net: fec: don't save PTP state if PTP is unsupported

Some platforms (such as i.MX25 and i.MX27) do not support PTP, so on
these platforms fec_ptp_init() is not called and the related members
in fep are not initialized. However, fec_ptp_save_state() is called
unconditionally, which causes the kernel to panic. Therefore, add a
condition so that fec_ptp_save_state() is not called if PTP is not
supported.

Fixes: a1477dc ("net: fec: Restart PPS after link state change")
Reported-by: Guenter Roeck <[email protected]>
Closes: https://lore.kernel.org/lkml/[email protected]/
Signed-off-by: Wei Fang <[email protected]>
Reviewed-by: Csókás, Bence <[email protected]>
Reviewed-by: Simon Horman <[email protected]>
Tested-by: Guenter Roeck <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

Author: Wei Fang

drivers/net/ethernet/freescale/fec_main.c

@@ -1077,7 +1077,8 @@ fec_restart(struct net_device *ndev)
 	u32 rcntl = OPT_FRAME_SIZE | 0x04;
 	u32 ecntl = FEC_ECR_ETHEREN;
 
-	fec_ptp_save_state(fep);
+	if (fep->bufdesc_ex)
+		fec_ptp_save_state(fep);
 
 	/* Whack a reset.  We should wait for this.
 	 * For i.MX6SX SOC, enet use AXI bus, we use disable MAC
@@ -1340,7 +1341,8 @@ fec_stop(struct net_device *ndev)
 			netdev_err(ndev, "Graceful transmit stop did not complete!\n");
 	}
 
-	fec_ptp_save_state(fep);
+	if (fep->bufdesc_ex)
+		fec_ptp_save_state(fep);
 
 	/* Whack a reset.  We should wait for this.
 	 * For i.MX6SX SOC, enet use AXI bus, we use disable MAC