net: sfc: avoid using timespec

The sfc driver internally uses a time format based on 32-bit (unsigned)
seconds and 32-bit nanoseconds. This means it will overflow in 2106,
but the value we pass into it is a signed 32-bit tv_sec that already
overflows in 2038 to a negative value.

This patch changes the logic to use the lower 32 bits of the timespec64
tv_sec in efx_ptp_ns_to_s_ns, which will have the correct value beyond the overflow.
While this does not change any of the register values, it lets us
keep using the driver after we deprecate the use of the timespec type
in the kernel.

In the efx_ptp_process_times function, the change to use timespec64
is similar, in that the tv_sec portion is ignored anyway and we only
care about the nanosecond portion that remains unchanged.
Acked-by: Richard Cochran <richardcochran@gmail.com>
Acked-by: David S. Miller <davem@davemloft.net>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: John Stultz <john.stultz@linaro.org>

drivers/net/ethernet/sfc/ptp.c

@@ -401,8 +401,8 @@ size_t efx_ptp_update_stats(struct efx_nic *efx, u64 *stats)
 /* For Siena platforms NIC time is s and ns */
 static void efx_ptp_ns_to_s_ns(s64 ns, u32 *nic_major, u32 *nic_minor)
 {
-	struct timespec ts = ns_to_timespec(ns);
-	*nic_major = ts.tv_sec;
+	struct timespec64 ts = ns_to_timespec64(ns);
+	*nic_major = (u32)ts.tv_sec;
 	*nic_minor = ts.tv_nsec;
 }
 
@@ -431,8 +431,8 @@ static ktime_t efx_ptp_s_ns_to_ktime_correction(u32 nic_major, u32 nic_minor,
  */
 static void efx_ptp_ns_to_s27(s64 ns, u32 *nic_major, u32 *nic_minor)
 {
-	struct timespec ts = ns_to_timespec(ns);
-	u32 maj = ts.tv_sec;
+	struct timespec64 ts = ns_to_timespec64(ns);
+	u32 maj = (u32)ts.tv_sec;
 	u32 min = (u32)(((u64)ts.tv_nsec * NS_TO_S27_MULT +
 			 (1ULL << (NS_TO_S27_SHIFT - 1))) >> NS_TO_S27_SHIFT);
 
@@ -737,14 +737,14 @@ efx_ptp_process_times(struct efx_nic *efx, MCDI_DECLARE_STRUCT_PTR(synch_buf),
 	 */
 	for (i = 0; i < number_readings; i++) {
 		s32 window, corrected;
-		struct timespec wait;
+		struct timespec64 wait;
 
 		efx_ptp_read_timeset(
 			MCDI_ARRAY_STRUCT_PTR(synch_buf,
 					      PTP_OUT_SYNCHRONIZE_TIMESET, i),
 			&ptp->timeset[i]);
 
-		wait = ktime_to_timespec(
+		wait = ktime_to_timespec64(
 			ptp->nic_to_kernel_time(0, ptp->timeset[i].wait, 0));
 		window = ptp->timeset[i].window;
 		corrected = window - wait.tv_nsec;
@@ -803,7 +803,7 @@ efx_ptp_process_times(struct efx_nic *efx, MCDI_DECLARE_STRUCT_PTR(synch_buf),
 					  ptp->timeset[last_good].minor, 0);
 
 	/* Calculate delay from NIC top of second to last_time */
-	delta.tv_nsec += ktime_to_timespec(mc_time).tv_nsec;
+	delta.tv_nsec += ktime_to_timespec64(mc_time).tv_nsec;
 
 	/* Set PPS timestamp to match NIC top of second */
 	ptp->host_time_pps = *last_time;