[201811] Dell: Fix S6000 reboot issue (#6688)

#### Why I did it
Reboot command in Dell S6000 failed to reboot the switch.

#### How I did it
Added retry mechanism and CPU reset.

device/dell/x86_64-dell_s6000_s1220-r0/platform_reboot

@@ -1,13 +1,63 @@
-#!/bin/sh
+#!/usr/bin/env python
 
-# Export GPIO10 if needed
-[ -d /sys/class/gpio/gpio10 ] || echo 10 > /sys/class/gpio/export
-echo out > /sys/class/gpio/gpio10/direction
+import sys
+import os
+import struct
 
-#Toggle GPIO10 pin (to reset MUX)
-echo 1 > /sys/class/gpio/gpio10/value
-echo 0 > /sys/class/gpio/gpio10/value
+PORT_RES = '/dev/port'
+NVRAM_RES = '/dev/nvram'
+COLD_RESET = 0xE     # Cold Reset
+WARM_RESET = 0x6     # Warm Reset
+RESET_REG = 0xCF9
 
+def io_reg_write(resource, offset, val):
+    fd = os.open(resource, os.O_RDWR)
+    if fd < 0:
+        print('file open failed %s" % resource')
+        return
+    if os.lseek(fd, offset, os.SEEK_SET) != offset:
+        print('lseek failed on %s' % resource)
+        return
+    ret = os.write(fd, struct.pack('B', val))
+    if ret != 1:
+        print('write failed %d' % ret)
+        return
+    os.close(fd)
 
-#Power Reset
-echo 1 > /sys/devices/platform/dell-s6000-cpld.0/power_reset
+def power_reset(val):
+    with open('/sys/devices/platform/dell-s6000-cpld.0/power_reset', 'w') as p:
+        p.write(str(int(val)) + '\n')
+        p.flush()
+
+def gpio_direction(pin, direction):
+    kernpath = '/sys/class/gpio/gpio'+str(pin)+'/direction'
+    with open(('kernpath'), 'w') as p:
+        p.write(str(direction) + '\n')
+        p.flush()
+
+def gpio_set(pin, value):
+    kernpath = '/sys/class/gpio/gpio'+str(pin)+'/value'
+    with open(('kernpath'), 'w') as p:
+        p.write(str(int(value)) + '\n')
+        p.flush()
+
+def gpio_export(value):
+    with open('/sys/class/gpio/export', 'w') as p:
+        p.write(str(int(value)) + '\n')
+        p.flush()
+
+if __name__ == "__main__":
+
+    retry_count = 0
+    io_reg_write(NVRAM_RES, 0x49, COLD_RESET)
+
+    while retry_count < 3:
+        if not os.path.isdir("/sys/class/gpio/gpio10"):
+            gpio_export(10)
+        gpio_direction("10", "out")
+        # Toggle GPIO10 pin (to reset MUX)
+        gpio_set("10", 1)
+        gpio_set("10", 0)
+        power_reset(1)
+        retry_count += 1
+    io_reg_write(PORT_RES, RESET_REG, COLD_RESET)