linux-kernel - Re: [PATCH v5 05/14] PCI: Add pcie_print_link_status() to log link speed and whether it's limited

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Date:   Thu, 12 Apr 2018 21:32:49 -0700
From:   Jakub Kicinski <kubakici@...pl>
To:     Bjorn Helgaas <helgaas@...nel.org>
Cc:     Tal Gilboa <talgi@...lanox.com>,
        Tariq Toukan <tariqt@...lanox.com>,
        Jacob Keller <jacob.e.keller@...el.com>,
        Ariel Elior <ariel.elior@...ium.com>,
        Ganesh Goudar <ganeshgr@...lsio.com>,
        Jeff Kirsher <jeffrey.t.kirsher@...el.com>,
        everest-linux-l2@...ium.com, intel-wired-lan@...ts.osuosl.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-pci@...r.kernel.org
Subject: Re: [PATCH v5 05/14] PCI: Add pcie_print_link_status() to log link
 speed and whether it's limited

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)

Sorry for a very late comment.