diff mbox series

[v2,2/4] PCI: Verify functions currently in D3cold have entered D0

Message ID 20240710205838.2413465-3-superm1@kernel.org
State New
Headers show
Series Verify devices transition from D3cold to D0 | expand

Commit Message

Mario Limonciello July 10, 2024, 8:58 p.m. UTC 
From: Mario Limonciello <mario.limonciello@amd.com>

It is reported that USB4 routers and downstream devices may behave
incorrectly if a dock cable is plugged in at approximately the time that
the autosuspend_delay is configured. In this situation the device has
attempted to enter D3cold, but didn't finish D3cold entry when the PCI
core tried to transition it back to D0.

Empirically measuring this situation an "aborted" D3cold exit takes
~60ms and a "normal" D3cold exit takes ~10ms.

The PCI-PM 1.2 spec specifies that the restore time for functions
in D3cold is either 'Full context restore or boot latency'.

As PCIe r6.0 sec 5.8 specifies that the device will have gone
through a conventional reset it may take some time for the
device to be ready.

Wait up to 1 sec as specified in PCIe r6.0 sec 6.6.1 for a device
in D3cold to return to D0.

Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
---
 drivers/pci/pci.c | 11 +++++++++++
 1 file changed, 11 insertions(+)
diff mbox series

Patch

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 4ad02ad640518..9af324ab6bb02 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -1388,6 +1388,17 @@  int pci_power_up(struct pci_dev *dev)
 	else if (state == PCI_D2)
 		udelay(PCI_PM_D2_DELAY);
 
+	/*
+	 * D3cold -> D0 will have gone through a conventional reset and may need
+	 * time to be ready.
+	 */
+	if (dev->current_state == PCI_D3cold) {
+		int ret;
+
+		ret = pci_dev_wait(dev, "D3cold->D0", PCI_RESET_WAIT);
+		if (ret)
+			return ret;
+	}
 end:
 	dev->current_state = PCI_D0;
 	if (need_restore)