diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c index 7cb29a223b73a0b9947009e47a1427781f9c7c18..827a9f99a8e5f088ed0aa8c8c06d5d872a57832b 100644 --- a/drivers/pci/pci.c +++ b/drivers/pci/pci.c @@ -3820,27 +3820,49 @@ int pci_wait_for_pending_transaction(struct pci_dev *dev) } EXPORT_SYMBOL(pci_wait_for_pending_transaction); -/* - * We should only need to wait 100ms after FLR, but some devices take longer. - * Wait for up to 1000ms for config space to return something other than -1. - * Intel IGD requires this when an LCD panel is attached. We read the 2nd - * dword because VFs don't implement the 1st dword. - */ static void pci_flr_wait(struct pci_dev *dev) { - int i = 0; + int delay = 1, timeout = 60000; u32 id; - do { - msleep(100); + /* + * Per PCIe r3.1, sec 6.6.2, a device must complete an FLR within + * 100ms, but may silently discard requests while the FLR is in + * progress. Wait 100ms before trying to access the device. + */ + msleep(100); + + /* + * After 100ms, the device should not silently discard config + * requests, but it may still indicate that it needs more time by + * responding to them with CRS completions. The Root Port will + * generally synthesize ~0 data to complete the read (except when + * CRS SV is enabled and the read was for the Vendor ID; in that + * case it synthesizes 0x0001 data). + * + * Wait for the device to return a non-CRS completion. Read the + * Command register instead of Vendor ID so we don't have to + * contend with the CRS SV value. + */ + pci_read_config_dword(dev, PCI_COMMAND, &id); + while (id == ~0) { + if (delay > timeout) { + dev_warn(&dev->dev, "not ready %dms after FLR; giving up\n", + 100 + delay - 1); + return; + } + + if (delay > 1000) + dev_info(&dev->dev, "not ready %dms after FLR; waiting\n", + 100 + delay - 1); + + msleep(delay); + delay *= 2; pci_read_config_dword(dev, PCI_COMMAND, &id); - } while (i++ < 10 && id == ~0); + } - if (id == ~0) - dev_warn(&dev->dev, "Failed to return from FLR\n"); - else if (i > 1) - dev_info(&dev->dev, "Required additional %dms to return from FLR\n", - (i - 1) * 100); + if (delay > 1000) + dev_info(&dev->dev, "ready %dms after FLR\n", 100 + delay - 1); } /**