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 Here's a proposal for printing the bandwidth as "x.xxx Gb/s": commit ad370f38c1b5e9b8bb941eaed84ebb676c4bdaa4 Author: Tal Gilboa <talgi@xxxxxxxxxxxx> 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 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, print bandwidth in Gb/s] Signed-off-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c index c6e3c0524699..ab2346041fa4 100644 --- a/drivers/pci/pci.c ++ b/drivers/pci/pci.c @@ -5287,6 +5287,38 @@ 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, "%u.%03u Gb/s available bandwidth (%s x%d link)\n", + bw_cap / 1000, bw_cap % 1000, + PCIE_SPEED2STR(speed_cap), width_cap); + else + pci_info(dev, "%u.%03u Gb/s available bandwidth, limited by %s x%d link at %s (capable of %u.%03u Gb/s with %s x%d link)\n", + bw_avail / 1000, bw_avail % 1000, + PCIE_SPEED2STR(speed), width, + limiting_dev ? pci_name(limiting_dev) : "<unknown>", + bw_cap / 1000, bw_cap % 1000, + PCIE_SPEED2STR(speed_cap), width_cap); +} +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);
