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

[Marc Kleine-Budde]

On 19.04.2023 17:33:20, Judith Mendez wrote:
> 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@xxxxxx>
> ---
>  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);
> +

nitpick:
Please remove these 2 newline changes.

>  	} else {
> -		err = request_irq(dev->irq, m_can_isr, IRQF_SHARED, dev->name,
> +		if (dev->irq > 0)	{

Please follow the kernel coding style and use a space not a tab after
the closing ")" of the "if".

> +			err = request_irq(dev->irq, m_can_isr, IRQF_SHARED, dev->name,
>  				  dev);
> +		}
> +
> +		else	{

Please use kernel coding style: "} 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);
> +		}

I think there's no need to have nested else branches, what about this
approach?

--- a/drivers/net/can/m_can/m_can.c
+++ b/drivers/net/can/m_can/m_can.c
@@ -1831,9 +1831,11 @@ 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 (dev->irq) {
                 err = request_irq(dev->irq, m_can_isr, IRQF_SHARED, dev->name,
                                   dev);
+        } else {
+                // polling
         }
 
         if (err < 0) {

>  	}
>  
>  	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);

Looks better. Please remove the outer "if (IS_ERR(addr) || irq < 0)" and
move the error checking directly after "addr = devm_platform_ioremap_resource_byname()".

What do you think about introducing the "poll-interval" property and
only enable polling if it is set?

>  	}
>  
>  	/* message ram could be shared */
> -- 
> 2.17.1
> 
>

regards,
Marc

-- 
Pengutronix e.K.                 | Marc Kleine-Budde          |
Embedded Linux                   | https://www.pengutronix.de |
Vertretung Nürnberg              | Phone: +49-5121-206917-129 |
Amtsgericht Hildesheim, HRA 2686 | Fax:   +49-5121-206917-9   |

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