[PATCH net v2] net: stmmac: do not overwrite phc_index when no PTP clock is registered

[PATCH net v2] net: stmmac: do not overwrite phc_index when no PTP clock is registered

[Lorenzo Bianconi]

stmmac_get_ts_info() reports phc_index as 0 when hardware timestamping
is supported but no PTP clock has been registered yet (e.g. while the
interface is down). Zero is a valid PHC index and would make userspace
resolve the wrong clock; the absence of a clock should be reported as
-1.

The ethtool core already initializes phc_index to -1 before invoking
the get_ts_info callback (ethtool_init_tsinfo()), so just drop the
erroneous assignment.

Fixes: 9364fa7fcf12 ("net: stmmac: Remove setting of RX software timestamp")
Reviewed-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
Reviewed-by: Rahul Rameshbabu <rrameshbabu@nvidia.com>
Signed-off-by: Lorenzo Bianconi <lorenzo.bianconi@oss.qualcomm.com>
---
Changes in v2:
- Drop phc_index assignment to -1
- Link to v1: https://lore.kernel.org/r/20260912-stmmac-fix-phc_index-v1-1-26e1ead25324@oss.qualcomm.com
---
 drivers/net/ethernet/stmicro/stmmac/stmmac_ethtool.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_ethtool.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_ethtool.c
index 154cc0c7623d..1be5310ca766 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_ethtool.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_ethtool.c
@@ -1016,8 +1016,6 @@ static int stmmac_get_ts_info(struct net_device *dev,
 
 		if (priv->ptp_clock)
 			info->phc_index = ptp_clock_index(priv->ptp_clock);
-		else
-			info->phc_index = 0;
 
 		info->tx_types = (1 << HWTSTAMP_TX_OFF) | (1 << HWTSTAMP_TX_ON);
 

---
base-commit: 78445023439506ebd83b86d40b1e428a3b309d4a
change-id: 20260912-stmmac-fix-phc_index-1ebf19cce076

Best regards,
-- 
Lorenzo Bianconi <lorenzo.bianconi@oss.qualcomm.com>

Re: [PATCH net v2] net: stmmac: do not overwrite phc_index when no PTP clock is registered

[Gal Pressman]

On 14/09/2026 10:41, Lorenzo Bianconi wrote:
> stmmac_get_ts_info() reports phc_index as 0 when hardware timestamping
> is supported but no PTP clock has been registered yet (e.g. while the
> interface is down). Zero is a valid PHC index and would make userspace
> resolve the wrong clock; the absence of a clock should be reported as
> -1.
> 
> The ethtool core already initializes phc_index to -1 before invoking
> the get_ts_info callback (ethtool_init_tsinfo()), so just drop the
> erroneous assignment.
> 
> Fixes: 9364fa7fcf12 ("net: stmmac: Remove setting of RX software timestamp")
> Reviewed-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
> Reviewed-by: Rahul Rameshbabu <rrameshbabu@nvidia.com>
> Signed-off-by: Lorenzo Bianconi <lorenzo.bianconi@oss.qualcomm.com>
> ---
> Changes in v2:
> - Drop phc_index assignment to -1
> - Link to v1: https://lore.kernel.org/r/20260912-stmmac-fix-phc_index-v1-1-26e1ead25324@oss.qualcomm.com
Thanks Lorenzo!
Reviewed-by: Gal Pressman <gal@nvidia.com>

Re: [PATCH net v2] net: stmmac: do not overwrite phc_index when no PTP clock is registered

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net.git (main)
by Jakub Kicinski <kuba@kernel.org>:

On Mon, 14 Sep 2026 09:41:07 +0200 you wrote:
> stmmac_get_ts_info() reports phc_index as 0 when hardware timestamping
> is supported but no PTP clock has been registered yet (e.g. while the
> interface is down). Zero is a valid PHC index and would make userspace
> resolve the wrong clock; the absence of a clock should be reported as
> -1.
> 
> The ethtool core already initializes phc_index to -1 before invoking
> the get_ts_info callback (ethtool_init_tsinfo()), so just drop the
> erroneous assignment.
> 
> [...]

Here is the summary with links:
  - [net,v2] net: stmmac: do not overwrite phc_index when no PTP clock is registered
    https://git.kernel.org/netdev/net/c/f0ef4b1eaed0

You are awesome, thank you!
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