On Wed, May 06, 2020 at 01:34:21AM +0800, Kai-Heng Feng wrote:
> The TI PCIe-to-PCI bridge prevents the Intel SoC from entering power
> state deeper than PC3 due to disabled ASPM, consumes lots of unnecessary
> power. On Windows ASPM L1 is enabled on the device and its upstream
> bridge, so it can make the Intel SoC reach PC8 or PC10 to save lots of
> power.
>
> In short, ASPM always gets disabled on bridge-to-bridge link.
>
> The special case was part of first ASPM introduction patch, commit
> 7d715a6c1ae5 ("PCI: add PCI Express ASPM support"). However, it didn't
> explain why ASPM needs to be disabled in special bridge-to-bridge case.
>
> Let's remove the the special case, as PCIe spec already envisioned ASPM
> on bridge-to-bridge link.
>
> Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=207571
> Signed-off-by: Kai-Heng Feng <kai.heng.f...@canonical.com>
Applied to pci/aspm for v5.8, thanks!
I did keep your Reviewed-by, Mika. If the fact that this applies only
to the PCIe-to-PCI/PCI-X case makes your reviewed-by invalid, just let
me know and I'll drop it.
> ---
> v3:
> - Remove the special case completely.
>
> v2:
> - Enable ASPM on root complex <-> bridge <-> bridge, instead of using
> quirk.
> drivers/pci/pcie/aspm.c | 10 ----------
> 1 file changed, 10 deletions(-)
>
> diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
> index 2378ed692534..b17e5ffd31b1 100644
> --- a/drivers/pci/pcie/aspm.c
> +++ b/drivers/pci/pcie/aspm.c
> @@ -628,16 +628,6 @@ static void pcie_aspm_cap_init(struct pcie_link_state
> *link, int blacklist)
>
> /* Setup initial capable state. Will be updated later */
> link->aspm_capable = link->aspm_support;
> - /*
> - * If the downstream component has pci bridge function, don't
> - * do ASPM for now.
> - */
> - list_for_each_entry(child, &linkbus->devices, bus_list) {
> - if (pci_pcie_type(child) == PCI_EXP_TYPE_PCI_BRIDGE) {
> - link->aspm_disable = ASPM_STATE_ALL;
> - break;
> - }
> - }
>
> /* Get and check endpoint acceptable latencies */
> list_for_each_entry(child, &linkbus->devices, bus_list) {
> --
> 2.17.1
>
