netdev - Re: [PATCH net] net: thunderx: workaround BGX TX Underflow issue

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Date:   Thu, 30 Jan 2020 09:10:55 -0800
From:   Jakub Kicinski <kuba@...nel.org>
To:     Robert Jones <rjones@...eworks.com>
Cc:     Sunil Goutham <sgoutham@...vell.com>,
        Robert Richter <rrichter@...vell.com>,
        David Miller <davem@...emloft.net>,
        linux-arm-kernel@...ts.infradead.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, Tim Harvey <tharvey@...eworks.com>
Subject: Re: [PATCH net] net: thunderx: workaround BGX TX Underflow issue

On Wed, 29 Jan 2020 14:36:09 -0800, Robert Jones wrote:
> From: Tim Harvey <tharvey@...eworks.com>
> 
> While it is not yet understood why a TX underflow can easily occur
> for SGMII interfaces resulting in a TX wedge. It has been found that
> disabling/re-enabling the LMAC resolves the issue.
> 
> Signed-off-by: Tim Harvey <tharvey@...eworks.com>
> Reviewed-by: Robert Jones <rjones@...eworks.com>

Sunil or Robert (i.e. one of the maintainers) will have to review this
patch (as indicated by Dave by marking it with "Needs Review / ACK" in
patchwork).

At a quick look there are some things which jump out at me:

> +static int bgx_register_intr(struct pci_dev *pdev)
> +{
> +	struct bgx *bgx = pci_get_drvdata(pdev);
> +	struct device *dev = &pdev->dev;
> +	int num_vec, ret;
> +
> +	/* Enable MSI-X */
> +	num_vec = pci_msix_vec_count(pdev);
> +	ret = pci_alloc_irq_vectors(pdev, num_vec, num_vec, PCI_IRQ_MSIX);
> +	if (ret < 0) {
> +		dev_err(dev, "Req for #%d msix vectors failed\n", num_vec);
> +		return 1;

Please propagate real error codes, or make this function void as the
caller never actually checks the return value.

> +	}
> +	sprintf(bgx->irq_name, "BGX%d", bgx->bgx_id);
> +	ret = request_irq(pci_irq_vector(pdev, GMPX_GMI_TX_INT),

There is a alloc_irq and request_irq call added in this patch but there
is never any freeing. Are you sure this is fine? Devices can be
reprobed (unbound and bound to drivers via sysfs).

> +		bgx_intr_handler, 0, bgx->irq_name, bgx);

Please align the continuation line with the opening bracket (checkpatch
--strict should help catch this).

> +	if (ret)
> +		return 1;
> +
> +	return 0;
> +}