linux-kernel - Re: [PATCH] net: stmmac: add explicit check and error on invalid PTP clock rate

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Message-ID: <8f1928e5-472e-4140-875c-6b5743be8fd3@linux.dev>
Date: Mon, 26 May 2025 10:22:47 +0800
From: Yanteng Si <si.yanteng@...ux.dev>
To: Alexis Lothoré <alexis.lothore@...tlin.com>,
 Alexandre Torgue <alexandre.torgue@...s.st.com>,
 Jose Abreu <joabreu@...opsys.com>, 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>,
 Richard Cochran <richardcochran@...il.com>
Cc: Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
 Maxime Chevallier <maxime.chevallier@...tlin.com>, netdev@...r.kernel.org,
 linux-stm32@...md-mailman.stormreply.com,
 linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] net: stmmac: add explicit check and error on invalid PTP
 clock rate

在 5/23/25 7:46 PM, Alexis LothorÃ© 写道:
> While some platforms implementing dwmac open-code the clk_ptp_rate
> value, some others dynamically retrieve the value at runtime. If the
> retrieved value happens to be 0 for any reason, it will eventually
> propagate up to PTP initialization when bringing up the interface,
> leading to a divide by 0:
> 
>   Division by zero in kernel.
>   CPU: 1 UID: 0 PID: 1 Comm: swapper/0 Not tainted 6.12.30-00001-g48313bd5768a #22
>   Hardware name: STM32 (Device Tree Support)
>   Call trace:
>    unwind_backtrace from show_stack+0x18/0x1c
>    show_stack from dump_stack_lvl+0x6c/0x8c
>    dump_stack_lvl from Ldiv0_64+0x8/0x18
>    Ldiv0_64 from stmmac_init_tstamp_counter+0x190/0x1a4
>    stmmac_init_tstamp_counter from stmmac_hw_setup+0xc1c/0x111c
>    stmmac_hw_setup from __stmmac_open+0x18c/0x434
>    __stmmac_open from stmmac_open+0x3c/0xbc
>    stmmac_open from __dev_open+0xf4/0x1ac
>    __dev_open from __dev_change_flags+0x1cc/0x224
>    __dev_change_flags from dev_change_flags+0x24/0x60
>    dev_change_flags from ip_auto_config+0x2e8/0x11a0
>    ip_auto_config from do_one_initcall+0x84/0x33c
>    do_one_initcall from kernel_init_freeable+0x1b8/0x214
>    kernel_init_freeable from kernel_init+0x24/0x140
>    kernel_init from ret_from_fork+0x14/0x28
>   Exception stack(0xe0815fb0 to 0xe0815ff8)
> 
> Prevent this division by 0 by adding an explicit check and error log
> about the actual issue.

 From your description, I cannot determine the scope
of "some platforms". My point is: if there are only
a few platforms, can we find a way to handle this in
the directory of the corresponding platform?

And there need a Fixes tag.

Thanks,
Yanteng
> 
> Signed-off-by: Alexis Lothoré <alexis.lothore@...tlin.com>
> ---
>   drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 5 +++++
>   1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> index 918d7f2e8ba992208d7d6521a1e9dba01086058f..f68e3ece919cc88d0bf199a394bc7e44b5dee095 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> @@ -835,6 +835,11 @@ int stmmac_init_tstamp_counter(struct stmmac_priv *priv, u32 systime_flags)
>   	if (!(priv->dma_cap.time_stamp || priv->dma_cap.atime_stamp))
>   		return -EOPNOTSUPP;
>   
> +	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;
>   
> 
> ---
> base-commit: e0e2f78243385e7188a57fcfceb6a19f723f1dff
> change-id: 20250522-stmmac_tstamp_div-f55112f06029
> 
> Best regards,