On Apollolake platforms, PCIe rootport takes a long time to resume
from S3. With 100ms delay before read pci conf, rootport takes
~200ms during resume.
commit 2f5d8e4ff947 ("PCI: pciehp: replace unconditional sleep with
config space access check") is the one that added the 100ms delay
before reading pci conf.
This patch includes a condition check for 100ms dealy before reading
PCIe conf. This delay in included only when PCIe
max_bus_speed > 5.0 GT/s. Root port takes ~16ms during resume.
With 100ms delay:
[ 155.102713] calling 0000:00:14.0+ @ 70, parent: pci0000:00, cb: pci_pm_resume_noirq
[ 155.119337] call 0000:00:14.0+ returned 0 after 16231 usecs
[ 155.119467] calling 0000:01:00.0+ @ 5845, parent: 0000:00:14.0, cb: pci_pm_resume_noirq
[ 155.321670] call 0000:00:14.0+ returned 0 after 185327 usecs
[ 155.321743] calling 0000:01:00.0+ @ 5849, parent: 0000:00:14.0, cb: pci_pm_resume
With Condition check:
[ 36.624709] calling 0000:00:14.0+ @ 4434, parent: pci0000:00, cb: pci_pm_resume_noirq
[ 36.641367] call 0000:00:14.0+ returned 0 after 16263 usecs
[ 36.652458] calling 0000:00:14.0+ @ 4443, parent: pci0000:00, cb: pci_pm_resume
[ 36.652673] call 0000:00:14.0+ returned 0 after 208 usecs
[ 36.652863] calling 0000:01:00.0+ @ 4442, parent: 0000:00:14.0, cb: pci_pm_resume
Signed-off-by: Vaibhav Shankar <vaibhav.shankar@xxxxxxxxx>
---
changes in v2:
- Modify patch description.
- Add condition check for 100ms delay before read pci conf as
suggested by Yinghai.
drivers/pci/hotplug/pciehp_hpc.c | 11 +++++++++--
1 file changed, 9 insertions(+), 2 deletions(-)
diff --git a/drivers/pci/hotplug/pciehp_hpc.c b/drivers/pci/hotplug/pciehp_hpc.c
index b57fc6d..2b10e5f 100644
--- a/drivers/pci/hotplug/pciehp_hpc.c
+++ b/drivers/pci/hotplug/pciehp_hpc.c
@@ -311,8 +311,15 @@ int pciehp_check_link_status(struct controller *ctrl)
else
msleep(1000);
- /* wait 100ms before read pci conf, and try in 1s */
- msleep(100);
+ /*
+ * 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);
+
+ /* try in 1s */
found = pci_bus_check_dev(ctrl->pcie->port->subordinate,
PCI_DEVFN(0, 0));
--
1.7.9.5
--
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