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

2018-04-13 Thread Keller, Jacob E 


> -Original Message-
> From: Bjorn Helgaas [mailto:helg...@kernel.org]
> Sent: Friday, April 13, 2018 7:07 AM
> To: Jakub Kicinski <kubak...@wp.pl>
> Cc: Tal Gilboa <ta...@mellanox.com>; Tariq Toukan <tar...@mellanox.com>;
> Keller, Jacob E <jacob.e.kel...@intel.com>; Ariel Elior 
> <ariel.el...@cavium.com>;
> Ganesh Goudar <ganes...@chelsio.com>; Kirsher, Jeffrey T
> <jeffrey.t.kirs...@intel.com>; everest-linux...@cavium.com; intel-wired-
> l...@lists.osuosl.org; netdev@vger.kernel.org; linux-ker...@vger.kernel.org;
> linux-...@vger.kernel.org
> Subject: Re: [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) : "",
> > > +  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 :04:00.0: Netronome Flow Processor NFP4000/NFP6000
> PCIe Card Probe
> > [   39.848943] nfp :04:00.0: 63.008 Gb/s available bandwidth (8 GT/s x8 
> > link)
> > [   39.857146] nfp :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 :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 :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.

I also agree printing PCIe explicitly is good.

Thanks,
Jake

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

2018-04-13 Thread Bjorn Helgaas 
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) : "",
> > +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 :04:00.0: Netronome Flow Processor NFP4000/NFP6000 
> PCIe Card Probe
> [   39.848943] nfp :04:00.0: 63.008 Gb/s available bandwidth (8 GT/s x8 
> link)
> [   39.857146] nfp :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 :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 :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.

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

2018-04-12 Thread Jakub Kicinski 
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) : "",
> +  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 :04:00.0: Netronome Flow Processor NFP4000/NFP6000 PCIe 
Card Probe
[   39.848943] nfp :04:00.0: 63.008 Gb/s available bandwidth (8 GT/s x8 
link)
[   39.857146] nfp :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 :04:00.0: PCIe: 63.008 Gb/s available bandwidth (8 GT/s x8 link)

Sorry for a very late comment.

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

2018-04-02 Thread Tal Gilboa 

On 4/2/2018 11:25 PM, Keller, Jacob E wrote:




-Original Message-
From: Bjorn Helgaas [mailto:helg...@kernel.org]
Sent: Monday, April 02, 2018 12:58 PM
To: Keller, Jacob E <jacob.e.kel...@intel.com>
Cc: Tal Gilboa <ta...@mellanox.com>; Tariq Toukan <tar...@mellanox.com>; Ariel
Elior <ariel.el...@cavium.com>; Ganesh Goudar <ganes...@chelsio.com>;
Kirsher, Jeffrey T <jeffrey.t.kirs...@intel.com>; everest-linux...@cavium.com;
intel-wired-...@lists.osuosl.org; netdev@vger.kernel.org; linux-
ker...@vger.kernel.org; linux-...@vger.kernel.org
Subject: Re: [PATCH v5 05/14] PCI: Add pcie_print_link_status() to log link 
speed
and whether it's limited

On Mon, Apr 02, 2018 at 04:25:17PM +, Keller, Jacob E wrote:

-Original Message-
From: Bjorn Helgaas [mailto:helg...@kernel.org]
Sent: Friday, March 30, 2018 2:05 PM
To: Tal Gilboa <ta...@mellanox.com>
Cc: Tariq Toukan <tar...@mellanox.com>; Keller, Jacob E
<jacob.e.kel...@intel.com>; Ariel Elior <ariel.el...@cavium.com>; Ganesh
Goudar <ganes...@chelsio.com>; Kirsher, Jeffrey T
<jeffrey.t.kirs...@intel.com>; everest-linux...@cavium.com; intel-wired-
l...@lists.osuosl.org; netdev@vger.kernel.org; linux-ker...@vger.kernel.org;
linux-...@vger.kernel.org
Subject: [PATCH v5 05/14] PCI: Add pcie_print_link_status() to log link speed

and

whether it's limited

From: Tal Gilboa <ta...@mellanox.com>

Add pcie_print_link_status().  This logs the current settings of the link
(speed, width, and total available bandwidth).

