[PATCH v1] serial: qcom-geni: Fix pinctrl deadlock on runtime resume

[Praveen Talari]

A deadlock is observed in the qcom_geni_serial driver during runtime
resume. This occurs when the pinctrl subsystem reconfigures device pins
via msm_pinmux_set_mux() while the serial device's interrupt is an
active wakeup source. msm_pinmux_set_mux() calls disable_irq() or
__synchronize_irq(), conflicting with the active wakeup state and
causing the IRQ thread to enter an uninterruptible (D-state) sleep,
leading to system instability.

The critical call trace leading to the deadlock is:

    Call trace:
    __switch_to+0xe0/0x120
    __schedule+0x39c/0x978
    schedule+0x5c/0xf8
    __synchronize_irq+0x88/0xb4
    disable_irq+0x3c/0x4c
    msm_pinmux_set_mux+0x508/0x644
    pinmux_enable_setting+0x190/0x2dc
    pinctrl_commit_state+0x13c/0x208
    pinctrl_pm_select_default_state+0x4c/0xa4
    geni_se_resources_on+0xe8/0x154
    qcom_geni_serial_runtime_resume+0x4c/0x88
    pm_generic_runtime_resume+0x2c/0x44
    __genpd_runtime_resume+0x30/0x80
    genpd_runtime_resume+0x114/0x29c
    __rpm_callback+0x48/0x1d8
    rpm_callback+0x6c/0x78
    rpm_resume+0x530/0x750
    __pm_runtime_resume+0x50/0x94
    handle_threaded_wake_irq+0x30/0x94
    irq_thread_fn+0x2c/xa8
    irq_thread+0x160/x248
    kthread+0x110/x114
    ret_from_fork+0x10/x20

To resolve this, explicitly manage the wakeup IRQ state within the
runtime suspend/resume callbacks. In the runtime resume callback, call
disable_irq_wake() before enabling resources. This preemptively
removes the "wakeup" capability from the IRQ, allowing subsequent
interrupt management calls to proceed without conflict. An error path
re-enables the wakeup IRQ if resource enablement fails.

Conversely, in runtime suspend, call enable_irq_wake() after resources
are disabled. This ensures the interrupt is configured as a wakeup
source only once the device has fully entered its low-power state. An
error path handles disabling the wakeup IRQ if the suspend operation
fails.

Fixes: 1afa70632c39 ("serial: qcom-geni: Enable PM runtime for serial driver")
Signed-off-by: Praveen Talari <praveen.talari@xxxxxxxxxxxxxxxx>
---
 drivers/tty/serial/qcom_geni_serial.c | 22 ++++++++++++++++++++--
 1 file changed, 20 insertions(+), 2 deletions(-)

diff --git a/drivers/tty/serial/qcom_geni_serial.c b/drivers/tty/serial/qcom_geni_serial.c
index 0fdda3a1e70b..4f5ea28dfe8f 100644
--- a/drivers/tty/serial/qcom_geni_serial.c
+++ b/drivers/tty/serial/qcom_geni_serial.c
@@ -1926,8 +1926,17 @@ static int __maybe_unused qcom_geni_serial_runtime_suspend(struct device *dev)
 	struct uart_port *uport = &port->uport;
 	int ret = 0;
 
-	if (port->dev_data->power_state)
+	if (port->dev_data->power_state) {
 		ret = port->dev_data->power_state(uport, false);
+		if (ret) {
+			if (device_can_wakeup(dev))
+				disable_irq_wake(port->wakeup_irq);
+			return ret;
+		}
+	}
+
+	if (device_can_wakeup(dev))
+		enable_irq_wake(port->wakeup_irq);
 
 	return ret;
 }
@@ -1938,8 +1947,17 @@ static int __maybe_unused qcom_geni_serial_runtime_resume(struct device *dev)
 	struct uart_port *uport = &port->uport;
 	int ret = 0;
 
-	if (port->dev_data->power_state)
+	if (device_can_wakeup(dev))
+		disable_irq_wake(port->wakeup_irq);
+
+	if (port->dev_data->power_state) {
 		ret = port->dev_data->power_state(uport, true);
+		if (ret) {
+			if (device_can_wakeup(dev))
+				enable_irq_wake(port->wakeup_irq);
+			return ret;
+		}
+	}
 
 	return ret;
 }

base-commit: 3e8e5822146bc396d2a7e5fbb7be13271665522a
-- 
2.34.1