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SubjectRe: [PATCH v5 05/14] PCI: Add pcie_print_link_status() to log link speed and whether it's limited
On Thu, Apr 12, 2018 at 09:32:49PM -0700, Jakub Kicinski wrote:
> On Fri, 30 Mar 2018 16:05:18 -0500, Bjorn Helgaas wrote:
> > + if (bw_avail >= bw_cap)
> > + pci_info(dev, "%d Mb/s available bandwidth (%s x%d link)\n",
> > + bw_cap, PCIE_SPEED2STR(speed_cap), width_cap);
> > + else
> > + pci_info(dev, "%d Mb/s available bandwidth, limited by %s x%d link at %s (capable of %d Mb/s with %s x%d link)\n",
> > + bw_avail, PCIE_SPEED2STR(speed), width,
> > + limiting_dev ? pci_name(limiting_dev) : "<unknown>",
> > + bw_cap, PCIE_SPEED2STR(speed_cap), width_cap);
>
> I was just looking at using this new function to print PCIe BW for a
> NIC, but I'm slightly worried that there is nothing in the message that
> says PCIe... For a NIC some people may interpret the bandwidth as NIC
> bandwidth:
>
> [ 39.839989] nfp 0000:04:00.0: Netronome Flow Processor NFP4000/NFP6000 PCIe Card Probe
> [ 39.848943] nfp 0000:04:00.0: 63.008 Gb/s available bandwidth (8 GT/s x8 link)
> [ 39.857146] nfp 0000:04:00.0: RESERVED BARs: 0.0: General/MSI-X SRAM, 0.1: PCIe XPB/MSI-X PBA, 0.4: Explicit0, 0.5: Explicit1, fre4
>
> It's not a 63Gbps NIC... I'm sorry if this was discussed before and I
> didn't find it. Would it make sense to add the "PCIe: " prefix to the
> message like bnx2x used to do? Like:
>
> nfp 0000:04:00.0: PCIe: 63.008 Gb/s available bandwidth (8 GT/s x8 link)

I agree, that does look potentially confusing. How about this:

nfp 0000:04:00.0: 63.008 Gb/s available PCIe bandwidth (8 GT/s x8 link)

I did have to look twice at this before I remembered that we're
printing Gb/s (not GB/s). Most of the references I found on the web
use GB/s when talking about total PCIe bandwidth.

But either way I think it's definitely worth mentioning PCIe
explicitly.

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