Re: [PATCH v2 1/4] can: m_can: Add hrtimer to generate software interrupt

From: Mendez, Judith
Date: Wed Apr 26 2023 - 12:12:08 EST

Hello Marc,

On 4/24/2023 3:14 PM, Marc Kleine-Budde wrote:
On 24.04.2023 14:53:59, Judith Mendez wrote:
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@xxxxxx>
---
Changelog:
v2:
1. Add poll-interval to MCAN class device to check if poll-interval propery is
present in MCAN node, this enables timer polling method.
2. Add 'polling' flag to MCAN class device to check if a device is using timer
polling method
3. Check if both timer polling and hardware interrupt are enabled for a MCAN
device, default to hardware interrupt mode if both are enabled.
4. Changed ms_to_ktime() to ns_to_ktime()
5. Removed newlines, tabs, and restructure if/else section.

drivers/net/can/m_can/m_can.c | 30 ++++++++++++++++++++-----
drivers/net/can/m_can/m_can.h | 5 +++++
drivers/net/can/m_can/m_can_platform.c | 31 ++++++++++++++++++++++++--
3 files changed, 59 insertions(+), 7 deletions(-)

diff --git a/drivers/net/can/m_can/m_can.c b/drivers/net/can/m_can/m_can.c
index a5003435802b..33e094f88da1 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>

keep the list of includes sorted

Will do.
#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 (cdev->polling) {
+ 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));

Please create a define for this

Thanks, will create a define for the 1 ms polling interval.

+
+ return HRTIMER_RESTART;
+}
+
static int m_can_open(struct net_device *dev)
{
struct m_can_classdev *cdev = netdev_priv(dev);
@@ -1827,13 +1845,15 @@ 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,
+ IRQF_ONESHOT, dev->name, dev);
+ } else if (!cdev->polling) {
+ err = request_irq(dev->irq, m_can_isr, IRQF_SHARED, dev->name,
dev);

No need to change the indention

Will fix.

+ } else {
+ dev_dbg(cdev->dev, "Start hrtimer\n");
+ cdev->hrtimer.function = &hrtimer_callback;
+ hrtimer_start(&cdev->hrtimer, ms_to_ktime(cdev->poll_interval), 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..1ba87eb23f8e 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>

keep the list of includes sorted

/* m_can lec values */
enum m_can_lec_type {
@@ -93,6 +94,10 @@ struct m_can_classdev {
int is_peripheral;
struct mram_cfg mcfg[MRAM_CFG_NUM];
+
+ struct hrtimer hrtimer;
+ u32 poll_interval;
+ u8 polling;

bool

Will use bool instead.
};
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..e899c04edc01 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"
@@ -97,11 +98,37 @@ 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");

use platform_get_irq_byname_optional(), it doesn't print an error
message.

Thanks.

- if (IS_ERR(addr) || irq < 0) {
- ret = -EINVAL;
+ if (irq == -EPROBE_DEFER) {
+ ret = -EPROBE_DEFER;
goto probe_fail;
}
+ if (IS_ERR(addr)) {
+ ret = PTR_ERR(addr);
+ goto probe_fail;
+ }

please move the error check for "addr" directly after the "addr = "
assignment.

Will do.
+
+ mcan_class->polling = 0;

No need to init as "0"


Awsome thanks.
+ if (device_property_present(mcan_class->dev, "poll-interval")) {
+ mcan_class->polling = 1;
+ }

No need for the { } here.

+
+ if (!mcan_class->polling && irq < 0) {
+ ret = -ENODATA;
-ENXIO
+ dev_dbg(mcan_class->dev, "Polling not enabled\n");

print a proper error message using dev_err_probe("IRQ %s not found and
polling not activated\n")

Why %s when MCAN requests 1 IRQ which is "int0"? If we want to print "int0", should it be hardcoded into the print error message?

+ goto probe_fail;
+ }
+
+ if (mcan_class->polling && irq > 0) {
+ mcan_class->polling = 0;
+ dev_dbg(mcan_class->dev, "Polling not enabled, hardware interrupt exists\n");
+ }
+
+ if (mcan_class->polling && irq < 0) {
+ dev_dbg(mcan_class->dev, "Polling enabled, initialize hrtimer");
+ hrtimer_init(&mcan_class->hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL_PINNED);
+ }

combine both if (mcan_class->polling) into one.

Will do.
+
/* message ram could be shared */
res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "message_ram");
if (!res) {
--
2.17.1



regards,
Judith