netdev - [PATCH 1/4] can: m_can: Add hrtimer to generate software interrupt

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Date:   Wed, 19 Apr 2023 17:33:20 -0500
From:   Judith Mendez <jm@...com>
To:     Chandrasekar Ramakrishnan <rcsekar@...sung.com>,
        Wolfgang Grandegger <wg@...ndegger.com>,
        Marc Kleine-Budde <mkl@...gutronix.de>
CC:     "David S . Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Schuyler Patton <spatton@...com>, Nishanth Menon <nm@...com>,
        Vignesh Raghavendra <vigneshr@...com>,
        Tero Kristo <kristo@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Oliver Hartkopp <socketcan@...tkopp.net>,
        Judith Mendez <jm@...com>,
        <linux-arm-kernel@...ts.infradead.org>,
        <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-can@...r.kernel.org>, <netdev@...r.kernel.org>
Subject: [PATCH 1/4] can: m_can: Add hrtimer to generate software interrupt

Add an 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@...com>
---
 drivers/net/can/m_can/m_can.c          | 30 ++++++++++++++++++++++++--
 drivers/net/can/m_can/m_can.h          |  3 +++
 drivers/net/can/m_can/m_can_platform.c | 13 +++++++++--
 3 files changed, 42 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..8784bdea300a 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"
 
@@ -1587,6 +1588,11 @@ static int m_can_close(struct net_device *dev)
 	if (!cdev->is_peripheral)
 		napi_disable(&cdev->napi);
 
+	if (dev->irq < 0) {
+		dev_dbg(cdev->dev, "Disabling the hrtimer\n");
+		hrtimer_cancel(&cdev->hrtimer);
+	}
+
 	m_can_stop(dev);
 	m_can_clk_stop(cdev);
 	free_irq(dev->irq, dev);
@@ -1793,6 +1799,18 @@ static netdev_tx_t m_can_start_xmit(struct sk_buff *skb,
 	return NETDEV_TX_OK;
 }
 
+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(1));
+
+	return HRTIMER_RESTART;
+}
+
 static int m_can_open(struct net_device *dev)
 {
 	struct m_can_classdev *cdev = netdev_priv(dev);
@@ -1827,13 +1845,21 @@ static int m_can_open(struct net_device *dev)
 		}
 
 		INIT_WORK(&cdev->tx_work, m_can_tx_work_queue);
-
 		err = request_threaded_irq(dev->irq, NULL, m_can_isr,
 					   IRQF_ONESHOT,
 					   dev->name, dev);
+
 	} else {
-		err = request_irq(dev->irq, m_can_isr, IRQF_SHARED, dev->name,
+		if (dev->irq > 0)	{
+			err = request_irq(dev->irq, m_can_isr, IRQF_SHARED, dev->name,
 				  dev);
+		}
+
+		else	{
+			dev_dbg(cdev->dev, "Enabling the hrtimer\n");
+			cdev->hrtimer.function = &hrtimer_callback;
+			hrtimer_start(&cdev->hrtimer, ns_to_ktime(0), HRTIMER_MODE_REL_PINNED);
+		}
 	}
 
 	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..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..7540db74b7d0 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 +99,16 @@ 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;
+		}
+		if (IS_ERR(addr)) {
+			ret = PTR_ERR(addr);
+			goto probe_fail;
+		}
+		dev_dbg(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