Ether channel interface suspended mode

Question

Connection between our core switch to access switch is showing suspended for etherchannel interface  
interface GigabitEthernet1/0/2
  switchport mode trunk
 channel-group 2 mode on
end
interface GigabitEthernet1/0/1
 switchport mode trunk
 channel-group 2 mode on
end
interface Port-channel2
 switchport mode trunk
GigabitEthernet1/0/1 is up, line protocol is down (suspended)
GigabitEthernet1/0/1 is up, line protocol is down (suspended)
MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation ARPA, loopback not set
Keepalive set (10 sec)
Full-duplex, 100Mb/s, media type is 10/100/1000BaseTX
input flow-control is off, output flow-control is unsupported
ARP type: ARPA, ARP Timeout 04:00:00
GigabitEthernet1/0/2 is up, line protocol is up (connected) 
  MTU 1500 bytes, BW 1000000 Kbit, DLY 10 usec, 
     reliability 255/255, txload 1/255, rxload 1/255
  Encapsulation ARPA, loopback not set
  Keepalive set (10 sec)
  Full-duplex, 1000Mb/s, media type is 10/100/1000Base
Logs:
TX%EC-5-CANNOT_BUNDLE2: Gi1/0/1 is not compatible with Gi1/0/2 and will be suspended (speed of Gi1/0/1 is 100M, Gi1/0/2 is 1000M)
why the speed is varying but i was configured as auto  , Kindly suggest 
Gi1/0/2    connected    trunk      a-full a-1000 10/100/1000BaseTX
Gi1/0/1    suspended    trunk      a-full  a-100 10/100/1000BaseTX

Answer 1

TX%EC-5-CANNOT_BUNDLE2: Gi1/0/1 is not compatible with Gi1/0/2 and will be suspended (speed of Gi1/0/1 is 100M, Gi1/0/2 is 1000M)
Gi1/0/2 connected trunk a-full a-1000 10/100/1000BaseTX
Gi1/0/1 suspended trunk a-full a-100 10/100/1000BaseTX
Make sense.  Look at the speed of both ports.  They are not the same.  And this is why Gi1/0/1 is suspended. 
Gi 1/0/1 could potentially have a faulty cable.  You could try running a TDR to determine.  
1.  Command:  test cable tdr interface Gi 1/0/1; 
2.  Wait for approximately 5 to 7 seconds; 
3.  Command:  sh cable tdr interface Gi 1/0/1; 
4.  Post the output to #3.