Some DWMAC variants such as dwmac1000 don't support discovering the
number of output pps and auxiliary snapshots. Allow these parameters to
be defined in default ptp_clock_info, and let them be updated only when
the feature discovery yielded a result.

Signed-off-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
---
 drivers/net/ethernet/stmicro/stmmac/stmmac_ptp.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_ptp.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_ptp.c
index 41581f516ea9..8ea2b4226234 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_ptp.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_ptp.c
@@ -303,8 +303,14 @@ void stmmac_ptp_register(struct stmmac_priv *priv)
 	if (priv->plat->has_gmac4 && priv->plat->clk_ptp_rate)
 		priv->plat->cdc_error_adj = (2 * NSEC_PER_SEC) / priv->plat->clk_ptp_rate;
 
-	priv->ptp_clock_ops.n_per_out = priv->dma_cap.pps_out_num;
-	priv->ptp_clock_ops.n_ext_ts = priv->dma_cap.aux_snapshot_n;
+	/* Update the ptp clock parameters based on feature discovery, when
+	 * available
+	 */
+	if (priv->dma_cap.pps_out_num)
+		priv->ptp_clock_ops.n_per_out = priv->dma_cap.pps_out_num;
+
+	if (priv->dma_cap.aux_snapshot_n)
+		priv->ptp_clock_ops.n_ext_ts = priv->dma_cap.aux_snapshot_n;
 
 	if (priv->plat->ptp_max_adj)
 		priv->ptp_clock_ops.max_adj = priv->plat->ptp_max_adj;
-- 
2.47.0