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| author | Tal Gilboa <talgi@mellanox.com> | 2018-03-30 16:32:03 +0300 |
|---|---|---|
| committer | Bjorn Helgaas <bhelgaas@google.com> | 2018-03-30 23:33:38 +0300 |
| commit | b852f63aa6cee3f4846383377c414ae9c4fbc166 (patch) | |
| tree | 55fd810d9b5c8b029cf63bc4e70ee4990275b66a | |
| parent | c70b65fb7f121da7d01f62588ce6abb4741f513f (diff) | |
| download | linux-b852f63aa6cee3f4846383377c414ae9c4fbc166.tar.xz | |
PCI: Add pcie_bandwidth_capable() to compute max supported link bandwidth
Add pcie_bandwidth_capable() to compute the max link bandwidth supported by
a device, based on the max link speed and width, adjusted by the encoding
overhead.
The maximum bandwidth of the link is computed as:
max_link_width * max_link_speed * (1 - encoding_overhead)
2.5 and 5.0 GT/s links use 8b/10b encoding, which reduces the raw bandwidth
available by 20%; 8.0 GT/s and faster links use 128b/130b encoding, which
reduces it by about 1.5%.
The result is in Mb/s, i.e., megabits/second, of raw bandwidth.
Signed-off-by: Tal Gilboa <talgi@mellanox.com>
[bhelgaas: add 16 GT/s, adjust for pcie_get_speed_cap() and
pcie_get_width_cap() signatures, don't export outside drivers/pci]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
| -rw-r--r-- | drivers/pci/pci.c | 22 | ||||
| -rw-r--r-- | drivers/pci/pci.h | 10 |
2 files changed, 32 insertions, 0 deletions
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c index 43075be79388..ff1e72060952 100644 --- a/drivers/pci/pci.c +++ b/drivers/pci/pci.c @@ -5209,6 +5209,28 @@ enum pcie_link_width pcie_get_width_cap(struct pci_dev *dev) } /** + * pcie_bandwidth_capable - calculate a PCI device's link bandwidth capability + * @dev: PCI device + * @speed: storage for link speed + * @width: storage for link width + * + * Calculate a PCI device's link bandwidth by querying for its link speed + * and width, multiplying them, and applying encoding overhead. The result + * is in Mb/s, i.e., megabits/second of raw bandwidth. + */ +u32 pcie_bandwidth_capable(struct pci_dev *dev, enum pci_bus_speed *speed, + enum pcie_link_width *width) +{ + *speed = pcie_get_speed_cap(dev); + *width = pcie_get_width_cap(dev); + + if (*speed == PCI_SPEED_UNKNOWN || *width == PCIE_LNK_WIDTH_UNKNOWN) + return 0; + + return *width * PCIE_SPEED2MBS_ENC(*speed); +} + +/** * pci_select_bars - Make BAR mask from the type of resource * @dev: the PCI device for which BAR mask is made * @flags: resource type mask to be selected diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h index 66738f1050c0..ce9adec6c66e 100644 --- a/drivers/pci/pci.h +++ b/drivers/pci/pci.h @@ -261,8 +261,18 @@ void pci_disable_bridge_window(struct pci_dev *dev); (speed) == PCIE_SPEED_2_5GT ? "2.5 GT/s" : \ "Unknown speed") +/* PCIe speed to Mb/s reduced by encoding overhead */ +#define PCIE_SPEED2MBS_ENC(speed) \ + ((speed) == PCIE_SPEED_16_0GT ? 16000*128/130 : \ + (speed) == PCIE_SPEED_8_0GT ? 8000*128/130 : \ + (speed) == PCIE_SPEED_5_0GT ? 5000*8/10 : \ + (speed) == PCIE_SPEED_2_5GT ? 2500*8/10 : \ + 0) + enum pci_bus_speed pcie_get_speed_cap(struct pci_dev *dev); enum pcie_link_width pcie_get_width_cap(struct pci_dev *dev); +u32 pcie_bandwidth_capable(struct pci_dev *dev, enum pci_bus_speed *speed, + enum pcie_link_width *width); /* Single Root I/O Virtualization */ struct pci_sriov { |