[PATCH v8 2/2] can: m_can: Add hrtimer to generate software interrupt

[Judith Mendez]

Introduce timer polling method to MCAN since some SoCs may not
have M_CAN interrupt routed to A53 Linux and do not have
interrupt property in device tree M_CAN node.

On AM62x SoC, MCANs on MCU domain do not have hardware interrupt
routed to A53 Linux, instead they will use timer polling method.

Add an hrtimer to MCAN class device. Each MCAN will have its own
hrtimer instantiated if there is no hardware interrupt found in
device tree M_CAN node. The timer 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>
---
Changelog:
v8:
- Cancel hrtimer after interrupts in m_can_stop
- Move assignment of hrtimer_callback to m_can_class_register()
- Initialize irq = 0 if polling mode is used
- Add reson for polling mode in commit msg
- Remove unrelated change
- Remove polling flag
v7:
- Clean up m_can_platform.c if/else section after removing poll-interval
- Remove poll-interval from patch description
v6:
- Move hrtimer stop/start function calls to m_can_open and m_can_close to
support power suspend/resume
v5:
- Change dev_dbg to dev_info if hardware interrupt exists and polling
is enabled
v4:
- No changes
v3:
- Create a define for 1 ms polling interval
- Change plarform_get_irq to optional to not print error msg
v2:
- Add functionality to check for 'poll-interval' property in MCAN node 
- Add 'polling' flag in driver to check if device is using polling method
- Check for timer polling and hardware interrupt cases, default to
hardware interrupt method
- Change ns_to_ktime() to ms_to_ktime()
---
 drivers/net/can/m_can/m_can.c          | 34 ++++++++++++++++++++++++--
 drivers/net/can/m_can/m_can.h          |  3 +++
 drivers/net/can/m_can/m_can_platform.c | 24 +++++++++++++++---
 3 files changed, 56 insertions(+), 5 deletions(-)

diff --git a/drivers/net/can/m_can/m_can.c b/drivers/net/can/m_can/m_can.c
index a5003435802b..d1d1de94e590 100644
--- a/drivers/net/can/m_can/m_can.c
+++ b/drivers/net/can/m_can/m_can.c
@@ -11,6 +11,7 @@
 #include <linux/bitfield.h>
 #include <linux/can/dev.h>
 #include <linux/ethtool.h>
+#include <linux/hrtimer.h>
 #include <linux/interrupt.h>
 #include <linux/io.h>
 #include <linux/iopoll.h>
@@ -308,6 +309,9 @@ enum m_can_reg {
 #define TX_EVENT_MM_MASK	GENMASK(31, 24)
 #define TX_EVENT_TXTS_MASK	GENMASK(15, 0)
 
+/* Hrtimer polling interval */
+#define HRTIMER_POLL_INTERVAL		1
+
 /* The ID and DLC registers are adjacent in M_CAN FIFO memory,
  * and we can save a (potentially slow) bus round trip by combining
  * reads and writes to them.
@@ -1414,6 +1418,12 @@ static int m_can_start(struct net_device *dev)
 
 	m_can_enable_all_interrupts(cdev);
 
+	if (dev->irq == 0) {
+		dev_dbg(cdev->dev, "Start hrtimer\n");
+		hrtimer_start(&cdev->hrtimer, ms_to_ktime(HRTIMER_POLL_INTERVAL),
+			      HRTIMER_MODE_REL_PINNED);
+	}
+
 	return 0;
 }
 
@@ -1568,6 +1578,11 @@ static void m_can_stop(struct net_device *dev)
 {
 	struct m_can_classdev *cdev = netdev_priv(dev);
 
+	if (dev->irq == 0) {
+		dev_dbg(cdev->dev, "Stop hrtimer\n");
+		hrtimer_cancel(&cdev->hrtimer);
+	}
+
 	/* disable all interrupts */
 	m_can_disable_all_interrupts(cdev);
 
