_RDWR)
+
+    @staticmethod
+    def _read_file(file_path):
+        """
+        Read a file
+        """
+        try:
+            with open(file_path, "r") as fd:
+                read_str = fd.read()
+        except OSError:
+            return -1
+
+        return read_str.strip()
+
+    def arm(self, seconds):
+        """
+        Arm the hardware watchdog with a timeout of <seconds> seconds.
+        If the watchdog is currently armed, calling this function will
+        simply reset the timer to the provided value. If the underlying
+        hardware does not support the value provided in <seconds>, this
+        method should arm the watchdog with the *next greater*
+        available value.
+
+        Returns:
+            An integer specifying the *actual* number of seconds the
+            watchdog was armed with. On failure returns -1.
+        """
+        if seconds < 0 or seconds > 0x3ff:
+            return -1
+        if seconds < 4:
+            seconds = 4
+
+        try:
+            timeout = int(self._read_file(self.timeout_file))
+            if timeout != seconds:
+                buf = array.array('I', [seconds])
+                self._ioctl(WDIOC_SETTIMEOUT, buf)
+                timeout = int(buf[0])
+
+            if self.is_armed():
+                self._ioctl(WDIOC_KEEPALIVE)
+            else:
+                buf = array.array('h', [WDIOS_ENABLECARD])
+                self._ioctl(WDIOC_SETOPTIONS, buf, False)
+        except OSError:
+            return -1
+        else:
+            return timeout
+
+    def disarm(self):
+        """
+        Disarm the hardware watchdog
+
+        Returns:
+            A boolean, True if watchdog is disarmed successfully, False
+            if not
+        """
+        disarmed = True
+        if self.is_armed():
+            try:
+                buf = array.array('h', [WDIOS_DISABLECARD])
+                self._ioctl(WDIOC_SETOPTIONS, buf, False)
+            except OSError:
+                disarmed = False
+
+        return disarmed
+
+    def is_armed(self):
+        """
+        Retrieves the armed state of the hardware watchdog.
+
+        Returns:
+            A boolean, True if watchdog is armed, False if not
+        """
+        state = self._read_file(self.state_file)
+        return state == "active"
+
+    def get_remaining_time(self):
+        """
+        If the watchdog is armed, retrieve the number of seconds
+        remaining on the watchdog timer
+
+        Returns:
+            An integer specifying the number of seconds remaining on
+            their watchdog timer. If the watchdog is not armed, returns
+            -1.
+
+        """
+        timeleft = -1
+        if self.is_armed():
+            timeleft = int(self._read_file(self.timeleft_file))
+
+        return timeleft