can: m_can: move runtime PM enable/disable to m_can_platform

This is a preparatory patch for upcoming PCI based M_CAN devices. The current
PM implementation would cause PCI based drivers to enable PM twice, once when
the PCI device is added and a second time in m_can_class_register(). This will
cause 'Unbalanced pm_runtime_enable!' to be logged, and is a situation that
should be avoided.

Therefore, in anticipation of PCI devices, move PM enabling out from M_CAN
class registration to its only user, the m_can_platform driver.

Signed-off-by: Patrik Flykt <patrik.flykt@linux.intel.com>
Link: https://lore.kernel.org/r/20201023115800.46538-2-patrik.flykt@linux.intel.com
[mkl: m_can_plat_probe(): fix error handling
      m_can_class_register(): simplify error handling]
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

drivers/net/can/m_can/m_can.c

@@ -1826,10 +1826,9 @@ int m_can_class_register(struct m_can_classdev *m_can_dev)
 	int ret;
 
 	if (m_can_dev->pm_clock_support) {
-		pm_runtime_enable(m_can_dev->dev);
 		ret = m_can_clk_start(m_can_dev);
 		if (ret)
-			goto pm_runtime_fail;
+			return ret;
 	}
 
 	ret = m_can_dev_setup(m_can_dev);
@@ -1855,11 +1854,6 @@ int m_can_class_register(struct m_can_classdev *m_can_dev)
 	 */
 clk_disable:
 	m_can_clk_stop(m_can_dev);
-pm_runtime_fail:
-	if (ret) {
-		if (m_can_dev->pm_clock_support)
-			pm_runtime_disable(m_can_dev->dev);
-	}
 
 	return ret;
 }

drivers/net/can/m_can/m_can_platform.c

@@ -115,8 +115,15 @@ static int m_can_plat_probe(struct platform_device *pdev)
 
 	m_can_init_ram(mcan_class);
 
-	return m_can_class_register(mcan_class);
+	pm_runtime_enable(mcan_class->dev);
+	ret = m_can_class_register(mcan_class);
+	if (ret)
+		goto out_runtime_disable;
 
+	return ret;
+
+out_runtime_disable:
+	pm_runtime_disable(mcan_class->dev);
 probe_fail:
 	m_can_class_free_dev(mcan_class->net);
 	return ret;