4.14-stable review patch. If anyone has any objections, please let me know.
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From: Bjorn Helgaas bhelgaas@google.com
commit 94ac327e043ee40d7fc57b54541da50507ef4e99 upstream.
Every Port that supports the L1.2 substate advertises its Port Common_Mode_Restore_Time, i.e., the time the Port requires to re-establish common mode when exiting L1.2 (see PCIe r3.1, sec 7.33.2).
Per sec 5.5.3.3.1, when exiting L1.2, the Downstream Port (the device at the upstream end of the link) must send TS1 training sequences for at least T(COMMONMODE) after it detects electrical idle exit on the Link. We want this to be long enough for both ends of the Link, so we should set it to the maximum of the Port Common_Mode_Restore_Time for the upstream and downstream components on the Link.
Previously we only looked at the Port Common_Mode_Restore_Time of the upstream device, so if the downstream device required more time, we didn't program the upstream device's T(COMMONMODE) correctly.
Fixes: f1f0366dd6be ("PCI/ASPM: Calculate and save the L1.2 timing parameters") Signed-off-by: Bjorn Helgaas bhelgaas@google.com Reviewed-by: Vidya Sagar vidyas@nvidia.com Acked-by: Rajat Jain rajatja@google.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- drivers/pci/pcie/aspm.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/drivers/pci/pcie/aspm.c +++ b/drivers/pci/pcie/aspm.c @@ -453,7 +453,7 @@ static void aspm_calc_l1ss_info(struct p
/* Choose the greater of the two T_cmn_mode_rstr_time */ val1 = (upreg->l1ss_cap >> 8) & 0xFF; - val2 = (upreg->l1ss_cap >> 8) & 0xFF; + val2 = (dwreg->l1ss_cap >> 8) & 0xFF; if (val1 > val2) link->l1ss.ctl1 |= val1 << 8; else