Re: [PATCH net] net: stmmac: dwmac-rk: Ensure clk_phy doesn't contain invalid address

From: Chaoyi Chen <chaoyi.chen@rock-chips.com>
To: "Russell King (Oracle)" <linux@armlinux.org.uk>,
	Yao Zi <ziyao@disroot.org>
Cc: Andrew Lunn <andrew+netdev@lunn.ch>,
	"David S. Miller" <davem@davemloft.net>,
	Eric Dumazet <edumazet@google.com>,
	Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
	Jonas Karlman <jonas@kwiboo.se>,
	David Wu <david.wu@rock-chips.com>,
	netdev@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org, linux-rockchip@lists.infradead.org
Subject: Re: [PATCH net] net: stmmac: dwmac-rk: Ensure clk_phy doesn't contain invalid address
Date: Thu, 4 Sep 2025 19:03:10 +0800	[thread overview]
Message-ID: <b5fbeb3f-9962-444d-85b3-3b8a11f69266@rock-chips.com> (raw)
In-Reply-To: <aLlwv3v8ACha8b-3@shell.armlinux.org.uk>

On 9/4/2025 6:58 PM, Russell King (Oracle) wrote:
> On Thu, Sep 04, 2025 at 03:12:24AM +0000, Yao Zi wrote:
>>   	if (plat->phy_node) {
>>   		bsp_priv->clk_phy = of_clk_get(plat->phy_node, 0);
>>   		ret = PTR_ERR_OR_ZERO(bsp_priv->clk_phy);
>> -		/* If it is not integrated_phy, clk_phy is optional */
>> +		/*
>> +		 * If it is not integrated_phy, clk_phy is optional. But we must
>> +		 * set bsp_priv->clk_phy to NULL if clk_phy isn't proivded, or
>> +		 * the error code could be wrongly taken as an invalid pointer.
>> +		 */
> I'm concerned by this. This code is getting the first clock from the DT
> description of the PHY. We don't know what type of PHY it is, or what
> the DT description of that PHY might suggest that the first clock would
> be.
>
> However, we're geting it and setting it to 50MHz. What if the clock is
> not what we think it is?

We only set integrated_phy to 50M, which are all known targets. For external PHYs, we do not perform frequency settings.

>
> I'm not sure we should be delving in to some other device's DT
> properties to then get resources that it _uses_ to then effectively
> take control those resources.
>
> I think we need way more detail on what's going on. Commit da114122b83
> merely stated:
>
>      For external phy, clk_phy should be optional, and some external phy
>      need the clock input from clk_phy. This patch adds support for setting
>      clk_phy for external phy.
>
> If the external PHY requires a clock supplied to it, shouldn't the PHY
> driver itself be getting that clock and setting it appropriately?
>

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