linux-kernel - [PATCH 1/1] serial: stm32: add no_console

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Date:   Tue, 19 May 2020 11:41:04 +0200
From:   Erwan Le Ray <erwan.leray@...com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jslaby@...e.com>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Alexandre Torgue <alexandre.torgue@...com>,
        Sumit Semwal <sumit.semwal@...aro.org>
CC:     <linux-serial@...r.kernel.org>,
        <linux-stm32@...md-mailman.stormreply.com>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <linux-media@...r.kernel.org>,
        <dri-devel@...ts.freedesktop.org>,
        <linaro-mm-sig@...ts.linaro.org>,
        Erwan Le Ray <erwan.leray@...com>,
        Fabrice Gasnier <fabrice.gasnier@...com>
Subject: [PATCH 1/1] serial: stm32: add no_console_suspend support

In order to display console messages in low power mode, console pins
must be kept active after suspend call.

---
Initial patch "serial: stm32: add support for no_console_suspend" was part
of "STM32 usart power improvement" series, but as dependancy to
console_suspend pinctl state has been removed to fit with Rob comment [1],
this patch has no more dependancy with any other patch of this series.

[1] https://lkml.org/lkml/2019/7/9/451

Signed-off-by: Erwan Le Ray <erwan.leray@...com>

diff --git a/drivers/tty/serial/stm32-usart.c b/drivers/tty/serial/stm32-usart.c
index 9cfcf355567a..5afd29162f6c 100644
--- a/drivers/tty/serial/stm32-usart.c
+++ b/drivers/tty/serial/stm32-usart.c
@@ -1425,7 +1425,18 @@ static int __maybe_unused stm32_serial_suspend(struct device *dev)
 	else
 		stm32_serial_enable_wakeup(port, false);
 
-	pinctrl_pm_select_sleep_state(dev);
+	/*
+	 * When "no_console_suspend" is enabled, keep the pinctrl default state
+	 * and rely on bootloader stage to restore this state upon resume.
+	 * Otherwise, apply the idle or sleep states depending on wakeup
+	 * capabilities.
+	 */
+	if (console_suspend_enabled || !uart_console(port)) {
+		if (device_may_wakeup(dev))
+			pinctrl_pm_select_idle_state(dev);
+		else
+			pinctrl_pm_select_sleep_state(dev);
+	}
 
 	return 0;
 }
-- 
2.17.1