> -----Original Message----- > From: netdev-owner@xxxxxxxxxxxxxxx [mailto:netdev-owner@xxxxxxxxxxxxxxx] > On Behalf Of Bjorn Helgaas > Sent: Monday, April 02, 2018 1:32 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 12/14] fm10k: Report PCIe link properties with > pcie_print_link_status() > > On Mon, Apr 02, 2018 at 03:56:06PM +0000, Keller, Jacob E wrote: > > > -----Original Message----- > > > From: Bjorn Helgaas [mailto:helgaas@xxxxxxxxxx] > > > Sent: Friday, March 30, 2018 2:06 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 12/14] fm10k: Report PCIe link properties with > > > pcie_print_link_status() > > > > > > From: Bjorn Helgaas <bhelgaas@xxxxxxxxxx> > > > > > > Use pcie_print_link_status() to report PCIe link speed and possible > > > limitations instead of implementing this in the driver itself. > > > > > > Note that pcie_get_minimum_link() can return misleading information > because > > > it finds the slowest link and the narrowest link without considering the > > > total bandwidth of the link. If the path contains a 16 GT/s x1 link and a > > > 2.5 GT/s x16 link, pcie_get_minimum_link() returns 2.5 GT/s x1, which > > > corresponds to 250 MB/s of bandwidth, not the actual available bandwidth of > > > about 2000 MB/s for a 16 GT/s x1 link. > > > > This comment is about what's being fixed, so it would have been easier to > > parse if it were written to more clearly indicate that we're removing > > (and not adding) this behavior. > > Good point. Is this any better? > > fm10k: Report PCIe link properties with pcie_print_link_status() > > Previously the driver used pcie_get_minimum_link() to warn when the NIC > is in a slot that can't supply as much bandwidth as the NIC could use. > > pcie_get_minimum_link() can be misleading because it finds the slowest link > and the narrowest link (which may be different links) without considering > the total bandwidth of each link. For a path with a 16 GT/s x1 link and a > 2.5 GT/s x16 link, it returns 2.5 GT/s x1, which corresponds to 250 MB/s of > bandwidth, not the true available bandwidth of about 1969 MB/s for a > 16 GT/s x1 link. > > Use pcie_print_link_status() to report PCIe link speed and possible > limitations instead of implementing this in the driver itself. This finds > the slowest link in the path to the device by computing the total bandwidth > of each link and compares that with the capabilities of the device. > > Note that the driver previously used dev_warn() to suggest using a > different slot, but pcie_print_link_status() uses dev_info() because if the > platform has no faster slot available, the user can't do anything about the > warning and may not want to be bothered with it. Perfect! Thanks! -Jake
