linux-kernel - Re: [PATCH net-next v3 2/3] net: stmmac: Add glue driver for Motorcomm YT6801 ethernet controller

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Message-ID: <aSSspDCPM_5-l24a@shell.armlinux.org.uk>
Date: Mon, 24 Nov 2025 19:06:12 +0000
From: "Russell King (Oracle)" <linux@...linux.org.uk>
To: Yao Zi <ziyao@...root.org>
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>,
	Frank <Frank.Sae@...or-comm.com>,
	Heiner Kallweit <hkallweit1@...il.com>,
	Vladimir Oltean <vladimir.oltean@....com>,
	Choong Yong Liang <yong.liang.choong@...ux.intel.com>,
	Chen-Yu Tsai <wens@...e.org>, Jisheng Zhang <jszhang@...nel.org>,
	Furong Xu <0x1207@...il.com>, linux-kernel@...r.kernel.org,
	netdev@...r.kernel.org, Mingcong Bai <jeffbai@...c.io>,
	Kexy Biscuit <kexybiscuit@...c.io>, Runhua He <hua@...c.io>,
	Xi Ruoyao <xry111@...111.site>
Subject: Re: [PATCH net-next v3 2/3] net: stmmac: Add glue driver for
 Motorcomm YT6801 ethernet controller

On Mon, Nov 24, 2025 at 04:32:10PM +0000, Yao Zi wrote:
> +static int motorcomm_setup_irq(struct pci_dev *pdev,
> +			       struct stmmac_resources *res,
> +			       struct plat_stmmacenet_data *plat)
> +{
> +	int ret;
> +
> +	ret = pci_alloc_irq_vectors(pdev, 6, 6, PCI_IRQ_MSIX);
> +	if (ret > 0) {
> +		res->rx_irq[0]	= pci_irq_vector(pdev, 0);
> +		res->tx_irq[0]	= pci_irq_vector(pdev, 4);
> +		res->irq	= pci_irq_vector(pdev, 5);
> +
> +		plat->flags |= STMMAC_FLAG_MULTI_MSI_EN;
> +
> +		return 0;
> +	}
> +
> +	dev_info(&pdev->dev, "failed to allocate MSI-X vector: %d\n", ret);
> +	dev_info(&pdev->dev, "try MSI instead\n");
> +
> +	ret = pci_alloc_irq_vectors(pdev, 1, 1, PCI_IRQ_MSI);
> +	if (ret < 0)
> +		return dev_err_probe(&pdev->dev, ret,
> +				     "failed to allocate MSI\n");
> +
> +	res->irq = pci_irq_vector(pdev, 0);
> +
> +	return 0;
> +}
> +
> +static int motorcomm_probe(struct pci_dev *pdev, const struct pci_device_id *id)
> +{
...
> +	ret = motorcomm_setup_irq(pdev, &res, plat);
> +	if (ret)
> +		return dev_err_probe(&pdev->dev, ret, "failed to setup IRQ\n");
> +
> +	motorcomm_init(priv);
> +
> +	res.addr = priv->base + GMAC_OFFSET;
> +
> +	return stmmac_dvr_probe(&pdev->dev, plat, &res);

If stmmac_dvr_probe() fails, then it will return an error code. This
leaves the PCI MSI interrupt allocated...

> +}
> +
> +static void motorcomm_remove(struct pci_dev *pdev)
> +{
> +	stmmac_dvr_remove(&pdev->dev);
> +	pci_free_irq_vectors(pdev);

... which stood out because of the presence of this function doing
stuff after the call to stmmac_dvr_remove().

So... reviewing the other stmmac PCI drivers:

- dwmac-intel calls pci_alloc_irq_vectors() but does not call
  pci_free_irq_vectors(). This looks like a bug.
- dwmac-intel calls pcim_enable_device() in its probe function, and
  also its intel_eth_pci_resume() - pcim_enable_device() is the devres
  managed function, so we end up adding more and more devres entries
  each time intel_eth_pci_resume() is resumed. Note that
  intel_eth_pci_suspend() doesn't disable the device. So, this should
  probably be the non-devres version.
- dwmac-loongson looks sane, but the checks for ld->multichan before
  calling loongson_dwmac_msi_clear() look unnecessary, as
  pci_free_irq_vectors() can be safely called even if MSI/MSI-X have
  not been (successfully) allocated.

So, I wonder whether there is scope to have a common way to clean up
PCI drivers. Could you look into this please?

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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