linux-kernel - [PATCH v3 3/5] PCI: Verify functions currently in D3cold have entered D0

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Message-ID: <20240712181246.811044-4-superm1@kernel.org>
Date: Fri, 12 Jul 2024 13:12:44 -0500
From: superm1@...nel.org
To: Bjorn Helgaas <bhelgaas@...gle.com>,
	Mathias Nyman <mathias.nyman@...el.com>,
	Mika Westerberg <mika.westerberg@...ux.intel.com>
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>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Mario Limonciello <mario.limonciello@....com>,
	Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
Subject: [PATCH v3 3/5] PCI: Verify functions currently in D3cold have entered D0

From: Mario Limonciello <mario.limonciello@....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 ~6ms.

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.

Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
Signed-off-by: Mario Limonciello <mario.limonciello@....com>
---
 drivers/pci/pci.c | 11 +++++++++++
 drivers/pci/pci.h |  1 +
 2 files changed, 12 insertions(+)

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 658a139f74ab0..14dab7bc64ba4 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -1396,6 +1396,17 @@ 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, PCI_DEV_WAIT_D3COLD_D0, PCI_RESET_WAIT);
+		if (ret)
+			return ret;
+	}
 end:
 	dev->current_state = PCI_D0;
 	if (need_restore)
diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
index 88f54d22118dc..9482539b9830a 100644
--- a/drivers/pci/pci.h
+++ b/drivers/pci/pci.h
@@ -11,6 +11,7 @@ enum pci_reset_type {
 	PCI_DEV_WAIT_BUS_RESET,
 	PCI_DEV_WAIT_RESUME,
 	PCI_DEV_WAIT_DPC,
+	PCI_DEV_WAIT_D3COLD_D0,
 };
 
 /* Number of possible devfns: 0.0 to 1f.7 inclusive */
-- 
2.43.0