> -----Original Message----- > From: Bjorn Helgaas [mailto:helgaas@xxxxxxxxxx] > Sent: Monday, April 02, 2018 12:58 PM > To: Keller, Jacob E <jacob.e.keller@xxxxxxxxx> > Cc: Tal Gilboa <talgi@xxxxxxxxxxxx>; Tariq Toukan <tariqt@xxxxxxxxxxxx>; Ariel > Elior <ariel.elior@xxxxxxxxxx>; Ganesh Goudar <ganeshgr@xxxxxxxxxxx>; > Kirsher, Jeffrey T <jeffrey.t.kirsher@xxxxxxxxx>; everest-linux-l2@xxxxxxxxxx; > intel-wired-lan@xxxxxxxxxxxxxxxx; netdev@xxxxxxxxxxxxxxx; linux- > kernel@xxxxxxxxxxxxxxx; linux-pci@xxxxxxxxxxxxxxx > 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 +0000, Keller, Jacob E wrote: > > > -----Original Message----- > > > From: Bjorn Helgaas [mailto:helgaas@xxxxxxxxxx] > > > Sent: Friday, March 30, 2018 2:05 PM > > > To: Tal Gilboa <talgi@xxxxxxxxxxxx> > > > Cc: Tariq Toukan <tariqt@xxxxxxxxxxxx>; Keller, Jacob E > > > <jacob.e.keller@xxxxxxxxx>; Ariel Elior <ariel.elior@xxxxxxxxxx>; Ganesh > > > Goudar <ganeshgr@xxxxxxxxxxx>; Kirsher, Jeffrey T > > > <jeffrey.t.kirsher@xxxxxxxxx>; everest-linux-l2@xxxxxxxxxx; intel-wired- > > > lan@xxxxxxxxxxxxxxxx; netdev@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; > > > linux-pci@xxxxxxxxxxxxxxx > > > Subject: [PATCH v5 05/14] PCI: Add pcie_print_link_status() to log link speed > and > > > whether it's limited > > > > > > From: Tal Gilboa <talgi@xxxxxxxxxxxx> > > > > > > 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 <talgi@xxxxxxxxxxxx> > > > [bhelgaas: changelog, reword log messages, print device capabilities when > > > not limited] > > > Signed-off-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx> > > > --- > > > 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, &speed_cap, &width_cap); > > > + bw_avail = pcie_bandwidth_available(dev, &limiting_dev, &speed, > > > &width); > > > + > > > + 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); > > > +} > > > > 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- > 5ffaf261ccc0@xxxxxxxxxxxx > 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
