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authorYinghai Lu <yinghai@kernel.org>2012-01-27 10:55:11 -0800
committerJesse Barnes <jbarnes@virtuousgeek.org>2012-02-14 08:45:00 -0800
commit2f5d8e4ff947ad6673397083b48719cd6c59cd61 (patch)
tree46e1c6901937b7f983b511d6e14498000e2989bb
parentefdc87dab1cdf25ba631181ac0ead3fb2023dd10 (diff)
downloadop-kernel-dev-2f5d8e4ff947ad6673397083b48719cd6c59cd61.zip
op-kernel-dev-2f5d8e4ff947ad6673397083b48719cd6c59cd61.tar.gz
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 <yinghai@kernel.org> Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
-rw-r--r--drivers/pci/hotplug/pciehp_hpc.c49
1 files changed, 34 insertions, 15 deletions
diff --git a/drivers/pci/hotplug/pciehp_hpc.c b/drivers/pci/hotplug/pciehp_hpc.c
index bcdbb16..7dc9e33 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;
}
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