From 4d07a05397c8c15c37c8c3abb7afaea1dcd2f0e7 Mon Sep 17 00:00:00 2001 From: Dave Jiang Date: Thu, 21 Dec 2023 15:03:39 -0700 Subject: cxl: Calculate and store PCI link latency for the downstream ports The latency is calculated by dividing the flit size over the bandwidth. Add support to retrieve the flit size for the CXL switch device and calculate the latency of the PCIe link. Cache the latency number with cxl_dport. Reviewed-by: Jonathan Cameron Signed-off-by: Dave Jiang Link: https://lore.kernel.org/r/170319621931.2212653.6800240203604822886.stgit@djiang5-mobl3 Signed-off-by: Dan Williams --- drivers/pci/pci.c | 38 ++++++++++++++++++++++++++++++++++++-- 1 file changed, 36 insertions(+), 2 deletions(-) (limited to 'drivers/pci') diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c index 55bc3576a985..00817d403ad4 100644 --- a/drivers/pci/pci.c +++ b/drivers/pci/pci.c @@ -6224,6 +6224,41 @@ int pcie_set_mps(struct pci_dev *dev, int mps) } EXPORT_SYMBOL(pcie_set_mps); +static enum pci_bus_speed to_pcie_link_speed(u16 lnksta) +{ + return pcie_link_speed[FIELD_GET(PCI_EXP_LNKSTA_CLS, lnksta)]; +} + +int pcie_link_speed_mbps(struct pci_dev *pdev) +{ + u16 lnksta; + int err; + + err = pcie_capability_read_word(pdev, PCI_EXP_LNKSTA, &lnksta); + if (err) + return err; + + switch (to_pcie_link_speed(lnksta)) { + case PCIE_SPEED_2_5GT: + return 2500; + case PCIE_SPEED_5_0GT: + return 5000; + case PCIE_SPEED_8_0GT: + return 8000; + case PCIE_SPEED_16_0GT: + return 16000; + case PCIE_SPEED_32_0GT: + return 32000; + case PCIE_SPEED_64_0GT: + return 64000; + default: + break; + } + + return -EINVAL; +} +EXPORT_SYMBOL(pcie_link_speed_mbps); + /** * pcie_bandwidth_available - determine minimum link settings of a PCIe * device and its bandwidth limitation @@ -6257,8 +6292,7 @@ u32 pcie_bandwidth_available(struct pci_dev *dev, struct pci_dev **limiting_dev, while (dev) { pcie_capability_read_word(dev, PCI_EXP_LNKSTA, &lnksta); - next_speed = pcie_link_speed[FIELD_GET(PCI_EXP_LNKSTA_CLS, - lnksta)]; + next_speed = to_pcie_link_speed(lnksta); next_width = FIELD_GET(PCI_EXP_LNKSTA_NLW, lnksta); next_bw = next_width * PCIE_SPEED2MBS_ENC(next_speed); -- cgit