[PATCH v2 1/1] mfd: intel-lpss: Fix too early PM enablement in the ACPI ->probe()

[Andy Shevchenko <andriy.shevchenko@linux.intel.com>]

The runtime PM callback may be called as soon as the runtime PM facility
is enabled and activated. It means that ->suspend() may be called before
we finish probing the device in the ACPI case. Hence, NULL pointer
dereference:

  intel-lpss INT34BA:00: IRQ index 0 not found
  BUG: kernel NULL pointer dereference, address: 0000000000000030
  ...
  Workqueue: pm pm_runtime_work
  RIP: 0010:intel_lpss_suspend+0xb/0x40 [intel_lpss]

To fix this, first try to register the device and only after that enable
runtime PM facility.

Fixes: 4b45efe85263 ("mfd: Add support for Intel Sunrisepoint LPSS devices")
Reported-by: Orlando Chamberlain <redecorating@protonmail.com>
Reported-by: Aditya Garg <gargaditya08@live.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Tested-by: Aditya Garg <gargaditya08@live.com>
---
v2: added tag (Aditya), returned 0 explicitly at the end of ->probe()
 drivers/mfd/intel-lpss-acpi.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/mfd/intel-lpss-acpi.c b/drivers/mfd/intel-lpss-acpi.c
index 3f1d976eb67c..f2ea6540a01e 100644
--- a/drivers/mfd/intel-lpss-acpi.c
+++ b/drivers/mfd/intel-lpss-acpi.c
@@ -136,6 +136,7 @@ static int intel_lpss_acpi_probe(struct platform_device *pdev)
 {
 	struct intel_lpss_platform_info *info;
 	const struct acpi_device_id *id;
+	int ret;
 
 	id = acpi_match_device(intel_lpss_acpi_ids, &pdev->dev);
 	if (!id)
@@ -149,10 +150,14 @@ static int intel_lpss_acpi_probe(struct platform_device *pdev)
 	info->mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 	info->irq = platform_get_irq(pdev, 0);
 
+	ret = intel_lpss_probe(&pdev->dev, info);
+	if (ret)
+		return ret;
+
 	pm_runtime_set_active(&pdev->dev);
 	pm_runtime_enable(&pdev->dev);
 
-	return intel_lpss_probe(&pdev->dev, info);
+	return 0;
 }
 
 static int intel_lpss_acpi_remove(struct platform_device *pdev)
-- 
2.33.0