If the device is capable of more bandwidth but is limited by a slower
upstream link, we include information about the link that limits the
device's performance.

The user may be able to move the device to a different slot for better
performance.

This provides a unified method for all PCI devices to report status and
issues, instead of each device reporting in a different way, using
different code.

Signed-off-by: Tal Gilboa <ta...@mellanox.com>
[bhelgaas: changelog, reword log messages, print device capabilities when
not limited]
Signed-off-by: Bjorn Helgaas <bhelg...@google.com>
---
  drivers/pci/pci.c   |   29 +
  include/linux/pci.h |1 +
  2 files changed, 30 insertions(+)

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index e00d56b12747..cec7aed09f6b 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -5283,6 +5283,35 @@ u32 pcie_bandwidth_capable(struct pci_dev *dev,
enum pci_bus_speed *speed,
return *width * PCIE_SPEED2MBS_ENC(*speed);
  }

+/**
+ * pcie_print_link_status - Report the PCI device's link speed and width
+ * @dev: PCI device to query
+ *
+ * Report the available bandwidth at the device.  If this is less than the
+ * device is capable of, report the device's maximum possible bandwidth and
+ * the upstream link that limits its performance to less than that.
+ */
+void pcie_print_link_status(struct pci_dev *dev)
+{
+   enum pcie_link_width width, width_cap;
+   enum pci_bus_speed speed, speed_cap;
+   struct pci_dev *limiting_dev = NULL;
+   u32 bw_avail, bw_cap;
+
+   bw_cap = pcie_bandwidth_capable(dev, _cap, _cap);
+   bw_avail = pcie_bandwidth_available(dev, _dev, ,
);
+
+   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) : "",
+bw_cap, PCIE_SPEED2STR(speed_cap), width_cap);
+}


Personally, I would make thic last one a pci_warn() to indicate it at a
higher log level, but I'm  ok with the wording, and if consensus is that
this should be at info, I'm ok with that.


Tal's original patch did have a pci_warn() here, and we went back and
forth a bit.  They get bug reports when a device doesn't perform as
expected, which argues for pci_warn().  But they also got feedback
saying warnings are a bit too much, which argues for pci_info() [1]

I don't have a really strong opinion either way.  I have a slight
preference for info because the user may not be able to do anything
about it (there may not be a faster slot available), and I think
distros are usually configured so a warning interrupts the smooth
graphical boot.

It looks like mlx4, fm10k, and ixgbe currently use warnings, while
bnx2x, bnxt_en, and cxgb4 use info.  It's a tie so far :)

[1] https://lkml.kernel.org/r/e47f3628-b56c-4d0a-f18b-
5ffaf261c...@mellanox.com



With that information, I'm fine with the proposal to display this as only an 
info. The message is still printed and can be used for debugging purposes, and 
I think that's really enough.


Here's a proposal for printing the bandwidth as "x.xxx Gb/s":


Nice, I like that also.

Regards,
Jake



Same here for both.

