Messages in this thread |  | | Date | Sun, 21 Jul 2019 20:40:54 -0400 | From | Sasha Levin <> | Subject | Re: [PATCH AUTOSEL 4.14 086/105] PCI / ACPI: Use cached ACPI device state to get PCI device power state |
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On Tue, Jul 16, 2019 at 11:22:44AM +0200, Rafael J. Wysocki wrote: >On 7/15/2019 4:28 PM, Sasha Levin wrote: >>From: Mika Westerberg <mika.westerberg@linux.intel.com> >> >>[ Upstream commit 83a16e3f6d70da99896c7a2639c0b60fff13afb8 ] >> >>The ACPI power state returned by acpi_device_get_power() may depend on >>the configuration of ACPI power resources in the system which may change >>any time after acpi_device_get_power() has returned, unless the >>reference counters of the ACPI power resources in question are set to >>prevent that from happening. Thus it is invalid to use acpi_device_get_power() >>in acpi_pci_get_power_state() the way it is done now and the value of >>the ->power.state field in the corresponding struct acpi_device objects >>(which reflects the ACPI power resources reference counting, among other >>things) should be used instead. >> >>As an example where this becomes an issue is Intel Ice Lake where the >>Thunderbolt controller (NHI), two PCIe root ports (RP0 and RP1) and xHCI >>all share the same power resources. The following picture with power >>resources marked with [] shows the topology: >> >> Host bridge >> | >> +- RP0 ---\ >> +- RP1 ---|--+--> [TBT] >> +- NHI --/ | >> | | >> | v >> +- xHCI --> [D3C] >> >>Here TBT and D3C are the shared ACPI power resources. ACPI _PR3() method >>of the devices in question returns either TBT or D3C or both. >> >>Say we runtime suspend first the root ports RP0 and RP1, then NHI. Now >>since the TBT power resource is still on when the root ports are runtime >>suspended their dev->current_state is set to D3hot. When NHI is runtime >>suspended TBT is finally turned off but state of the root ports remain >>to be D3hot. Now when the xHCI is runtime suspended D3C gets also turned >>off. PCI core thus has power states of these devices cached in their >>dev->current_state as follows: >> >> RP0 -> D3hot >> RP1 -> D3hot >> NHI -> D3cold >> xHCI -> D3cold >> >>If the user now runs lspci for instance, the result is all 1's like in >>the below output (00:07.0 is the first root port, RP0): >> >>00:07.0 PCI bridge: Intel Corporation Device 8a1d (rev ff) (prog-if ff) >> !!! Unknown header type 7f >> Kernel driver in use: pcieport >> >>In short the hardware state is not in sync with the software state >>anymore. The exact same thing happens with the PME polling thread which >>ends up bringing the root ports back into D0 after they are runtime >>suspended. >> >>For this reason, modify acpi_pci_get_power_state() so that it uses the >>ACPI device power state that was cached by the ACPI core. This makes the >>PCI device power state match the ACPI device power state regardless of >>state of the shared power resources which may still be on at this point. >> >>Link: https://lore.kernel.org/r/20190618161858.77834-2-mika.westerberg@linux.intel.com >>Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com> >>Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> >>Signed-off-by: Sasha Levin <sashal@kernel.org> >>--- >> drivers/pci/pci-acpi.c | 3 ++- >> 1 file changed, 2 insertions(+), 1 deletion(-) >> >>diff --git a/drivers/pci/pci-acpi.c b/drivers/pci/pci-acpi.c >>index a3cedf8de863..688e195e85b4 100644 >>--- a/drivers/pci/pci-acpi.c >>+++ b/drivers/pci/pci-acpi.c >>@@ -563,7 +563,8 @@ static pci_power_t acpi_pci_get_power_state(struct pci_dev *dev) >> if (!adev || !acpi_device_power_manageable(adev)) >> return PCI_UNKNOWN; >>- if (acpi_device_get_power(adev, &state) || state == ACPI_STATE_UNKNOWN) >>+ state = adev->power.state; >>+ if (state == ACPI_STATE_UNKNOWN) >> return PCI_UNKNOWN; >> return state_conv[state]; > >This requires additional changes to really work in all cases, please >do not include it alone into -stable.
I've dropped it, thanks!
-- Thanks, Sasha
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