linux-kernel - [PATCH 2/4] PCI: Verify functions currently in D3cold have entered D0

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Message-ID: <20240613054204.5850-3-mario.limonciello@amd.com>
Date: Thu, 13 Jun 2024 00:42:02 -0500
From: Mario Limonciello <mario.limonciello@....com>
To: Bjorn Helgaas <bhelgaas@...gle.com>, Mathias Nyman
	<mathias.nyman@...el.com>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>
CC: "open list:PCI SUBSYSTEM" <linux-pci@...r.kernel.org>, open list
	<linux-kernel@...r.kernel.org>, "open list:USB XHCI DRIVER"
	<linux-usb@...r.kernel.org>, Daniel Drake <drake@...lessos.org>, Gary Li
	<Gary.Li@....com>, Mika Westerberg <mika.westerberg@...ux.intel.com>, "Mario
 Limonciello" <mario.limonciello@....com>
Subject: [PATCH 2/4] PCI: Verify functions currently in D3cold have entered D0

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@....com>
---
 drivers/pci/pci.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 41961e28a86c..a6ed85dd8d92 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -1387,6 +1387,17 @@ 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)
-- 
2.43.0