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

2018-04-02 Thread Keller, Jacob E 


> -Original Message-
> From: Bjorn Helgaas [mailto:helg...@kernel.org]
> Sent: Monday, April 02, 2018 12:58 PM
> To: Keller, Jacob E <jacob.e.kel...@intel.com>
> Cc: Tal Gilboa <ta...@mellanox.com>; Tariq Toukan <tar...@mellanox.com>; Ariel
> Elior <ariel.el...@cavium.com>; Ganesh Goudar <ganes...@chelsio.com>;
> Kirsher, Jeffrey T <jeffrey.t.kirs...@intel.com>; everest-linux...@cavium.com;
> intel-wired-...@lists.osuosl.org; netdev@vger.kernel.org; linux-
> ker...@vger.kernel.org; linux-...@vger.kernel.org
> Subject: Re: [PATCH v5 05/14] PCI: Add pcie_print_link_status() to log link 
> speed
> and whether it's limited
> 
> On Mon, Apr 02, 2018 at 04:25:17PM +, Keller, Jacob E wrote:
> > > -Original Message-
> > > From: Bjorn Helgaas [mailto:helg...@kernel.org]
> > > Sent: Friday, March 30, 2018 2:05 PM
> > > To: Tal Gilboa <ta...@mellanox.com>
> > > Cc: Tariq Toukan <tar...@mellanox.com>; Keller, Jacob E
> > > <jacob.e.kel...@intel.com>; Ariel Elior <ariel.el...@cavium.com>; Ganesh
> > > Goudar <ganes...@chelsio.com>; Kirsher, Jeffrey T
> > > <jeffrey.t.kirs...@intel.com>; everest-linux...@cavium.com; intel-wired-
> > > l...@lists.osuosl.org; netdev@vger.kernel.org; 
> > > linux-ker...@vger.kernel.org;
> > > linux-...@vger.kernel.org
> > > Subject: [PATCH v5 05/14] PCI: Add pcie_print_link_status() to log link 
> > > speed
> and
> > > whether it's limited
> > >
> > > From: Tal Gilboa <ta...@mellanox.com>
> > >
> > > Add pcie_print_link_status().  This logs the current settings of the link
> > > (speed, width, and total available bandwidth).
> > >
> > > If the device is capable of more bandwidth but is limited by a slower
> > > upstream link, we include information about the link that limits the
> > > device's performance.
> > >
> > > The user may be able to move the device to a different slot for better
> > > performance.
> > >
> > > This provides a unified method for all PCI devices to report status and
> > > issues, instead of each device reporting in a different way, using
> > > different code.
> > >
> > > Signed-off-by: Tal Gilboa <ta...@mellanox.com>
> > > [bhelgaas: changelog, reword log messages, print device capabilities when
> > > not limited]
> > > Signed-off-by: Bjorn Helgaas <bhelg...@google.com>
> > > ---
> > >  drivers/pci/pci.c   |   29 +
> > >  include/linux/pci.h |1 +
> > >  2 files changed, 30 insertions(+)
> > >
> > > diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> > > index e00d56b12747..cec7aed09f6b 100644
> > > --- a/drivers/pci/pci.c
> > > +++ b/drivers/pci/pci.c
> > > @@ -5283,6 +5283,35 @@ u32 pcie_bandwidth_capable(struct pci_dev *dev,
> > > enum pci_bus_speed *speed,
> > >   return *width * PCIE_SPEED2MBS_ENC(*speed);
> > >  }
> > >
> > > +/**
> > > + * pcie_print_link_status - Report the PCI device's link speed and width
> > > + * @dev: PCI device to query
> > > + *
> > > + * Report the available bandwidth at the device.  If this is less than 
> > > the
> > > + * device is capable of, report the device's maximum possible bandwidth 
> > > and
> > > + * the upstream link that limits its performance to less than that.
> > > + */
> > > +void pcie_print_link_status(struct pci_dev *dev)
> > > +{
> > > + enum pcie_link_width width, width_cap;
> > > + enum pci_bus_speed speed, speed_cap;
> > > + struct pci_dev *limiting_dev = NULL;
> > > + u32 bw_avail, bw_cap;
> > > +
> > > + bw_cap = pcie_bandwidth_capable(dev, _cap, _cap);
> > > + bw_avail = pcie_bandwidth_available(dev, _dev, ,
> > > );
> > > +
> > > + 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) : "",
> > > +  bw_cap, PCIE_SPEED2STR(speed_cap), width_cap);
> > > +}
> >
> > P

