From 2f5d8e4ff947ad6673397083b48719cd6c59cd61 Mon Sep 17 00:00:00 2001 From: Yinghai Lu Date: Fri, 27 Jan 2012 10:55:11 -0800 Subject: [PATCH] PCI: pciehp: replace unconditional sleep with config space access check During reviewing | PCI: pciehp: wait 1000 ms before Link Training check Linus said: >... > That's a *long* time, and it's irritating to the user. It makes the > user think "the machine is slow". >... > And quite frankly, an unconditional one-second delay here seems bad. >Two seconds was unacceptable, one second is just bad. Try to access the pci conf of a pci device that is supposed to show up in 1s. If we can read back a valid vendor/device id, we can return early. Related discussion could be found: https://lkml.org/lkml/2011/12/6/339 -v2: seperate code to pci_bus_read_dev_vendor_id() from pci_scan_device() and reuse it from pciehp code. Suggested by Matthew Wilcox. -v3: According to Kenj, don't use array in stack, and don't wait too long for crs, also return fail status if not found. Also separate pci_bus_dev_read_vendor_id() change to another patch. Signed-off-by: Yinghai Lu Signed-off-by: Jesse Barnes --- drivers/pci/hotplug/pciehp_hpc.c | 49 ++++++++++++++++++++++---------- 1 file changed, 34 insertions(+), 15 deletions(-) diff --git a/drivers/pci/hotplug/pciehp_hpc.c b/drivers/pci/hotplug/pciehp_hpc.c index bcdbb164362..7dc9e33746a 100644 --- a/drivers/pci/hotplug/pciehp_hpc.c +++ b/drivers/pci/hotplug/pciehp_hpc.c @@ -265,10 +265,37 @@ static void pcie_wait_link_active(struct controller *ctrl) ctrl_dbg(ctrl, "Data Link Layer Link Active not set in 1000 msec\n"); } +static bool pci_bus_check_dev(struct pci_bus *bus, int devfn) +{ + u32 l; + int count = 0; + int delay = 1000, step = 20; + bool found = false; + + do { + found = pci_bus_read_dev_vendor_id(bus, devfn, &l, 0); + count++; + + if (found) + break; + + msleep(step); + delay -= step; + } while (delay > 0); + + if (count > 1 && pciehp_debug) + printk(KERN_DEBUG "pci %04x:%02x:%02x.%d id reading try %d times with interval %d ms to get %08x\n", + pci_domain_nr(bus), bus->number, PCI_SLOT(devfn), + PCI_FUNC(devfn), count, step, l); + + return found; +} + int pciehp_check_link_status(struct controller *ctrl) { u16 lnk_status; int retval = 0; + bool found = false; /* * Data Link Layer Link Active Reporting must be capable for @@ -280,13 +307,10 @@ int pciehp_check_link_status(struct controller *ctrl) else msleep(1000); - /* - * Need to wait for 1000 ms after Data Link Layer Link Active - * (DLLLA) bit reads 1b before sending configuration request. - * We need it before checking Link Training (LT) bit becuase - * LT is still set even after DLLLA bit is set on some platform. - */ - msleep(1000); + /* wait 100ms before read pci conf, and try in 1s */ + msleep(100); + found = pci_bus_check_dev(ctrl->pcie->port->subordinate, + PCI_DEVFN(0, 0)); retval = pciehp_readw(ctrl, PCI_EXP_LNKSTA, &lnk_status); if (retval) { @@ -302,16 +326,11 @@ int pciehp_check_link_status(struct controller *ctrl) return retval; } - /* - * If the port supports Link speeds greater than 5.0 GT/s, we - * must wait for 100 ms after Link training completes before - * sending configuration request. - */ - if (ctrl->pcie->port->subordinate->max_bus_speed > PCIE_SPEED_5_0GT) - msleep(100); - pcie_update_link_speed(ctrl->pcie->port->subordinate, lnk_status); + if (!found && !retval) + retval = -1; + return retval; } -- 2.20.1