net: fec: Reload PTP registers after link-state change

On link-state change, the controller gets reset,
which clears all PTP registers, including PHC time,
calibrated clock correction values etc. For correct
IEEE 1588 operation we need to restore these after
the reset.

Fixes: 6605b730 ("FEC: Add time stamping code and a PTP hardware clock")
Signed-off-by: Csókás, Bence <csokas.bence@prolan.hu>
Reviewed-by: Wei Fang <wei.fang@nxp.com>
Link: https://patch.msgid.link/20240924093705.2897329-2-csokas.bence@prolan.huSigned-off-by: Paolo Abeni <pabeni@redhat.com>

drivers/net/ethernet/freescale/fec.h

@@ -693,6 +693,9 @@ struct fec_enet_private {
 
 	struct {
 		int pps_enable;
+		u64 ns_sys, ns_phc;
+		u32 at_corr;
+		u8 at_inc_corr;
 	} ptp_saved_state;
 
 	u64 ethtool_stats[];

drivers/net/ethernet/freescale/fec_ptp.c

@@ -767,24 +767,44 @@ void fec_ptp_init(struct platform_device *pdev, int irq_idx)
 void fec_ptp_save_state(struct fec_enet_private *fep)
 {
 	unsigned long flags;
+	u32 atime_inc_corr;
 
 	spin_lock_irqsave(&fep->tmreg_lock, flags);
 
 	fep->ptp_saved_state.pps_enable = fep->pps_enable;
 
+	fep->ptp_saved_state.ns_phc = timecounter_read(&fep->tc);
+	fep->ptp_saved_state.ns_sys = ktime_get_ns();
+
+	fep->ptp_saved_state.at_corr = readl(fep->hwp + FEC_ATIME_CORR);
+	atime_inc_corr = readl(fep->hwp + FEC_ATIME_INC) & FEC_T_INC_CORR_MASK;
+	fep->ptp_saved_state.at_inc_corr = (u8)(atime_inc_corr >> FEC_T_INC_CORR_OFFSET);
+
 	spin_unlock_irqrestore(&fep->tmreg_lock, flags);
 }
 
 /* Restore PTP functionality after a reset */
 void fec_ptp_restore_state(struct fec_enet_private *fep)
 {
+	u32 atime_inc = readl(fep->hwp + FEC_ATIME_INC) & FEC_T_INC_MASK;
 	unsigned long flags;
+	u32 counter;
+	u64 ns;
 
 	spin_lock_irqsave(&fep->tmreg_lock, flags);
 
 	/* Reset turned it off, so adjust our status flag */
 	fep->pps_enable = 0;
 
+	writel(fep->ptp_saved_state.at_corr, fep->hwp + FEC_ATIME_CORR);
+	atime_inc |= ((u32)fep->ptp_saved_state.at_inc_corr) << FEC_T_INC_CORR_OFFSET;
+	writel(atime_inc, fep->hwp + FEC_ATIME_INC);
+
+	ns = ktime_get_ns() - fep->ptp_saved_state.ns_sys + fep->ptp_saved_state.ns_phc;
+	counter = ns & fep->cc.mask;
+	writel(counter, fep->hwp + FEC_ATIME);
+	timecounter_init(&fep->tc, &fep->cc, ns);
+
 	spin_unlock_irqrestore(&fep->tmreg_lock, flags);
 
 	/* Restart PPS if needed */