[202012][Dell]S6100 - iTCO watchdog support and reboot cause determination changes (#16726)

To support iTCO watchdog in Dell S6100.
[Backport PR [DellEMC] S6100 - iTCO watchdog support and reboot cause determination changes #9149]

Microsoft ADO (25153914):

Update installer.conf for initializing the required drivers.
Update the reboot cause determination logic to check for iTCO watchdog reset if the BIOS version supports iTCO watchdog.

Author: ArunSaravananBalachandran

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 logs_inram=on"
+ONIE_PLATFORM_EXTRA_CMDLINE_LINUX="module_blacklist=gpio_ich,wdat_wdt acpi_no_watchdog=1 nos-config-part=/dev/sda12 logs_inram=on"

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 $TCO_RESET_NVRAM_OFFSET
+        fi
+
         # Clearing NVRAM values to holding next reset values
         nvram_rd_wr.py --set --val 0xee --offset 0x58
         nvram_rd_wr.py --set --val 0xee --offset 0x5c
@@ -131,7 +145,6 @@ _is_unknown_reset(){
         mb_poweron_reason=$(cat $MAILBOX_POWERON_REASON)
         echo "Unknown POR: $curr_poweron_reason RST: $curr_reset_reason MBR: $mb_poweron_reason" > $REBOOT_CAUSE_FILE
     fi
-    
 }
 
 update_mailbox_register(){
@@ -161,7 +174,9 @@ 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
                 echo 0xaa > $MAILBOX_POWERON_REASON
             elif [[ $SMF_RESET = "11" ]]; then
                 echo 0xee > $MAILBOX_POWERON_REASON
@@ -184,6 +199,8 @@ 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
                 echo 0xaa > $MAILBOX_POWERON_REASON
             else