[PATCH v7 7/8] serial: qcom-geni: Enable PM runtime for serial driver

Praveen Talari
2025-07-21T17:46:49Z

The GENI serial driver currently handles power resource management
through calls to the statically defined geni_serial_resources_on() and
geni_serial_resources_off() functions. This approach reduces modularity
and limits support for platforms with diverse power management
mechanisms, including resource managed by firmware.

Improve modularity and enable better integration with platform-specific
power management, introduce support for runtime PM. Use
pm_runtime_resume_and_get() and pm_runtime_put_sync() within the
qcom_geni_serial_pm() callback to control resource power state
transitions based on UART power state changes.

Reviewed-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Signed-off-by: Praveen Talari <quic_ptalari@quicinc.com>
---
v6 -> v7
From Bjorn:
- used devm_pm_runtime_enable() instead of pm_runtime_enable()
- updated commit text.

v5 -> v6
- added reviewed-by tag in commit
- added __maybe_unused to PM callback functions to avoid
warnings of defined but not used
---
drivers/tty/serial/qcom_geni_serial.c | 24 ++++++++++++++++++++++--
1 file changed, 22 insertions(+), 2 deletions(-)

diff --git a/drivers/tty/serial/qcom_geni_serial.c b/drivers/tty/serial/qcom_geni_serial.c
index 81f385d900d0..aa08de659e34 100644
--- a/drivers/tty/serial/qcom_geni_serial.c
+++ b/drivers/tty/serial/qcom_geni_serial.c
@@ -1713,10 +1713,10 @@ static void qcom_geni_serial_pm(struct uart_port *uport,
old_state = UART_PM_STATE_OFF;

if (new_state == UART_PM_STATE_ON && old_state == UART_PM_STATE_OFF)
- geni_serial_resources_on(uport);
+ pm_runtime_resume_and_get(uport->dev);
else if (new_state == UART_PM_STATE_OFF &&
old_state == UART_PM_STATE_ON)
- geni_serial_resources_off(uport);
+ pm_runtime_put_sync(uport->dev);

}

@@ -1878,6 +1878,8 @@ static int qcom_geni_serial_probe(struct platform_device *pdev)
if (ret)
return ret;

+ devm_pm_runtime_enable(port->se.dev);
+
ret = uart_add_one_port(drv, uport);
if (ret)
return ret;
@@ -1909,6 +1911,22 @@ static void qcom_geni_serial_remove(struct platform_device *pdev)
uart_remove_one_port(drv, &port->uport);
}

+static int __maybe_unused qcom_geni_serial_runtime_suspend(struct device *dev)
+{
+ struct qcom_geni_serial_port *port = dev_get_drvdata(dev);
+ struct uart_port *uport = &port->uport;
+
+ return geni_serial_resources_off(uport);
+}
+
+static int __maybe_unused qcom_geni_serial_runtime_resume(struct device *dev)
+{
+ struct qcom_geni_serial_port *port = dev_get_drvdata(dev);
+ struct uart_port *uport = &port->uport;
+
+ return geni_serial_resources_on(uport);
+}
+
static int qcom_geni_serial_suspend(struct device *dev)
{
struct qcom_geni_serial_port *port = dev_get_drvdata(dev);
@@ -1952,6 +1970,8 @@ static const struct qcom_geni_device_data qcom_geni_uart_data = {
};

static const struct dev_pm_ops qcom_geni_serial_pm_ops = {
+ SET_RUNTIME_PM_OPS(qcom_geni_serial_runtime_suspend,
+ qcom_geni_serial_runtime_resume, NULL)
SYSTEM_SLEEP_PM_OPS(qcom_geni_serial_suspend, qcom_geni_serial_resume)
};

--
2.17.1