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Subject[PATCH 4.4 026/135] PCI/ASPM: Allow ASPM on links to PCIe-to-PCI/PCI-X Bridges
Date
From: Kai-Heng Feng <kai.heng.feng@canonical.com>

[ Upstream commit 66ff14e59e8a30690755b08bc3042359703fb07a ]

7d715a6c1ae5 ("PCI: add PCI Express ASPM support") added the ability for
Linux to enable ASPM, but for some undocumented reason, it didn't enable
ASPM on links where the downstream component is a PCIe-to-PCI/PCI-X Bridge.

Remove this exclusion so we can enable ASPM on these links.

The Dell OptiPlex 7080 mentioned in the bugzilla has a TI XIO2001
PCIe-to-PCI Bridge. Enabling ASPM on the link leading to it allows the
Intel SoC to enter deeper Package C-states, which is a significant power
savings.

[bhelgaas: commit log]
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=207571
Link: https://lore.kernel.org/r/20200505173423.26968-1-kai.heng.feng@canonical.com
Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
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 c6a012b5ba390..966b6947e5656 100644
--- a/drivers/pci/pcie/aspm.c
+++ b/drivers/pci/pcie/aspm.c
@@ -388,16 +388,6 @@ 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) {
--
2.25.1
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