[PATCH net v2] net: stmmac: propagate PTP addend and system time programming errors

[Lorenzo Bianconi]

stmmac_update_subsecond_increment() ignores the error returned by
stmmac_config_addend(), and stmmac_init_tstamp_counter() discards the
addend and system time programming errors, always returning success. A
failure to program the addend (PTP_TCR_TSADDREG) or to initialize the
system time counter (PTP_TCR_TSINIT) is therefore silently swallowed,
leaving the hardware timestamp counter in a non-running or partially
configured state while the driver keeps operating as if timestamping
were up. This matters for TAPRIO/EST offloading, which derives the gate
base time from the hardware timestamp counter.

Return error codes from stmmac_update_subsecond_increment(),
stmmac_init_tstamp_counter() and stmmac_dl_ts_coarse_set() instead of
silently returning success.

Fixes: cc4c9001ce31 ("net: stmmac: Switch stmmac_hwtimestamp to generic HW Interface Helpers")
Signed-off-by: Lorenzo Bianconi <lorenzo.bianconi@xxxxxxxxxxxxxxxx>
---
Changes in v2:
- Initialize sec_inc to 0 in stmmac_restore_subsecond_increment()
  routine.
- Link to v1: https://lore.kernel.org/r/20260920-stmmac-ptp-added-systime-error-v1-1-8ac9e7a3fce2@xxxxxxxxxxxxxxxx
---
 drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 87 ++++++++++++++++++-----
 1 file changed, 68 insertions(+), 19 deletions(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index 3f34d491c959..28a83f4a174b 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -601,31 +601,63 @@ static void stmmac_get_rx_hwtstamp(struct stmmac_priv *priv, struct dma_desc *p,
 	}
 }
 
-static void stmmac_update_subsecond_increment(struct stmmac_priv *priv)
+static void stmmac_restore_subsecond_increment(struct stmmac_priv *priv,
+					       u32 default_addend,
+					       u32 systime_flags)
 {
 	bool xmac = dwmac_is_xmac(priv->plat->core_type);
 	u32 sec_inc = 0;
+
+	stmmac_config_addend(priv, priv->ptpaddr, default_addend);
+	stmmac_config_hw_tstamping(priv, priv->ptpaddr, systime_flags);
+	stmmac_config_sub_second_increment(priv, priv->ptpaddr,
+					   priv->plat->clk_ptp_rate,
+					   xmac, &sec_inc);
+	priv->default_addend = default_addend;
+	priv->sub_second_inc = sec_inc;
+}
+
+static int stmmac_update_subsecond_increment(struct stmmac_priv *priv,
+					     u32 systime_flags)
+{
+	bool xmac = dwmac_is_xmac(priv->plat->core_type);
+	u32 sec_inc = 0, val;
 	u64 temp = 0;
+	int ret;
 
-	stmmac_config_hw_tstamping(priv, priv->ptpaddr, priv->systime_flags);
+	stmmac_config_hw_tstamping(priv, priv->ptpaddr, systime_flags);
 
 	/* program Sub Second Increment reg */
 	stmmac_config_sub_second_increment(priv, priv->ptpaddr,
 					   priv->plat->clk_ptp_rate,
 					   xmac, &sec_inc);
-	temp = div_u64(1000000000ULL, sec_inc);
-
-	/* Store sub second increment for later use */
-	priv->sub_second_inc = sec_inc;
+	if (!sec_inc) {
+		ret = -EINVAL;
+		goto error;
+	}
 
 	/* calculate default added value:
 	 * formula is :
 	 * addend = (2^32)/freq_div_ratio;
 	 * where, freq_div_ratio = 1e9ns/sec_inc
 	 */
+	temp = div_u64(1000000000ULL, sec_inc);
 	temp = (u64)(temp << 32);
-	priv->default_addend = div_u64(temp, priv->plat->clk_ptp_rate);
-	stmmac_config_addend(priv, priv->ptpaddr, priv->default_addend);
+	val = div_u64(temp, priv->plat->clk_ptp_rate);
+
+	ret = stmmac_config_addend(priv, priv->ptpaddr, val);
+	if (ret)
+		goto error;
+
+	priv->sub_second_inc = sec_inc;
+	priv->default_addend = val;
+
+	return 0;
+error:
+	/* Restore previous configuration */
+	stmmac_restore_subsecond_increment(priv, priv->default_addend,
+					   priv->systime_flags);
+	return ret;
 }
 
 /**
@@ -864,25 +896,37 @@ static int stmmac_hwtstamp_get(struct net_device *dev,
 static int stmmac_init_tstamp_counter(struct stmmac_priv *priv,
 				      u32 systime_flags)
 {
+	u32 default_addend = priv->default_addend;
 	struct timespec64 now;
+	int ret;
 
 	if (!priv->plat->clk_ptp_rate) {
 		netdev_err(priv->dev, "Invalid PTP clock rate");
 		return -EINVAL;
 	}
 
-	stmmac_config_hw_tstamping(priv, priv->ptpaddr, systime_flags);
-	priv->systime_flags = systime_flags;
-
-	stmmac_update_subsecond_increment(priv);
+	ret = stmmac_update_subsecond_increment(priv, systime_flags);
+	if (ret)
+		return ret;
 
 	/* initialize system time */
 	ktime_get_real_ts64(&now);
 
 	/* lower 32 bits of tv_sec are safe until y2106 */
-	stmmac_init_systime(priv, priv->ptpaddr, (u32)now.tv_sec, now.tv_nsec);
+	ret = stmmac_init_systime(priv, priv->ptpaddr, (u32)now.tv_sec,
+				  now.tv_nsec);
+	if (ret)
+		goto error;
+
+	priv->systime_flags = systime_flags;
 
 	return 0;
+error:
+	/* Restore previous configuration */
+	stmmac_restore_subsecond_increment(priv, default_addend,
+					   priv->systime_flags);
+
+	return ret;
 }
 
 /**
@@ -7696,18 +7740,23 @@ static int stmmac_dl_ts_coarse_set(struct devlink *dl, u32 id,
 {
 	struct stmmac_devlink_priv *dl_priv = devlink_priv(dl);
 	struct stmmac_priv *priv = dl_priv->stmmac_priv;
+	u32 systime_flags = priv->systime_flags;
+	int ret;
 
-	priv->tsfupdt_coarse = ctx->val.vbool;
-
-	if (priv->tsfupdt_coarse)
-		priv->systime_flags &= ~PTP_TCR_TSCFUPDT;
+	if (ctx->val.vbool)
+		systime_flags &= ~PTP_TCR_TSCFUPDT;
 	else
-		priv->systime_flags |= PTP_TCR_TSCFUPDT;
+		systime_flags |= PTP_TCR_TSCFUPDT;
 
 	/* In Coarse mode, we can use a smaller subsecond increment, let's
 	 * reconfigure the systime, subsecond increment and addend.
 	 */
-	stmmac_update_subsecond_increment(priv);
+	ret = stmmac_update_subsecond_increment(priv, systime_flags);
+	if (ret)
+		return ret;
+
+	priv->tsfupdt_coarse = ctx->val.vbool;
+	priv->systime_flags = systime_flags;
 
 	return 0;
 }

---
base-commit: 58eb1b3325edac42dc6df72c80962bd53a3c8ca7
change-id: 20260920-stmmac-ptp-added-systime-error-bc9566262f2f

Best regards,
-- 
Lorenzo Bianconi <lorenzo.bianconi@xxxxxxxxxxxxxxxx>