linux-kernel - Re: [PATCH net v2] net: stmmac: add clk_prepare

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Message-ID: <4a3a8ba2-2535-461d-a0a5-e29873f538a4@redhat.com>
Date: Tue, 18 Nov 2025 15:30:09 +0100
From: Paolo Abeni <pabeni@...hat.com>
To: Pavel Zhigulin <Pavel.Zhigulin@...persky.com>,
 Andrew Lunn <andrew+netdev@...n.ch>
Cc: "David S. Miller" <davem@...emloft.net>,
 Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>,
 Maxime Coquelin <mcoquelin.stm32@...il.com>,
 Alexandre Torgue <alexandre.torgue@...s.st.com>,
 Maxime Chevallier <maxime.chevallier@...tlin.com>,
 Inochi Amaoto <inochiama@...il.com>,
 Quentin Schulz <quentin.schulz@...rry.de>,
 Joe Hattori <joe@...is.s.u-tokyo.ac.jp>,
 Rayagond Kokatanur <rayagond@...avyalabs.com>,
 Giuseppe CAVALLARO <peppe.cavallaro@...com>, netdev@...r.kernel.org,
 linux-stm32@...md-mailman.stormreply.com,
 linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
 lvc-project@...uxtesting.org
Subject: Re: [PATCH net v2] net: stmmac: add clk_prepare_enable() error
 handling

On 11/14/25 3:23 PM, Pavel Zhigulin wrote:
> The driver previously ignored the return value of 'clk_prepare_enable()'
> for both the CSR clock and the PCLK in 'stmmac_probe_config_dt()' function.
> 
> Add 'clk_prepare_enable()' return value checks.
> 
> Found by Linux Verification Center (linuxtesting.org) with SVACE.
> 
> Fixes: bfab27a146ed ("stmmac: add the experimental PCI support")
> Signed-off-by: Pavel Zhigulin <Pavel.Zhigulin@...persky.com>
> ---
> v2: Fix 'ret' value initialization after build bot notification.
> v1: https://lore.kernel.org/all/20251113134009.79440-1-Pavel.Zhigulin@kaspersky.com/
> 
>  drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c | 11 +++++++++--
>  1 file changed, 9 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c
> index 27bcaae07a7f..8f9eb9683d2b 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c
> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c
> @@ -632,7 +632,9 @@ stmmac_probe_config_dt(struct platform_device *pdev, u8 *mac)
>  			dev_warn(&pdev->dev, "Cannot get CSR clock\n");
>  			plat->stmmac_clk = NULL;
>  		}
> -		clk_prepare_enable(plat->stmmac_clk);
> +		rc = clk_prepare_enable(plat->stmmac_clk);
> +		if (rc < 0)
> +			dev_warn(&pdev->dev, "Cannot enable CSR clock: %d\n", rc);
>  	}
> 
>  	plat->pclk = devm_clk_get_optional(&pdev->dev, "pclk");
> @@ -640,7 +642,12 @@ stmmac_probe_config_dt(struct platform_device *pdev, u8 *mac)
>  		ret = plat->pclk;
>  		goto error_pclk_get;
>  	}
> -	clk_prepare_enable(plat->pclk);
> +	rc = clk_prepare_enable(plat->pclk);
> +	if (rc < 0) {
> +		ret = ERR_PTR(rc);
> +		dev_err(&pdev->dev, "Cannot enable pclk: %d\n", rc);
> +		goto error_pclk_get;
> +	}

It looks like the driver is supposed to handle the
IS_ERR_OR_NULL(plat->pclk) condition. This check could cause regression
on existing setup currently failing to initialize the (optional) clock
and still being functional.

I *think* we are better off without the added checks.

/P