serial: stm32: do not call pm_runtime before startup and after shutdown

VCASTM · ADESTM · commit 92fd91dfd3fe · 2026-06-01T16:30:14.000+02:00
The driver failed to call pm_runtime_resume before the shutdown routine because tty_port is uninitialized when shutdown is called. For example the bit USART_CR1_RXNEIE is correctly set during the runtime_suspend routine but if we close the port while the device is suspended: the runtime_resume returns immediately due to the !tty_port_initialized condition and the bit USART_CR1_RXNEIE is never cleared. That will cause issues at the next startup. To solve this, the !tty_port_initialized condition is removed and replaced by a boolean "started", which is active when the runtime routines can be done after port startup is complete. - After a probe the device is considered suspended - The startup calls a pm_get but the runtime_resume routine returns immediately. - The startup calls a pm_put and the runtime_suspend routine is executed normally as the driver has completed its startup function. - The shutdown calls a pm_get and the runtime_resume routine is executed normally. - The shutdown calls a pm_put but the runtime_suspend routine returns immediately. - The remove forces the device to suspended state. Signed-off-by: Valentin Caron <valentin.caron@foss.st.com> Change-Id: Ibf8210021aebc3a7bd144c06c080d378b8928b66 Reviewed-on: https://gerrit.st.com/c/mpu/oe/st/linux-stm32/+/563753 ACI: CITOOLS <MDG-smet-aci-reviews@list.st.com> Reviewed-by: Amelie DELAUNAY <amelie.delaunay@foss.st.com> Domain-Review: Amelie DELAUNAY <amelie.delaunay@foss.st.com> ACI: CIBUILD <MDG-smet-aci-builds@list.st.com>
diff --git a/drivers/tty/serial/stm32-usart.c b/drivers/tty/serial/stm32-usart.c
@@ -1369,7 +1369,7 @@ static int stm32_usart_startup(struct uart_port *port)
 	u32 val;
 	int ret;
 
-	pm_runtime_get(port->dev);
+	pm_runtime_get_sync(port->dev);
 
 	ret = request_irq(port->irq, stm32_usart_interrupt, 0, name, port);
 	if (ret)
@@ -1398,9 +1398,11 @@ static int stm32_usart_startup(struct uart_port *port)
 	val = stm32_port->cr1_irq | USART_CR1_RE | BIT(cfg->uart_enable_bit);
 	stm32_usart_set_bits(port, ofs->cr1, val);
 
+	stm32_port->started = true;
+
 out:
 	pm_runtime_mark_last_busy(port->dev);
-	pm_runtime_put_autosuspend(port->dev);
+	pm_runtime_put_sync_autosuspend(port->dev);
 
 	return ret;
 }
@@ -1413,7 +1415,9 @@ static void stm32_usart_shutdown(struct uart_port *port)
 	u32 val, isr;
 	int ret;
 
-	pm_runtime_get(port->dev);
+	pm_runtime_get_sync(port->dev);
+
+	stm32_port->started = false;
 
 	ret = readl_relaxed_poll_timeout(port->membase + ofs->isr,
 					 isr, (isr & USART_SR_TC),
@@ -1453,8 +1457,7 @@ static void stm32_usart_shutdown(struct uart_port *port)
 
 	stm32_usart_clr_bits(port, ofs->cr1, val);
 
-	pm_runtime_mark_last_busy(port->dev);
-	pm_runtime_put_autosuspend(port->dev);
+	pm_runtime_put_sync_suspend(port->dev);
 
 	free_irq(port->irq, port);
 }
@@ -2198,7 +2201,6 @@ static int stm32_usart_serial_probe(struct platform_device *pdev)
 	if (ret)
 		goto err_rtor;
 
-	pm_runtime_set_active(&pdev->dev);
 	pm_runtime_use_autosuspend(&pdev->dev);
 	pm_runtime_set_autosuspend_delay(&pdev->dev, STM32_USART_AUTOSUSPEND_DELAY_MS);
 	pm_runtime_enable(&pdev->dev);
@@ -2246,7 +2248,6 @@ static int stm32_usart_serial_remove(struct platform_device *pdev)
 
 	pm_runtime_disable(&pdev->dev);
 	pm_runtime_set_suspended(&pdev->dev);
-	pm_runtime_put_noidle(&pdev->dev);
 
 	stm32_usart_clr_bits(port, ofs->cr1, USART_CR1_PEIE);
 
@@ -2440,7 +2441,7 @@ static int __maybe_unused stm32_usart_serial_en_wakeup(struct uart_port *port,
 	unsigned int size = 0;
 	unsigned long flags;
 
-	if (!device_can_wakeup(port->dev) || !tty_port_initialized(tport))
+	if (!device_can_wakeup(port->dev) || !stm32_port->started)
 		return 0;
 
 	/*
diff --git a/drivers/tty/serial/stm32-usart.h b/drivers/tty/serial/stm32-usart.h
@@ -240,6 +240,7 @@ struct stm32_port {
 	unsigned int tx_dma_bytes;
 	bool tx_dma_busy;	 /* dma tx transaction in progress */
 	bool rx_dma_busy;	 /* dma rx transaction in progress */
+	bool started;		/* to enable runtime_resume/suspend between startup and shutdown */
 	bool throttled;		 /* port throttled            */
 	bool hw_flow_control;
 	bool swap;		 /* swap RX & TX pins */
