linux-kernel - [PATCH 5.15 528/846] thunderbolt: Runtime PM activate both ends of the device link

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Message-Id: <20220124184119.221967598@linuxfoundation.org>
Date:   Mon, 24 Jan 2022 19:40:45 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.15 528/846] thunderbolt: Runtime PM activate both ends of the device link

From: Mika Westerberg <mika.westerberg@...ux.intel.com>

[ Upstream commit f3380cac0c0b3a6f49ab161e2a057c363962f48d ]

If protocol tunnels are already up when the driver is loaded, for
instance if the boot firmware implements connection manager of its own,
runtime PM reference count of the consumer devices behind the tunnel
might have been increased already before the device link is created but
the supplier device runtime PM reference count is not. This leads to a
situation where the supplier (the Thunderbolt driver) can runtime
suspend even if it should not because the corresponding protocol tunnel
needs to be up causing the devices to be removed from the corresponding
native bus.

Prevent this from happening by making both sides of the link runtime PM
active briefly. The pm_runtime_put() for the consumer (PCIe
root/downstream port, xHCI) then allows it to runtime suspend again but
keeps the supplier runtime resumed the whole time it is runtime active.

Signed-off-by: Mika Westerberg <mika.westerberg@...ux.intel.com>
Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/thunderbolt/acpi.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/drivers/thunderbolt/acpi.c b/drivers/thunderbolt/acpi.c
index b67e72d5644b3..7c9597a339295 100644
--- a/drivers/thunderbolt/acpi.c
+++ b/drivers/thunderbolt/acpi.c
@@ -7,6 +7,7 @@
  */
 
 #include <linux/acpi.h>
+#include <linux/pm_runtime.h>
 
 #include "tb.h"
 
@@ -74,8 +75,18 @@ static acpi_status tb_acpi_add_link(acpi_handle handle, u32 level, void *data,
 		 pci_pcie_type(pdev) == PCI_EXP_TYPE_DOWNSTREAM))) {
 		const struct device_link *link;
 
+		/*
+		 * Make them both active first to make sure the NHI does
+		 * not runtime suspend before the consumer. The
+		 * pm_runtime_put() below then allows the consumer to
+		 * runtime suspend again (which then allows NHI runtime
+		 * suspend too now that the device link is established).
+		 */
+		pm_runtime_get_sync(&pdev->dev);
+
 		link = device_link_add(&pdev->dev, &nhi->pdev->dev,
 				       DL_FLAG_AUTOREMOVE_SUPPLIER |
+				       DL_FLAG_RPM_ACTIVE |
 				       DL_FLAG_PM_RUNTIME);
 		if (link) {
 			dev_dbg(&nhi->pdev->dev, "created link from %s\n",
@@ -84,6 +95,8 @@ static acpi_status tb_acpi_add_link(acpi_handle handle, u32 level, void *data,
 			dev_warn(&nhi->pdev->dev, "device link creation from %s failed\n",
 				 dev_name(&pdev->dev));
 		}
+
+		pm_runtime_put(&pdev->dev);
 	}
 
 out_put:
-- 
2.34.1