[RFC PATCH 5/5] can: m_can: Add hrtimer to generate software interrupt

[Judith Mendez]

Add a hrtimer to MCAN struct. Each MCAN will have its own
hrtimer instantiated if there is no hardware interrupt found.

The hrtimer will generate a software interrupt every 1 ms. In
hrtimer callback, we check if there is a transaction pending by
reading a register, then process by calling the isr if there is.

Signed-off-by: Judith Mendez <jm@xxxxxx>
---
 drivers/net/can/m_can/m_can.c          | 24 ++++++++++++++++++++++--
 drivers/net/can/m_can/m_can.h          |  3 +++
 drivers/net/can/m_can/m_can_platform.c |  9 +++++++--
 3 files changed, 32 insertions(+), 4 deletions(-)

diff --git a/drivers/net/can/m_can/m_can.c b/drivers/net/can/m_can/m_can.c
index 8e83d6963d85..bb9d53f4d3cc 100644
--- a/drivers/net/can/m_can/m_can.c
+++ b/drivers/net/can/m_can/m_can.c
@@ -23,6 +23,7 @@
 #include <linux/pinctrl/consumer.h>
 #include <linux/platform_device.h>
 #include <linux/pm_runtime.h>
+#include <linux/hrtimer.h>
 
 #include "m_can.h"
 
@@ -1584,6 +1585,11 @@ static int m_can_close(struct net_device *dev)
 	if (!cdev->is_peripheral)
 		napi_disable(&cdev->napi);
 
+	if (dev->irq < 0) {
+		dev_info(cdev->dev, "Disabling the hrtimer\n");
+		hrtimer_cancel(&cdev->hrtimer);
+	}
+
 	m_can_stop(dev);
 	m_can_clk_stop(cdev);
 	free_irq(dev->irq, dev);
@@ -1792,6 +1798,19 @@ static netdev_tx_t m_can_start_xmit(struct sk_buff *skb,
 	return NETDEV_TX_OK;
 }
 
+enum hrtimer_restart hrtimer_callback(struct hrtimer *timer)
+{
+	irqreturn_t ret;
+	struct m_can_classdev *cdev =
+		container_of(timer, struct m_can_classdev, hrtimer);
+
+	ret = m_can_isr(0, cdev->net);
+
+	hrtimer_forward_now(timer, ns_to_ktime(5 * NSEC_PER_MSEC));
+
+	return HRTIMER_RESTART;
+}
+
 static int m_can_open(struct net_device *dev)
 {
 	struct m_can_classdev *cdev = netdev_priv(dev);
@@ -1836,8 +1855,9 @@ static int m_can_open(struct net_device *dev)
 	}
 
 	if (err < 0) {
-		netdev_err(dev, "failed to request interrupt\n");
-		goto exit_irq_fail;
+		dev_info(cdev->dev, "Enabling the hrtimer\n");
+		cdev->hrtimer.function = &hrtimer_callback;
+		hrtimer_start(&cdev->hrtimer, ns_to_ktime(0), HRTIMER_MODE_REL_PINNED);
 	}
 
 	/* start the m_can controller */
diff --git a/drivers/net/can/m_can/m_can.h b/drivers/net/can/m_can/m_can.h
index a839dc71dc9b..ed046d77fdb9 100644
--- a/drivers/net/can/m_can/m_can.h
+++ b/drivers/net/can/m_can/m_can.h
@@ -28,6 +28,7 @@
 #include <linux/pm_runtime.h>
 #include <linux/slab.h>
 #include <linux/uaccess.h>
+#include <linux/hrtimer.h>
 
 /* m_can lec values */
 enum m_can_lec_type {
@@ -93,6 +94,8 @@ struct m_can_classdev {
 	int is_peripheral;
 
 	struct mram_cfg mcfg[MRAM_CFG_NUM];
+
+	struct hrtimer hrtimer;
 };
 
 struct m_can_classdev *m_can_class_allocate_dev(struct device *dev, int sizeof_priv);
diff --git a/drivers/net/can/m_can/m_can_platform.c b/drivers/net/can/m_can/m_can_platform.c
index 9c1dcf838006..53e1648e9dab 100644
--- a/drivers/net/can/m_can/m_can_platform.c
+++ b/drivers/net/can/m_can/m_can_platform.c
@@ -7,6 +7,7 @@
 
 #include <linux/phy/phy.h>
 #include <linux/platform_device.h>
+#include <linux/hrtimer.h>
 
 #include "m_can.h"
 
@@ -98,8 +99,12 @@ static int m_can_plat_probe(struct platform_device *pdev)
 	addr = devm_platform_ioremap_resource_byname(pdev, "m_can");
 	irq = platform_get_irq_byname(pdev, "int0");
 	if (IS_ERR(addr) || irq < 0) {
-		ret = -EINVAL;
-		goto probe_fail;
+		if (irq == -EPROBE_DEFER) {
+			ret = -EPROBE_DEFER;
+			goto probe_fail;
+		}
+		dev_info(mcan_class->dev, "Failed to get irq, initialize hrtimer\n");
+		hrtimer_init(&mcan_class->hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL_PINNED);
 	}
 
 	/* message ram could be shared */
-- 
2.17.1