[Arista7260cx3] Add platform specific reboot tool (#1318)

* [Arista7260cx3] Add platform specific reboot tool

* [utilities] update sonic-utilities submodule

device/arista/x86_64-arista_7260cx3_64/platform_reboot

@@ -0,0 +1,87 @@
+#!/usr/bin/env python
+# Copyright (c) 2018 Arista Networks, Inc.  All rights reserved.
+# Arista Networks, Inc. Confidential and Proprietary.
+
+# Reboot script for 7260CX3
+
+from __future__ import print_function
+import sys
+import mmap, os
+import subprocess
+from struct import pack, unpack
+
+class MmapResource( object ):
+   """Resource implementation for a directly-mapped memory region."""
+
+   def __init__( self, path ):
+      try:
+         fd = os.open( path, os.O_RDWR )
+      except EnvironmentError:
+         print( "FAIL can not open scd memory-map resource file" )
+         print( "FAIL are you running on the proper platform?" )
+         sys.exit( 1 )
+      try:
+         size = os.fstat( fd ).st_size
+      except EnvironmentError:
+         print( "FAIL can not fstat scd memory-map resource file" )
+         print( "FAIL are you running on the proper platform?" )
+         sys.exit( 1 )
+      try:
+         self.mmap_ = mmap.mmap( fd, size, mmap.MAP_SHARED,
+                      mmap.PROT_READ | mmap.PROT_WRITE )
+      except EnvironmentError:
+         print( "FAIL can not map scd memory-map file" )
+         print( "FAIL are you running on the proper platform?" )
+         sys.exit( 1 )
+      finally:
+         try:
+            # Note that closing the file descriptor has no effect on the memory map
+            os.close( fd )
+         except EnvironmentError:
+            print( "FAIL failed to close scd memory-map file" )
+            sys.exit( 1 )
+
+   def read32( self, addr ):
+      return unpack( '<L', self.mmap_[ addr : addr + 4 ] )[ 0 ]
+
+   def write32( self, addr, value ):
+      self.mmap_[ addr: addr + 4 ] = pack( '<L', value )
+
+def scdRegTest( scd, offset, val1, count ):
+   scd.write32( offset, val1 )
+   val2 = scd.read32( offset )
+   if val1 != val2:
+      print( "FAIL: scd write 0x%08x but read back 0x%08x in iter %d" %
+             ( val1, val2, count ) )
+      sys.exit( 17 )
+
+def scdScrRegTest( scd ):
+   scrOffset = 0x0130
+   for i in range( 0, 3 ):
+      scdRegTest( scd, scrOffset, 0xdeadbeef, i )
+      scdRegTest( scd, scrOffset, 0xa5a5a5a5, i )
+      scdRegTest( scd, scrOffset, 0x00000000, i )
+
+def reboot( scd ):
+   # reboot the system by writing to register 0x7000
+   print( "Rebooting" )
+   scd.write32( 0x7000, 0xDEAD )
+   print( "REBOOTED" )
+
+def main():
+   busName = "/sys/bus/pci/devices/0000:ff:0b.3/resource0"
+
+   subprocess.call( [ 'modprobe', 'scd' ] )
+
+   scd = MmapResource( busName )
+
+   #
+   # verify that we can read/write scd scratch register
+   #
+   scdScrRegTest( scd )
+
+   # reboot the system
+   reboot( scd )
+
+if __name__ == "__main__":
+   main()