Re: [PATCH] serial: of-serial: add PM suspend/resume support

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Hi,

This patch might have a potential issue that cause system hard hung immediately when it accesses to registers with no clock. This could happen on many chips that mainline kernel supporting with the setting "no_console_suspend=1" during suspend time.

On 09/23/2014 04:34 PM, Jingchang Lu wrote:
This adds PM suspend/resume support for the of-serial driver
to provide power management support on devices attatched to it.

Signed-off-by: Jingchang Lu <jingchang.lu@xxxxxxxxxxxxx>
---
  drivers/tty/serial/of_serial.c | 27 +++++++++++++++++++++++++++
  1 file changed, 27 insertions(+)

diff --git a/drivers/tty/serial/of_serial.c b/drivers/tty/serial/of_serial.c
index 27981e2..8bc2563 100644
--- a/drivers/tty/serial/of_serial.c
+++ b/drivers/tty/serial/of_serial.c
@@ -240,6 +240,32 @@ static int of_platform_serial_remove(struct platform_device *ofdev)
  	return 0;
  }

+#ifdef CONFIG_PM_SLEEP
+static int of_serial_suspend(struct device *dev)
+{
+	struct of_serial_info *info = dev_get_drvdata(dev);
+
+	serial8250_suspend_port(info->line);
+	if (info->clk)
The fix would be something like this.
	if (info->clk && console_suspend_enabled)

+		clk_disable_unprepare(info->clk);
+
+	return 0;
+}
+
+static int of_serial_resume(struct device *dev)
+{
+	struct of_serial_info *info = dev_get_drvdata(dev);
+
+	if (info->clk)
Ditto.

Thanks,
-Joseph
+		clk_prepare_enable(info->clk);
+
+	serial8250_resume_port(info->line);
+
+	return 0;
+}
+#endif
+static SIMPLE_DEV_PM_OPS(of_serial_pm_ops, of_serial_suspend, of_serial_resume);
+
  /*
   * A few common types, add more as needed.
   */
@@ -271,6 +297,7 @@ static struct platform_driver of_platform_serial_driver = {
  		.name = "of_serial",
  		.owner = THIS_MODULE,
  		.of_match_table = of_platform_serial_table,
+		.pm = &of_serial_pm_ops,
  	},
  	.probe = of_platform_serial_probe,
  	.remove = of_platform_serial_remove,

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