linux-kernel - [PATCH 1/4] PCI: Check PCI_PM_CTRL in pci_dev

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Message-ID: <20240613054204.5850-2-mario.limonciello@amd.com>
Date: Thu, 13 Jun 2024 00:42:01 -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 1/4] PCI: Check PCI_PM_CTRL in pci_dev_wait()

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.  On devices that
support power management explicitly check PCI_PM_CTRL to ensure the
transition happened.  Devicees that don't support power management will
continue to use PCI_COMMAND.

Signed-off-by: Mario Limonciello <mario.limonciello@....com>
---
 drivers/pci/pci.c | 26 +++++++++++++++++++-------
 1 file changed, 19 insertions(+), 7 deletions(-)

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 59e0949fb079..41961e28a86c 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -1270,21 +1270,33 @@ static int pci_dev_wait(struct pci_dev *dev, char *reset_type, int timeout)
 	 * 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 read the PM control register to ensure
+	 * the device has transitioned to D0.  On devices that don't support
+	 * PM control, 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) {
+			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