Since commit a630fbf "serial: omap: Fix device tree based PM runtime" the OMAP serial driver will always try to restore its context in serial_omap_runtime_resume(). But the problem is that during driver initialization the UART context is not ready yet and, as result, first call to pm_runtime_get*() will cause UART register overwriting by all zeros. This causes Kernel boot hang in case if "earlyprintk" feature is enabled at least [1]. Unfortunately, there is no exact place in driver now where we can determine that UART context is ready - most of registers configured in serial_omap_set_termios(), but some of them in other places. More over, even if PM runtime will be disabled (blocked) during OMAP serial driver probe() execution [2],[3] it will fix only console UART, but context of other UARTs will be overwriting by all zeros during first access to the corresponding UART. To fix this issue: - introduce additional "initialized" flag and update PM runtime callback to do nothing if its not set. Set "initialized" at the end of probe(). - read current UART registers configuration in probe and use it by default. [1] http://www.spinics.net/lists/arm-kernel/msg256828.html [2] http://www.spinics.net/lists/arm-kernel/msg258062.html [3] http://www.spinics.net/lists/arm-kernel/msg258040.html CC: Tony Lindgren <tony@xxxxxxxxxxx> CC: Rajendra Nayak <rnayak@xxxxxx> CC: Felipe Balbi <balbi@xxxxxx> CC: Kevin Hilman <khilman@xxxxxxxxxx> Signed-off-by: Grygorii Strashko <grygorii.strashko@xxxxxx> --- tested on OMAP4 SDP with and without earlyprintk enabled. drivers/tty/serial/omap-serial.c | 27 ++++++++++++++++++++++++++- 1 file changed, 26 insertions(+), 1 deletion(-) diff --git a/drivers/tty/serial/omap-serial.c b/drivers/tty/serial/omap-serial.c index f39bf0c..e1e9667 100644 --- a/drivers/tty/serial/omap-serial.c +++ b/drivers/tty/serial/omap-serial.c @@ -162,6 +162,7 @@ struct uart_omap_port { struct work_struct qos_work; struct pinctrl *pins; bool is_suspending; + bool initialized; }; #define to_uart_omap_port(p) ((container_of((p), struct uart_omap_port, port))) @@ -1395,6 +1396,19 @@ static struct omap_uart_port_info *of_get_uart_port_info(struct device *dev) return omap_up_info; } +static void serial_omap_save_context_def(struct uart_omap_port *up) +{ + up->dll = serial_in(up, UART_DLL); + up->dlh = serial_in(up, UART_DLM); + up->ier = serial_in(up, UART_IER); + up->fcr = serial_in(up, UART_FCR); + up->mcr = serial_in(up, UART_MCR); + up->scr = serial_in(up, UART_OMAP_SCR); + up->efr = serial_in(up, UART_EFR); + up->lcr = serial_in(up, UART_LCR); + up->mdr1 = serial_in(up, UART_OMAP_MDR1); +} + static int serial_omap_probe(struct platform_device *pdev) { struct uart_omap_port *up; @@ -1518,10 +1532,14 @@ static int serial_omap_probe(struct platform_device *pdev) ui[up->port.line] = up; serial_omap_add_console_port(up); + serial_omap_save_context_def(up); + ret = uart_add_one_port(&serial_omap_reg, &up->port); if (ret != 0) goto err_add_port; + up->initialized = true; + pm_runtime_mark_last_busy(up->dev); pm_runtime_put_autosuspend(up->dev); return 0; @@ -1619,6 +1637,9 @@ static int serial_omap_runtime_suspend(struct device *dev) if (!up) return -EINVAL; + if (!up->initialized) + return 0; + /* * When using 'no_console_suspend', the console UART must not be * suspended. Since driver suspend is managed by runtime suspend, @@ -1652,8 +1673,12 @@ static int serial_omap_runtime_suspend(struct device *dev) static int serial_omap_runtime_resume(struct device *dev) { struct uart_omap_port *up = dev_get_drvdata(dev); + int loss_cnt; + + if (!up->initialized) + return 0; - int loss_cnt = serial_omap_get_context_loss_count(up); + loss_cnt = serial_omap_get_context_loss_count(up); if (loss_cnt < 0) { dev_dbg(dev, "serial_omap_get_context_loss_count failed : %d\n", -- 1.7.9.5 -- To unsubscribe from this list: send the line "unsubscribe linux-serial" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
