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Date: Tue, 5 May 2020 20:27:59 +0800 From: Kai-Heng Feng <kai.heng.feng@...onical.com> To: bhelgaas@...gle.com Cc: Kai-Heng Feng <kai.heng.feng@...onical.com>, Heiner Kallweit <hkallweit1@...il.com>, "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>, "David S. Miller" <davem@...emloft.net>, Krzysztof Wilczynski <kw@...ux.com>, linux-pci@...r.kernel.org (open list:PCI SUBSYSTEM), linux-kernel@...r.kernel.org (open list) Subject: [PATCH v2] PCI/ASPM: Enable ASPM for root complex <-> bridge <-> bridge case 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. Currently, ASPM is disabled if downstream has bridge function. It was introduced by commit 7d715a6c1ae5 ("PCI: add PCI Express ASPM support"). The commit introduced PCIe ASPM support, but didn't explain why ASPM needs to be in that case. So relax the condition a bit to let bridge which connects to root complex enables ASPM, instead of removing it completely, to avoid regression. Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=207571 Signed-off-by: Kai-Heng Feng <kai.heng.feng@...onical.com> --- drivers/pci/pcie/aspm.c | 14 ++++++++------ 1 file changed, 8 insertions(+), 6 deletions(-) diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c index 2378ed692534..af5e22d78101 100644 --- a/drivers/pci/pcie/aspm.c +++ b/drivers/pci/pcie/aspm.c @@ -629,13 +629,15 @@ 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. + * If upstream bridge isn't connected to root complex and 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; + if (parent->bus->parent) { + 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; + } } } -- 2.17.1
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