can: m_can: allow keeping the transceiver running in suspend

Add a flag to the device class structure that leaves the chip in a
running state with rx interrupt enabled, so that an m_can device driver
can configure and use the interrupt as a wakeup source.
Signed-off-by: Martin Hundebøll <martin@geanix.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

drivers/net/can/m_can/m_can.c

@@ -2382,7 +2382,15 @@ int m_can_class_suspend(struct device *dev)
 	if (netif_running(ndev)) {
 		netif_stop_queue(ndev);
 		netif_device_detach(ndev);
-		m_can_stop(ndev);
+
+		/* leave the chip running with rx interrupt enabled if it is
+		 * used as a wake-up source.
+		 */
+		if (cdev->pm_wake_source)
+			m_can_write(cdev, M_CAN_IE, IR_RF0N);
+		else
+			m_can_stop(ndev);
+
 		m_can_clk_stop(cdev);
 	}
 
@@ -2409,11 +2417,15 @@ int m_can_class_resume(struct device *dev)
 		ret = m_can_clk_start(cdev);
 		if (ret)
 			return ret;
-		ret  = m_can_start(ndev);
-		if (ret) {
-			m_can_clk_stop(cdev);
 
-			return ret;
+		if (cdev->pm_wake_source) {
+			m_can_write(cdev, M_CAN_IE, cdev->active_interrupts);
+		} else {
+			ret  = m_can_start(ndev);
+			if (ret) {
+				m_can_clk_stop(cdev);
+				return ret;
+			}
 		}
 
 		netif_device_attach(ndev);

drivers/net/can/m_can/m_can.h

@@ -97,6 +97,7 @@ struct m_can_classdev {
 	u32 irqstatus;
 
 	int pm_clock_support;
+	int pm_wake_source;
 	int is_peripheral;
 
 	// Cached M_CAN_IE register content

drivers/net/can/m_can/m_can_pci.c

@@ -125,6 +125,7 @@ static int m_can_pci_probe(struct pci_dev *pci, const struct pci_device_id *id)
 	mcan_class->dev = &pci->dev;
 	mcan_class->net->irq = pci_irq_vector(pci, 0);
 	mcan_class->pm_clock_support = 1;
+	mcan_class->pm_wake_source = 0;
 	mcan_class->can.clock.freq = id->driver_data;
 	mcan_class->ops = &m_can_pci_ops;
 

drivers/net/can/m_can/m_can_platform.c

@@ -139,6 +139,7 @@ static int m_can_plat_probe(struct platform_device *pdev)
 
 	mcan_class->net->irq = irq;
 	mcan_class->pm_clock_support = 1;
+	mcan_class->pm_wake_source = 0;
 	mcan_class->can.clock.freq = clk_get_rate(mcan_class->cclk);
 	mcan_class->dev = &pdev->dev;
 	mcan_class->transceiver = transceiver;

drivers/net/can/m_can/tcan4x5x-core.c

@@ -411,6 +411,7 @@ static int tcan4x5x_can_probe(struct spi_device *spi)
 	priv->spi = spi;
 
 	mcan_class->pm_clock_support = 0;
+	mcan_class->pm_wake_source = 0;
 	mcan_class->can.clock.freq = freq;
 	mcan_class->dev = &spi->dev;
 	mcan_class->ops = &tcan4x5x_ops;