[PATCH 1/1] usb: host: tegra: Prevent host controller crash when OTG port is used

[Wayne Chang <waynec@nvidia.com>]

From: Jim Lin <jilin@nvidia.com>

When a USB device is connected to the OTG port, the tegra_xhci_id_work()
routine transitions the PHY to host mode and calls xhci_hub_control()
with the SetPortFeature command to enable port power.

In certain cases, the XHCI controller may be in a low-power state
when this operation occurs. If xhci_hub_control() is invoked while
the controller is suspended, the PORTSC register may return 0xFFFFFFFF,
indicating a read failure. This causes xhci_hc_died() to be triggered,
leading to host controller shutdown.

Example backtrace:
[  105.445736] Workqueue: events tegra_xhci_id_work
[  105.445747]  dump_backtrace+0x0/0x1e8
[  105.445759]  xhci_hc_died.part.48+0x40/0x270
[  105.445769]  tegra_xhci_set_port_power+0xc0/0x240
[  105.445774]  tegra_xhci_id_work+0x130/0x240

To prevent this, ensure the controller is fully resumed before
interacting with hardware registers by calling pm_runtime_get_sync()
prior to the host mode transition and xhci_hub_control().

Fixes: f836e7843036 ("usb: xhci-tegra: Add OTG support")
Cc: stable@vger.kernel.org
Signed-off-by: Jim Lin <jilin@nvidia.com>
Signed-off-by: Wayne Chang <waynec@nvidia.com>
---
 drivers/usb/host/xhci-tegra.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/usb/host/xhci-tegra.c b/drivers/usb/host/xhci-tegra.c
index 22dc86fb5254..70ec36e4ff5f 100644
--- a/drivers/usb/host/xhci-tegra.c
+++ b/drivers/usb/host/xhci-tegra.c
@@ -1364,6 +1364,7 @@ static void tegra_xhci_id_work(struct work_struct *work)
 	tegra->otg_usb3_port = tegra_xusb_padctl_get_usb3_companion(tegra->padctl,
 								    tegra->otg_usb2_port);
 
+	pm_runtime_get_sync(tegra->dev);
 	if (tegra->host_mode) {
 		/* switch to host mode */
 		if (tegra->otg_usb3_port >= 0) {
@@ -1393,6 +1394,7 @@ static void tegra_xhci_id_work(struct work_struct *work)
 		}
 
 		tegra_xhci_set_port_power(tegra, true, true);
+		pm_runtime_mark_last_busy(tegra->dev);
 
 	} else {
 		if (tegra->otg_usb3_port >= 0)
@@ -1400,6 +1402,7 @@ static void tegra_xhci_id_work(struct work_struct *work)
 
 		tegra_xhci_set_port_power(tegra, true, false);
 	}
+	pm_runtime_put_autosuspend(tegra->dev);
 }
 
 #if IS_ENABLED(CONFIG_PM) || IS_ENABLED(CONFIG_PM_SLEEP)
-- 
2.25.1