On 4/2/2018 11:25 PM, Keller, Jacob E wrote:
-----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 speedandwhether 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@xxxxxxxxxxxxWith 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.
