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    Subject[PATCH 4.14 030/193] PCI/ASPM: Account for downstream devices Port Common_Mode_Restore_Time
    4.14-stable review patch.  If anyone has any objections, please let me know.


    From: Bjorn Helgaas <>

    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, 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 <>
    Reviewed-by: Vidya Sagar <>
    Acked-by: Rajat Jain <>
    Signed-off-by: Greg Kroah-Hartman <>

    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;

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