[PATCH v6 2/2] can: m_can: Add hrtimer to generate software interrupt

[Judith Mendez <jm@ti.com>]

Add an hrtimer to MCAN class device. Each MCAN will have its own
hrtimer instantiated if there is no hardware interrupt found and
poll-interval property is defined in device tree M_CAN node.

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@ti.com>
---
Changelog:
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          | 31 ++++++++++++++++++++++-
 drivers/net/can/m_can/m_can.h          |  4 +++
 drivers/net/can/m_can/m_can_platform.c | 35 +++++++++++++++++++++++---
 3 files changed, 66 insertions(+), 4 deletions(-)

diff --git a/drivers/net/can/m_can/m_can.c b/drivers/net/can/m_can/m_can.c
index a5003435802b..cfb3e433c0dd 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 (cdev->polling) {
+		dev_dbg(cdev->dev, "Start hrtimer\n");
+		hrtimer_start(&cdev->hrtimer, ms_to_ktime(HRTIMER_POLL_INTERVAL),
+			      HRTIMER_MODE_REL_PINNED);
+	}
+
 	return 0;
 }
 
@@ -1571,6 +1581,11 @@ static void m_can_stop(struct net_device *dev)
 	/* disable all interrupts */
 	m_can_disable_all_interrupts(cdev);
 
+	if (cdev->polling) {
+		dev_dbg(cdev->dev, "Disabling the hrtimer\n");
+		hrtimer_cancel(&cdev->hrtimer);
+	}
+
 	/* Set init mode to disengage from the network */
 	m_can_config_endisable(cdev, true);
 
@@ -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);
@@ -1831,9 +1858,11 @@ 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 {
+	} else if (!cdev->polling) {
 		err = request_irq(dev->irq, m_can_isr, IRQF_SHARED, dev->name,
 				  dev);
+	} else {
+		cdev->hrtimer.function = &hrtimer_callback;
 	}
 
 	if (err < 0) {
diff --git a/drivers/net/can/m_can/m_can.h b/drivers/net/can/m_can/m_can.h
index a839dc71dc9b..e9db5cce4e68 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 +94,9 @@ struct m_can_classdev {
 	int is_peripheral;
 
 	struct mram_cfg mcfg[MRAM_CFG_NUM];
+
+	struct hrtimer hrtimer;
+	bool polling;
 };
 
 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..3e60cebd9d12 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 +97,40 @@ 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;
 	}
 
+	irq = platform_get_irq_byname_optional(pdev, "int0");
+	if (irq == -EPROBE_DEFER) {
+		ret = -EPROBE_DEFER;
+		goto probe_fail;
+	}
+
+	if (device_property_present(mcan_class->dev, "interrupts") ||
+	    device_property_present(mcan_class->dev, "interrupt-names"))
+		mcan_class->polling = false;
+	else
+		mcan_class->polling = true;
+
+	if (!mcan_class->polling && irq < 0) {
+		ret = -ENXIO;
+		dev_err_probe(mcan_class->dev, ret, "IRQ int0 not found, polling not activated\n");
+		goto probe_fail;
+	}
+
+	if (mcan_class->polling) {
+		if (irq > 0) {
+			mcan_class->polling = false;
+			dev_info(mcan_class->dev, "Polling enabled, using hardware IRQ\n");
+		} else {
+			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) {
-- 
2.17.1