@@ -1793,6 +1808,18 @@ static netdev_tx_t m_can_start_xmit(struct sk_buff *skb,
 	return NETDEV_TX_OK;
 }
 
+static enum hrtimer_restart hrtimer_callback(struct hrtimer *timer)
+{
+	struct m_can_classdev *cdev = container_of(timer, struct
+						   m_can_classdev, hrtimer);
+
+	m_can_isr(0, cdev->net);
+
+	hrtimer_forward_now(timer, ms_to_ktime(HRTIMER_POLL_INTERVAL));
+
+	return HRTIMER_RESTART;
+}
+
 static int m_can_open(struct net_device *dev)
 {
 	struct m_can_classdev *cdev = netdev_priv(dev);
@@ -1831,10 +1858,10 @@ static int m_can_open(struct net_device *dev)
 		err = request_threaded_irq(dev->irq, NULL, m_can_isr,
 					   IRQF_ONESHOT,
 					   dev->name, dev);
-	} else {
+	}
+	if (dev->irq > 0)
 		err = request_irq(dev->irq, m_can_isr, IRQF_SHARED, dev->name,
 				  dev);
-	}
 
 	if (err < 0) {
 		netdev_err(dev, "failed to request interrupt\n");
@@ -2027,6 +2054,9 @@ int m_can_class_register(struct m_can_classdev *cdev)
 			goto clk_disable;
 	}
 
+	if (cdev->net->irq == 0)
+		cdev->hrtimer.function = &hrtimer_callback;
+
 	ret = m_can_dev_setup(cdev);
 	if (ret)
 		goto rx_offload_del;
diff --git a/drivers/net/can/m_can/m_can.h b/drivers/net/can/m_can/m_can.h
index a839dc71dc9b..2ac18ac867a4 100644
--- a/drivers/net/can/m_can/m_can.h
+++ b/drivers/net/can/m_can/m_can.h
@@ -15,6 +15,7 @@
 #include <linux/device.h>
 #include <linux/dma-mapping.h>
 #include <linux/freezer.h>
+#include <linux/hrtimer.h>
 #include <linux/interrupt.h>
 #include <linux/io.h>
 #include <linux/iopoll.h>
@@ -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 94dc82644113..a7ab2c8b55d1 100644
--- a/drivers/net/can/m_can/m_can_platform.c
+++ b/drivers/net/can/m_can/m_can_platform.c
@@ -5,6 +5,7 @@
 //
 // Copyright (C) 2018-19 Texas Instruments Incorporated - http://www.ti.com/
 
+#include <linux/hrtimer.h>
 #include <linux/phy/phy.h>
 #include <linux/platform_device.h>
 
@@ -96,12 +97,29 @@ static int m_can_plat_probe(struct platform_device *pdev)
 		goto probe_fail;
 
 	addr = devm_platform_ioremap_resource_byname(pdev, "m_can");
-	irq = platform_get_irq_byname(pdev, "int0");
-	if (IS_ERR(addr) || irq < 0) {
-		ret = -EINVAL;
+	if (IS_ERR(addr)) {
+		ret = PTR_ERR(addr);
 		goto probe_fail;
 	}
 
+	if (device_property_present(mcan_class->dev, "interrupts") ||
+	    device_property_present(mcan_class->dev, "interrupt-names")) {
+		irq = platform_get_irq_byname(pdev, "int0");
+		if (irq == -EPROBE_DEFER) {
+			ret = -EPROBE_DEFER;
+			goto probe_fail;
+		}
+		if (irq < 0) {
+			ret = -EINVAL;
+			goto probe_fail;
+		}
+	} else {
+		irq = 0;
+		dev_dbg(mcan_class->dev, "Polling enabled, initialize hrtimer");
+		hrtimer_init(&mcan_class->hrtimer, CLOCK_MONOTONIC,
+			     HRTIMER_MODE_REL_PINNED);
+	}
+
 	/* message ram could be shared */
 	res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "message_ram");
 	if (!res) {
-- 
2.34.1