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

2018-04-02 Thread Bjorn Helgaas 
On Mon, Apr 02, 2018 at 04:25:17PM +, Keller, Jacob E wrote:
> > -Original Message-
> > From: Bjorn Helgaas [mailto:helg...@kernel.org]
> > Sent: Friday, March 30, 2018 2:05 PM
> > To: Tal Gilboa 
> > Cc: Tariq Toukan ; Keller, Jacob E
> > ; Ariel Elior ; Ganesh
> > Goudar ; Kirsher, Jeffrey T
> > ; everest-linux...@cavium.com; intel-wired-
> > l...@lists.osuosl.org; netdev@vger.kernel.org; linux-ker...@vger.kernel.org;
> > linux-...@vger.kernel.org
> > Subject: [PATCH v5 05/14] PCI: Add pcie_print_link_status() to log link 
> > speed and
> > whether it's limited
> > 
> > From: Tal Gilboa 
> > 
> > Add pcie_print_link_status().  This logs the current settings of the link
> > (speed, width, and total available bandwidth).
> > 
> > If the device is capable of more bandwidth but is limited by a slower
> > upstream link, we include information about the link that limits the
> > device's performance.
> > 
> > The user may be able to move the device to a different slot for better
> > performance.
> > 
> > This provides a unified method for all PCI devices to report status and
> > issues, instead of each device reporting in a different way, using
> > different code.
> > 
> > Signed-off-by: Tal Gilboa 
> > [bhelgaas: changelog, reword log messages, print device capabilities when
> > not limited]
> > Signed-off-by: Bjorn Helgaas 
> > ---
> >  drivers/pci/pci.c   |   29 +
> >  include/linux/pci.h |1 +
> >  2 files changed, 30 insertions(+)
> > 
> > diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> > index e00d56b12747..cec7aed09f6b 100644
> > --- a/drivers/pci/pci.c
> > +++ b/drivers/pci/pci.c
> > @@ -5283,6 +5283,35 @@ u32 pcie_bandwidth_capable(struct pci_dev *dev,
> > enum pci_bus_speed *speed,
> > return *width * PCIE_SPEED2MBS_ENC(*speed);
> >  }
> > 
> > +/**
> > + * pcie_print_link_status - Report the PCI device's link speed and width
> > + * @dev: PCI device to query
> > + *
> > + * Report the available bandwidth at the device.  If this is less than the
> > + * device is capable of, report the device's maximum possible bandwidth and
> > + * the upstream link that limits its performance to less than that.
> > + */
> > +void pcie_print_link_status(struct pci_dev *dev)
> > +{
> > +   enum pcie_link_width width, width_cap;
> > +   enum pci_bus_speed speed, speed_cap;
> > +   struct pci_dev *limiting_dev = NULL;
> > +   u32 bw_avail, bw_cap;
> > +
> > +   bw_cap = pcie_bandwidth_capable(dev, _cap, _cap);
> > +   bw_avail = pcie_bandwidth_available(dev, _dev, ,
> > );
> > +
> > +   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) : "",
> > +bw_cap, PCIE_SPEED2STR(speed_cap), width_cap);
> > +}
> 
> Personally, I would make thic last one a pci_warn() to indicate it at a
> higher log level, but I'm  ok with the wording, and if consensus is that
> this should be at info, I'm ok with that.

Tal's original patch did have a pci_warn() here, and we went back and
forth a bit.  They get bug reports when a device doesn't perform as
expected, which argues for pci_warn().  But they also got feedback
saying warnings are a bit too much, which argues for pci_info() [1]

I don't have a really strong opinion either way.  I have a slight
preference for info because the user may not be able to do anything
about it (there may not be a faster slot available), and I think
distros are usually configured so a warning interrupts the smooth
graphical boot.

It looks like mlx4, fm10k, and ixgbe currently use warnings, while
bnx2x, bnxt_en, and cxgb4 use info.  It's a tie so far :)

[1] https://lkml.kernel.org/r/e47f3628-b56c-4d0a-f18b-5ffaf261c...@mellanox.com

Here's a proposal for printing the bandwidth as "x.xxx Gb/s":

commit ad370f38c1b5e9b8bb941eaed84ebb676c4bdaa4
Author: Tal Gilboa 
Date:   Fri Mar 30 08:56:47 2018 -0500

PCI: Add pcie_print_link_status() to log link speed and whether it's limited

Add pcie_print_link_status().  This logs the current settings of the link
(speed, width, and total available bandwidth).

