[RFC] PM: core: Add pm_wakeup_pending check in device suspend_noirq

[cy_huang <u0084500@gmail.com>]

From: ChiYuan Huang <cy_huang@richtek.com>

In 'dpm_suspend_noirq', it will do the sychronized_irq to guarantee all
irqs are all done, and then do any wakeup flag set.

For some peripherial deivces like as I2C/SPI, to speed up the irq handling,
it may use 'pm_stay_awake' and really handle in another thread context like
as workqueue.

But in mem suspend flow, after 'dpm_suspend_noirq" stage, the next
'pm_wakeup_pending' check will be at 'syscore_suspend'.

The checkpoint seems too late and cause I2C/SPI fail during 'noirq' to
'syscore_suspend'. But some adapter was already be marked as 'suspended'
at 'noirq' callback, any I2C/SPI xfer will return the error flag '-ESHUTDOWN'.

After the code trace, it seems all device callback will do 'pm_wakeup_pending'
check, except 'noirq'.

This patch is to add 'pm_wakeup_pending' check in 'noirq' sage to prevent this
kind of usage.

Signed-off-by: ChiYuan Huang <cy_huang@richtek.com>
---
Hi,

Is there any rule to define when I2C/SPI host controller need to mark adapter as
'suspended'?

I trace 'drivers/i2c/buses'.It seems there's no common rule, Some are 'suspend',
others may did it at 'suspend_noirq'.

---
 drivers/base/power/main.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/base/power/main.c b/drivers/base/power/main.c
index c501392..7cd7dc5 100644
--- a/drivers/base/power/main.c
+++ b/drivers/base/power/main.c
@@ -1210,6 +1210,11 @@ static int __device_suspend_noirq(struct device *dev, pm_message_t state, bool a
 	if (async_error)
 		goto Complete;
 
+	if (pm_wakeup_pending()) {
+		async_error = -EBUSY;
+		goto Complete;
+	}
+
 	if (dev->power.syscore || dev->power.direct_complete)
 		goto Complete;
 
-- 
2.7.4