serial: stm32: move dma_request_chan() before clk_prepare_enable()

[ Upstream commit 0d114e9ff940ebad8e88267013bf96c605a6b336 ]

If dma_request_chan() returns a PROBE_DEFER error, clk_disable_unprepare()
will be called and USART clock will be disabled. But early console can be
still active on the same USART.

While moving dma_request_chan() before clk_prepare_enable(), the clock
won't be taken in case of a DMA PROBE_DEFER error, and so it doesn't need
to be disabled. Then USART is still clocked for early console.

Fixes: a7770a4bfcf4 ("serial: stm32: defer probe for dma devices")
Reported-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Valentin Caron <valentin.caron@foss.st.com>
Link: https://lore.kernel.org/r/20221118170602.1057863-1-valentin.caron@foss.st.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/tty/serial/stm32-usart.c b/drivers/tty/serial/stm32-usart.c
index dfdbcf0..b8aed28 100644 (file)
--- a/drivers/tty/serial/stm32-usart.c
+++ b/drivers/tty/serial/stm32-usart.c
@@ -1681,22 +1681,10 @@ static int stm32_usart_serial_probe(struct platform_device *pdev)
        if (!stm32port->info)
                return -EINVAL;
 
-       ret = stm32_usart_init_port(stm32port, pdev);
-       if (ret)
-               return ret;
-
-       if (stm32port->wakeup_src) {
-               device_set_wakeup_capable(&pdev->dev, true);
-               ret = dev_pm_set_wake_irq(&pdev->dev, stm32port->port.irq);
-               if (ret)
-                       goto err_deinit_port;
-       }
-
        stm32port->rx_ch = dma_request_chan(&pdev->dev, "rx");
-       if (PTR_ERR(stm32port->rx_ch) == -EPROBE_DEFER) {
-               ret = -EPROBE_DEFER;
-               goto err_wakeirq;
-       }
+       if (PTR_ERR(stm32port->rx_ch) == -EPROBE_DEFER)
+               return -EPROBE_DEFER;
+
        /* Fall back in interrupt mode for any non-deferral error */
        if (IS_ERR(stm32port->rx_ch))
                stm32port->rx_ch = NULL;
@@ -1710,6 +1698,17 @@ static int stm32_usart_serial_probe(struct platform_device *pdev)
        if (IS_ERR(stm32port->tx_ch))
                stm32port->tx_ch = NULL;
 
+       ret = stm32_usart_init_port(stm32port, pdev);
+       if (ret)
+               goto err_dma_tx;
+
+       if (stm32port->wakeup_src) {
+               device_set_wakeup_capable(&pdev->dev, true);
+               ret = dev_pm_set_wake_irq(&pdev->dev, stm32port->port.irq);
+               if (ret)
+                       goto err_deinit_port;
+       }
+
        if (stm32port->rx_ch && stm32_usart_of_dma_rx_probe(stm32port, pdev)) {
                /* Fall back in interrupt mode */
                dma_release_channel(stm32port->rx_ch);
@@ -1746,19 +1745,11 @@ err_port:
        pm_runtime_set_suspended(&pdev->dev);
        pm_runtime_put_noidle(&pdev->dev);
 
-       if (stm32port->tx_ch) {
+       if (stm32port->tx_ch)
                stm32_usart_of_dma_tx_remove(stm32port, pdev);
-               dma_release_channel(stm32port->tx_ch);
-       }
-
        if (stm32port->rx_ch)
                stm32_usart_of_dma_rx_remove(stm32port, pdev);
 
-err_dma_rx:
-       if (stm32port->rx_ch)
-               dma_release_channel(stm32port->rx_ch);
-
-err_wakeirq:
        if (stm32port->wakeup_src)
                dev_pm_clear_wake_irq(&pdev->dev);
 
@@ -1768,6 +1759,14 @@ err_deinit_port:
 
        stm32_usart_deinit_port(stm32port);
 
+err_dma_tx:
+       if (stm32port->tx_ch)
+               dma_release_channel(stm32port->tx_ch);
+
+err_dma_rx:
+       if (stm32port->rx_ch)
+               dma_release_channel(stm32port->rx_ch);
+
        return ret;
 }