On 4/1/2022 07:29, Bjorn Helgaas wrote:
On Fri, Apr 01, 2022 at 01:44:42PM +0200, Rafael J. Wysocki wrote:
On Fri, Apr 1, 2022 at 5:40 AM Mario Limonciello
<mario.limonciello@xxxxxxx> wrote:
acpi_pci_bridge_d3(dev) returns "true" if "dev" is a hotplug bridge
that can handle hotplug events while in D3. Previously this meant:
1) "dev" has a _PS0 or _PR0 method, or
2) The Root Port above "dev" has a _DSD with a "HotPlugSupportInD3"
property with value 1.
This did not consider_S0W, which tells us the deepest D-state from
which a device can wake itself (ACPI v6.4, sec 7.3.20).
On some platforms, e.g., AMD Yellow Carp, firmware may supply
"HotPlugSupportInD3" even though the platform does not supply power
resources through _PRW and _S0W tells us the device cannot wake from
More importantly, it doesn't supply a wakeup GPE number through _PRW,
so from the ACPI perspective the bridge has no way of generating
wakeup signals.
Perfect, thanks. That's the missing piece about _PRW.
D3hot. With the previous code, these devices could be put in D3hot
and hotplugged devices would not be recognized without manually
rescanning.
If _S0W exists and says the Root Port cannot wake itself from D3hot,
return "false" to indicate that "dev" cannot handle hotplug events
while in D3.
1) "dev" has a _PS0 or _PR0 method, or
2a) The Root Port above "dev" has _PRW and
2b) If the Root Port above "dev" has _S0W, it can wake from D3hot or
D3cold and
2c) The Root Port above "dev" has a _DSD with a
"HotPlugSupportInD3" property with value 1.
Windows 10 and Windows 11 both will prevent the bridge from going in D3
when the firmware is configured this way and this change aligns the
handling of the situation to be the same.
Link: https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fuefi.org%2Fhtmlspecs%2FACPI_Spec_6_4_html%2F07_Power_and_Performance_Mgmt%2Fdevice-power-management-objects.html%3Fhighlight%3Ds0w%23s0w-s0-device-wake-state&data=04%7C01%7Cmario.limonciello%40amd.com%7Cc8ff8ac0568049a166bd08da13db41f3%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637844129686586061%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000&sdata=bjd5NnFaGslXcSVvShZMRHzuedEx8VgGnEnCGlWZ%2F2Q%3D&reserved=0
Link: https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fdocs.microsoft.com%2Fen-us%2Fwindows-hardware%2Fdrivers%2Fpci%2Fdsd-for-pcie-root-ports%23identifying-pcie-root-ports-supporting-hot-plug-in-d3&data=04%7C01%7Cmario.limonciello%40amd.com%7Cc8ff8ac0568049a166bd08da13db41f3%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637844129686586061%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000&sdata=r11UKOwL6SvGv4VCxaDyH0k15dsJib%2BJvRCS2MRobUQ%3D&reserved=0
Fixes: 26ad34d510a87 ("PCI / ACPI: Whitelist D3 for more PCIe hotplug ports")
Signed-off-by: Mario Limonciello <mario.limonciello@xxxxxxx>
--
v5->v6:
* Re-order checks to only check for _DSD if necessary as suggested by Bjorn.
* Adjust commit message wording
* Drop rewording comment patch, just apply it while moving text to avoid
ping-ponging the same lines in the commits.
v4-v5:
* Don't fail if _S0W is missing
---
drivers/pci/pci-acpi.c | 25 +++++++++++++++++++------
1 file changed, 19 insertions(+), 6 deletions(-)
diff --git a/drivers/pci/pci-acpi.c b/drivers/pci/pci-acpi.c
index 1f15ab7eabf8..5ab797e2709d 100644
--- a/drivers/pci/pci-acpi.c
+++ b/drivers/pci/pci-acpi.c
@@ -976,7 +976,9 @@ bool acpi_pci_bridge_d3(struct pci_dev *dev)
{
const union acpi_object *obj;
struct acpi_device *adev;
+ unsigned long long state;
struct pci_dev *rpdev;
+ acpi_status status;
if (acpi_pci_disabled || !dev->is_hotplug_bridge)
return false;
@@ -985,12 +987,6 @@ bool acpi_pci_bridge_d3(struct pci_dev *dev)
if (acpi_pci_power_manageable(dev))
return true;
- /*
- * The ACPI firmware will provide the device-specific properties through
- * _DSD configuration object. Look for the 'HotPlugSupportInD3' property
- * for the root port and if it is set we know the hierarchy behind it
- * supports D3 just fine.
- */
rpdev = pcie_find_root_port(dev);
if (!rpdev)
return false;
@@ -999,6 +995,23 @@ bool acpi_pci_bridge_d3(struct pci_dev *dev)
if (!adev)
return false;
+ /*
+ * If the bridge can't wake from D3hot, it can't signal hotplug
+ * events in D3hot.
I would say "If the bridge cannot signal wakeup signals at all, it
cannot signal hotplug events from low-power states including D3hot and
D3cold."
With the two above remarks addressed, please feel free to add
Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
Great, thanks!
Bjorn,
Please let me know if you want me to send up a v7 with the minor remark
updates, or if you can just fix those up while committing.
Thanks!
+ */
+ if (!adev->wakeup.flags.valid)
+ return false;
+
+ status = acpi_evaluate_integer(adev->handle, "_S0W", NULL, &state);
+ if (ACPI_SUCCESS(status) && state < ACPI_STATE_D3_HOT)
+ return false;
+
+ /*
+ * The ACPI firmware will provide the device-specific properties through
+ * _DSD configuration object. Look for the 'HotPlugSupportInD3' property
+ * for the root port and if it is set we make an assumption that the
+ * hierarchy behind it supports D3 as well.
+ */
if (acpi_dev_get_property(adev, "HotPlugSupportInD3",
ACPI_TYPE_INTEGER, &obj) < 0)
return false;
--
2.34.1