If the device is capable of more bandwidth but is limited by a slower
upstream link, we include information about the link that limits the
device's performance.

The user may be able to move the device to a different slot for better
performance.

This provides a unified method for all

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

2018-04-02 Thread Keller, Jacob E 
> -Original Message-
> From: Bjorn Helgaas [mailto:helg...@kernel.org]
> Sent: Friday, March 30, 2018 2:05 PM
> To: Tal Gilboa 
> Cc: Tariq Toukan ; Keller, Jacob E
> ; Ariel Elior ; Ganesh
> Goudar ; Kirsher, Jeffrey T
> ; everest-linux...@cavium.com; intel-wired-
> l...@lists.osuosl.org; netdev@vger.kernel.org; linux-ker...@vger.kernel.org;
> linux-...@vger.kernel.org
> Subject: [PATCH v5 05/14] PCI: Add pcie_print_link_status() to log link speed 
> and
> whether it's limited
> 
> From: Tal Gilboa 
> 
> Add pcie_print_link_status().  This logs the current settings of the link
> (speed, width, and total available bandwidth).
> 
> If the device is capable of more bandwidth but is limited by a slower
> upstream link, we include information about the link that limits the
> device's performance.
> 
> The user may be able to move the device to a different slot for better
> performance.
> 
> This provides a unified method for all PCI devices to report status and
> issues, instead of each device reporting in a different way, using
> different code.
> 
> Signed-off-by: Tal Gilboa 
> [bhelgaas: changelog, reword log messages, print device capabilities when
> not limited]
> Signed-off-by: Bjorn Helgaas 
> ---
>  drivers/pci/pci.c   |   29 +
>  include/linux/pci.h |1 +
>  2 files changed, 30 insertions(+)
> 
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index e00d56b12747..cec7aed09f6b 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -5283,6 +5283,35 @@ u32 pcie_bandwidth_capable(struct pci_dev *dev,
> enum pci_bus_speed *speed,
>   return *width * PCIE_SPEED2MBS_ENC(*speed);
>  }
> 
> +/**
> + * pcie_print_link_status - Report the PCI device's link speed and width
> + * @dev: PCI device to query
> + *
> + * Report the available bandwidth at the device.  If this is less than the
> + * device is capable of, report the device's maximum possible bandwidth and
> + * the upstream link that limits its performance to less than that.
> + */
> +void pcie_print_link_status(struct pci_dev *dev)
> +{
> + enum pcie_link_width width, width_cap;
> + enum pci_bus_speed speed, speed_cap;
> + struct pci_dev *limiting_dev = NULL;
> + u32 bw_avail, bw_cap;
> +
> + bw_cap = pcie_bandwidth_capable(dev, _cap, _cap);
> + bw_avail = pcie_bandwidth_available(dev, _dev, ,
> );
> +
> + 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) : "",
> +  bw_cap, PCIE_SPEED2STR(speed_cap), width_cap);
> +}

Personally, I would make thic last one a pci_warn() to indicate it at a higher 
log level, but I'm  ok with the wording, and if consensus is that this should 
be at info, I'm ok with that.

Thanks,
Jake

> +EXPORT_SYMBOL(pcie_print_link_status);
> +
>  /**
>   * pci_select_bars - Make BAR mask from the type of resource
>   * @dev: the PCI device for which BAR mask is made
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index f2bf2b7a66c7..38f7957121ef 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -1086,6 +1086,7 @@ int pcie_get_minimum_link(struct pci_dev *dev, enum
> pci_bus_speed *speed,
>  u32 pcie_bandwidth_available(struct pci_dev *dev, struct pci_dev
> **limiting_dev,
>enum pci_bus_speed *speed,
>enum pcie_link_width *width);
> +void pcie_print_link_status(struct pci_dev *dev);
>  void pcie_flr(struct pci_dev *dev);
>  int __pci_reset_function_locked(struct pci_dev *dev);
>  int pci_reset_function(struct pci_dev *dev);