netdev - Re: [PATCH net-next v8 07/11] net: stmmac: dwmac-loongson: Add multi-channel supports for loongson

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Message-ID: <7myfmz72mdp74k3pjtv6gmturdtm7pkghcwpom62hl52eafval@wmbtdwm5kitp>
Date: Wed, 3 Apr 2024 15:03:55 +0300
From: Serge Semin <fancer.lancer@...il.com>
To: Yanteng Si <siyanteng@...ngson.cn>
Cc: hkallweit1@...il.com, andrew@...n.ch, peppe.cavallaro@...com, 
	alexandre.torgue@...s.st.com, joabreu@...opsys.com, Jose.Abreu@...opsys.com, 
	chenhuacai@...ngson.cn, linux@...linux.org.uk, guyinggang@...ngson.cn, 
	netdev@...r.kernel.org, chris.chenfeiyang@...il.com
Subject: Re: [PATCH net-next v8 07/11] net: stmmac: dwmac-loongson: Add
 multi-channel supports for loongson

On Wed, Apr 03, 2024 at 04:09:21PM +0800, Yanteng Si wrote:
> 
> 在 2024/3/23 02:47, Serge Semin 写道:
> > +static int loongson_dwmac_config_multi_msi(struct pci_dev *pdev,
> > +					   struct plat_stmmacenet_data *plat,
> > +					   struct stmmac_resources *res)
> > +{
> > +	int i, ret, vecs;
> > +
> > +	/* INT NAME | MAC | CH7 rx | CH7 tx | ... | CH0 rx | CH0 tx |
> > +	 * --------- ----- -------- --------  ...  -------- --------
> > +	 * IRQ NUM  |  0  |   1    |   2    | ... |   15   |   16   |
> > +	 */
> > +	vecs = plat->rx_queues_to_use + plat->tx_queues_to_use + 1;
> > +	ret = pci_alloc_irq_vectors(pdev, 1, vecs, PCI_IRQ_MSI | PCI_IRQ_LEGACY);
> > +	if (ret < 0) {
> > +		dev_err(&pdev->dev, "Failed to allocate PCI IRQs\n");
> > +		return ret;
> > +	} else if (ret >= vecs) {
> > +		for (i = 0; i < plat->rx_queues_to_use; i++) {
> > +			res->rx_irq[CHANNELS_NUM - 1 - i] =
> > +				pci_irq_vector(pdev, 1 + i * 2);
> > +		}
> > +		for (i = 0; i < plat->tx_queues_to_use; i++) {
> > +			res->tx_irq[CHANNELS_NUM - 1 - i] =
> > +				pci_irq_vector(pdev, 2 + i * 2);
> > +		}
> > +
> > +		plat->flags |= STMMAC_FLAG_MULTI_MSI_EN;
> > +	}
> > +
> > +	res->irq = pci_irq_vector(pdev, 0);
> > +
> > +	return 0;
> > +}
> > 
> > Thus in case if for some reason you were able to allocate less MSI
> > IRQs than required you'll still be able to use them. The legacy IRQ
> > will be also available in case if MSI failed to be allocated.
> 
> Great, we will consider doing this in the future, but at this stage, we
> don't want to add too much complexity.

This comment isn't about complexity. Moreover the code in my comment
is simpler since the function is more coherent and doesn't have the
redundant dependencies from the node-pointer and the
loongson_dwmac_config_legacy() function. In addition it provides more
flexible solution in case if there were less MSI vectors allocated
then required.

-Serge(y)

> 
> 
> Thanks,
> 
> Yanteng
>