netdev - Re: [PATCH] net: stmmac: Fix PTP ref clock for Tegra234

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Message-ID: <aEqyrWDPykceDM2x@a5393a930297>
Date: Thu, 12 Jun 2025 10:57:49 +0000
From: Subbaraya Sundeep <sbhatta@...vell.com>
To: Jon Hunter <jonathanh@...dia.com>
CC: Andrew Lunn <andrew+netdev@...n.ch>,
        "David S . Miller"
	<davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski
	<kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Maxime Coquelin
	<mcoquelin.stm32@...il.com>,
        Alexandre Torgue <alexandre.torgue@...s.st.com>,
        <netdev@...r.kernel.org>, <linux-stm32@...md-mailman.stormreply.com>,
        <linux-tegra@...r.kernel.org>,
        Alexis Lothorrr <alexis.lothore@...tlin.com>
Subject: Re: [PATCH] net: stmmac: Fix PTP ref clock for Tegra234

Hi,

On 2025-06-12 at 06:20:32, Jon Hunter (jonathanh@...dia.com) 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.
> 
> Ideally, we would rename the PTP ref clock for Tegra234 to fix this but
> this will break backward compatibility with existing device-tree blobs.
> Therefore, fix this by using the name 'ptp-ref' for devices that are
> compatible with 'nvidia,tegra234-mgbe'.
AFAIU for Tegra234 device from the beginning, entry in dts is ptp-ref.
Since driver is looking for ptp_ref it is getting 0 hence the crash
and after the commit 030ce919e114 result is Invalid error instead of crash.
For me PTP is not working for Tegra234 from day 1 so why to bother about
backward compatibility and instead fix dts.
Please help me understand it has been years I worked on dts.

Thanks,
Sundeep
> 
> Fixes: d8ca113724e7 ("net: stmmac: tegra: Add MGBE support")
> Signed-off-by: Jon Hunter <jonathanh@...dia.com>
> ---
>  drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c
> index b80c1efdb323..f82a7d55ea0a 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c
> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c
> @@ -635,8 +635,12 @@ stmmac_probe_config_dt(struct platform_device *pdev, u8 *mac)
>  	}
>  	clk_prepare_enable(plat->pclk);
>  
> +	if (of_device_is_compatible(np, "nvidia,tegra234-mgbe"))
> +		plat->clk_ptp_ref = devm_clk_get(&pdev->dev, "ptp-ref");
> +	else
> +		plat->clk_ptp_ref = devm_clk_get(&pdev->dev, "ptp_ref");
> +
>  	/* Fall-back to main clock in case of no PTP ref is passed */
> -	plat->clk_ptp_ref = devm_clk_get(&pdev->dev, "ptp_ref");
>  	if (IS_ERR(plat->clk_ptp_ref)) {
>  		plat->clk_ptp_rate = clk_get_rate(plat->stmmac_clk);
>  		plat->clk_ptp_ref = NULL;
> -- 
> 2.43.0
>