linux-kernel - Re: [PATCH v2 2/3] net: stmmac: Add interconnect support

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Message-ID: <483b77c7-e90f-42e1-a8b8-372845d8de62@lunn.ch>
Date: Fri, 28 Jun 2024 22:12:04 +0200
From: Andrew Lunn <andrew@...n.ch>
To: Sagar Cheluvegowda <quic_scheluve@...cinc.com>
Cc: Krzysztof Kozlowski <krzk@...nel.org>, Vinod Koul <vkoul@...nel.org>,
	Alexandre Torgue <alexandre.torgue@...s.st.com>,
	Jose Abreu <joabreu@...opsys.com>,
	"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>,
	Russell King <linux@...linux.org.uk>, Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Bhupesh Sharma <bhupesh.sharma@...aro.org>, kernel@...cinc.com,
	Andrew Halaney <ahalaney@...hat.com>, linux-arm-msm@...r.kernel.org,
	netdev@...r.kernel.org, linux-stm32@...md-mailman.stormreply.com,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	devicetree@...r.kernel.org
Subject: Re: [PATCH v2 2/3] net: stmmac: Add interconnect support

> >> @@ -642,6 +642,18 @@ stmmac_probe_config_dt(struct platform_device *pdev, u8 *mac)
> >>  		dev_dbg(&pdev->dev, "PTP rate %d\n", plat->clk_ptp_rate);
> >>  	}
> >>  
> >> +	plat->axi_icc_path = devm_of_icc_get(&pdev->dev, "axi");
> >> +	if (IS_ERR(plat->axi_icc_path)) {
> >> +		ret = (void *)plat->axi_icc_path;
> >> +		goto error_hw_init;
> > 
> > This sounds like an ABI break. Considering the interconnects are not
> > required by the binding, are you sure this behaves correctly without
> > interconnects in DTS?
> >
> > Best regards,
> > Krzysztof
> > 
> Yes, i did check without the interconnect entries in the dtsi and
> things are working fine, devm_of_icc_get is properly clearing out
> all the references in the case when "interconnects" are not present
> in the dtsi.

So the relevant code is:

https://elixir.bootlin.com/linux/latest/source/drivers/interconnect/core.c#L566

	/*
	 * When the consumer DT node do not have "interconnects" property
	 * return a NULL path to skip setting constraints.
	 */
	if (!of_property_present(np, "interconnects"))
		return NULL;

The naming of of_icc_get() and devm_of_icc_get() is not
great. Typically this behaviour of not giving an error if it is
missing would mean the functions would be of_icc_get_optional() and
devm_of_icc_get_optional(), e.g. we have clk_get_optional(),
gpiod_get_optional(), regulator_get_optional(), etc.

	Andrew