4.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Peter Shih <pihsun@xxxxxxxxxxxx> commit 100bc3e2bebf95506da57cbdf5f26b25f6da4c81 upstream. serial8250_register_8250_port calls uart_config_port, which calls config_port on the port before it tries to power on the port. So we need the port to be on before calling serial8250_register_8250_port. Change the code to always do a runtime resume in probe before registering port, and always do a runtime suspend in remove. This basically reverts the change in commit 68e5fc4a255a ("tty: serial: 8250_mtk: use pm_runtime callbacks for enabling"), but still use pm_runtime callbacks. Fixes: 68e5fc4a255a ("tty: serial: 8250_mtk: use pm_runtime callbacks for enabling") Signed-off-by: Peter Shih <pihsun@xxxxxxxxxxxx> Cc: stable <stable@xxxxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- drivers/tty/serial/8250/8250_mtk.c | 16 +++++++--------- 1 file changed, 7 insertions(+), 9 deletions(-) --- a/drivers/tty/serial/8250/8250_mtk.c +++ b/drivers/tty/serial/8250/8250_mtk.c @@ -231,17 +231,17 @@ static int mtk8250_probe(struct platform platform_set_drvdata(pdev, data); - pm_runtime_enable(&pdev->dev); - if (!pm_runtime_enabled(&pdev->dev)) { - err = mtk8250_runtime_resume(&pdev->dev); - if (err) - return err; - } + err = mtk8250_runtime_resume(&pdev->dev); + if (err) + return err; data->line = serial8250_register_8250_port(&uart); if (data->line < 0) return data->line; + pm_runtime_set_active(&pdev->dev); + pm_runtime_enable(&pdev->dev); + return 0; } @@ -252,13 +252,11 @@ static int mtk8250_remove(struct platfor pm_runtime_get_sync(&pdev->dev); serial8250_unregister_port(data->line); + mtk8250_runtime_suspend(&pdev->dev); pm_runtime_disable(&pdev->dev); pm_runtime_put_noidle(&pdev->dev); - if (!pm_runtime_status_suspended(&pdev->dev)) - mtk8250_runtime_suspend(&pdev->dev); - return 0; }