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

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Message-ID: <20200130120730.GA60572@ranger.igk.intel.com>
Date:   Thu, 30 Jan 2020 13:07:30 +0100
From:   Maciej Fijalkowski <maciej.fijalkowski@...el.com>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     Robert Jones <rjones@...eworks.com>,
        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 Thu, Jan 30, 2020 at 09:10:55AM -0800, Jakub Kicinski wrote:
> 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);

Another quick look: use snprintf so that you won't overflow the
bgx->irq_name in case bgx->bgx_id has some weird big number.

> > +	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;
> > +}