On 8/29/2024 19:01, Bjorn Helgaas wrote:
On Fri, Aug 23, 2024 at 10:40:20AM -0500, Mario Limonciello wrote:
From: Mario Limonciello <mario.limonciello@xxxxxxx>
If a dock is plugged in at the same time as autosuspend delay then
this can cause malfunctions in the USB4 stack. This happens because
the device is still in D3cold at the time that the PCI core handed
control back to the USB4 stack.
A device that has gone through a reset may return a value in
PCI_COMMAND but that doesn't mean it's finished transitioning to D0.
For devices that support power management explicitly check
PCI_PM_CTRL on everything but system resume to ensure the transition
happened.
Still trying to understand what's going on here.
I posted a change to pci_dev_wait() to read Vendor ID, look for Config
RRS status, and wait for a successful completion (when RRS Software
Visibility is enabled) [1].
You tested that and found that it didn't help with *this* issue [2].
I assume you tested something like v6.11-rc plus the patches from [1],
i.e., without the PCI_PM_CTRL changes in this series.
1) Initially the device is in D0
2) We put it in D3cold (using some ACPI method) because the
autosuspend delay expired (?)
3) Plugging in the dock wakes up the device, so we power up the
device (via pci_power_up(), which again uses some ACPI method), and
it should transition to D0uninitialized
4) The USB4 stack sees the device but thinks it's in D3cold (?)
If your testing only included [1], but did not include the
pci_power_up() change from patch 3/5 "Verify functions currently in
D3cold have entered D0", I don't think we would call pci_dev_wait(),
so I wouldn't expect [1] to make any difference.
If you *did* include both [1] and patch 3/5, the implication would be
that pci_dev_wait() successfully read the Vendor ID, meaning the
device is not in D3cold when pci_power_up() returns.
The testing here was from the LTS 6.6.y kernel with both [1] and patch
3/5 from this series.
I can get testing from 6.11-rc6 with a combination of patches if you
would like.
Can you clarify what you see and possibly expand/correct my timeline
above?
The timeline you shared is nearly correct. The USB4 stack *thinks* the
device is in D0 because of the return of pci_power_up().
As by polling PCI_PM_CTRL we can see it's still in D3, so it hasn't made
it to D0uninitialized yet.
I guess I reading between the lines you have an assumption that you
can't read the vendor ID from D3; which doesn't appear to be the case
from our testing.
[1] https://lore.kernel.org/linux-pci/20240827234848.4429-1-helgaas@xxxxxxxxxx/
[2] https://lore.kernel.org/linux-pci/30d9589a-8050-421b-a9a5-ad3422feadad@xxxxxxx/
Devices that don't support power management and system resume will
continue to use PCI_COMMAND.
Signed-off-by: Mario Limonciello <mario.limonciello@xxxxxxx>
---
v4->v5:
* Fix misleading indentation
* Amend commit message
---
drivers/pci/pci.c | 28 ++++++++++++++++++++--------
1 file changed, 20 insertions(+), 8 deletions(-)
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 1e219057a5069..f032a4aaec268 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -1309,21 +1309,33 @@ static int pci_dev_wait(struct pci_dev *dev, enum pci_reset_type reset_type, int
* the read (except when CRS SV is enabled and the read was for the
* Vendor ID; in that case it synthesizes 0x0001 data).
*
- * Wait for the device to return a non-CRS completion. Read the
- * Command register instead of Vendor ID so we don't have to
- * contend with the CRS SV value.
+ * Wait for the device to return a non-CRS completion. On devices
+ * that support PM control and on waits that aren't part of system
+ * resume read the PM control register to ensure the device has
+ * transitioned to D0. On devices that don't support PM control,
+ * or during system resume read the command register to instead of
+ * Vendor ID so we don't have to contend with the CRS SV value.
*/
for (;;) {
- u32 id;
-
if (pci_dev_is_disconnected(dev)) {
pci_dbg(dev, "disconnected; not waiting\n");
return -ENOTTY;
}
- pci_read_config_dword(dev, PCI_COMMAND, &id);
- if (!PCI_POSSIBLE_ERROR(id))
- break;
+ if (dev->pm_cap && reset_type != PCI_DEV_WAIT_RESUME) {
+ u16 pmcsr;
+
+ pci_read_config_word(dev, dev->pm_cap + PCI_PM_CTRL, &pmcsr);
+ if (!PCI_POSSIBLE_ERROR(pmcsr) &&
+ (pmcsr & PCI_PM_CTRL_STATE_MASK) == PCI_D0)
+ break;
+ } else {
+ u32 id;
+
+ pci_read_config_dword(dev, PCI_COMMAND, &id);
+ if (!PCI_POSSIBLE_ERROR(id))
+ break;
+ }
if (delay > timeout) {
pci_warn(dev, "not ready %dms after %s; giving up\n",
--
2.43.0
