Re: [PATCH V3 1/3] net: stmmac: Fix PTP ref clock for Tegra234

[Krzysztof Kozlowski <krzk@kernel.org>]

On Wed, Mar 25, 2026 at 01:58:09PM +0000, Jon Hunter wrote:
> Since commit 030ce919e114 ("net: stmmac: make sure that ptp_rate is not
> 0 before configuring timestamping") was added the following error is
> observed on Tegra234:
> 
>  ERR KERN tegra-mgbe 6800000.ethernet eth0: Invalid PTP clock rate
>  WARNING KERN tegra-mgbe 6800000.ethernet eth0: PTP init failed
> 
> It turns out that the Tegra234 device-tree binding defines the PTP ref
> clock name as 'ptp-ref' and not 'ptp_ref' and the above commit now
> exposes this and that the PTP clock is not configured correctly.
> 
> In order to update device-tree to use the correct 'ptp_ref' name, update
> the Tegra MGBE driver to use 'ptp_ref' by default and fallback to using
> 'ptp-ref' if 'ptp_ref' is not found.
> 
> Fixes: d8ca113724e7 ("net: stmmac: tegra: Add MGBE support")
> Signed-off-by: Jon Hunter <jonathanh@nvidia.com>
> ---
>  .../net/ethernet/stmicro/stmmac/dwmac-tegra.c | 19 +++++++++++++++++--
>  1 file changed, 17 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac-tegra.c b/drivers/net/ethernet/stmicro/stmmac/dwmac-tegra.c
> index b4b39e6a169e..ec18ee46889f 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/dwmac-tegra.c
> +++ b/drivers/net/ethernet/stmicro/stmmac/dwmac-tegra.c
> @@ -9,7 +9,7 @@
>  #include "stmmac_platform.h"
>  
>  static const char *const mgbe_clks[] = {
> -	"rx-pcs", "tx", "tx-pcs", "mac-divider", "mac", "mgbe", "ptp-ref", "mac"
> +	"rx-pcs", "tx", "tx-pcs", "mac-divider", "mac", "mgbe", "ptp_ref", "mac"
>  };
>  
>  struct tegra_mgbe {
> @@ -216,6 +216,7 @@ static int tegra_mgbe_probe(struct platform_device *pdev)
>  	struct plat_stmmacenet_data *plat;
>  	struct stmmac_resources res;
>  	struct tegra_mgbe *mgbe;
> +	bool use_legacy_ptp;
>  	int irq, err, i;
>  	u32 value;
>  
> @@ -257,9 +258,23 @@ static int tegra_mgbe_probe(struct platform_device *pdev)
>  	if (!mgbe->clks)
>  		return -ENOMEM;
>  
> -	for (i = 0; i <  ARRAY_SIZE(mgbe_clks); i++)
> +	/*
> +	 * Older device-trees use 'ptp-ref' rather than 'ptp_ref'.
> +	 * Fall back to the legacy name when 'ptp_ref' is absent.
> +	 */
> +	use_legacy_ptp = of_property_match_string(pdev->dev.of_node,
> +						  "clock-names", "ptp_ref") < 0;
> +
> +	for (i = 0; i < ARRAY_SIZE(mgbe_clks); i++) {
>  		mgbe->clks[i].id = mgbe_clks[i];
>  
> +		if (use_legacy_ptp && !strcmp(mgbe_clks[i], "ptp_ref")) {

Why index 0 is not valid? And why -EINVAL would be considered as legacy
clock present?

> +			dev_warn(mgbe->dev,
> +				 "Device-tree update needed for PTP clock!\n");
> +			mgbe->clks[i].id = "ptp-ref";

Best regards,
Krzysztof