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Date:   Wed, 14 Jun 2023 09:02:56 +0200
From:   Marc Kleine-Budde <mkl@pengutronix.de>
To:     Judith Mendez <jm@ti.com>
Cc:     Chandrasekar Ramakrishnan <rcsekar@samsung.com>,
        linux-can@vger.kernel.org, Wolfgang Grandegger <wg@grandegger.com>,
        "David S . Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org, Schuyler Patton <spatton@ti.com>,
        Tero Kristo <kristo@kernel.org>,
        Rob Herring <robh+dt@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        devicetree@vger.kernel.org,
        Oliver Hartkopp <socketcan@hartkopp.net>,
        Simon Horman <simon.horman@corigine.com>,
        Conor Dooley <conor+dt@linaro.org>,
        Tony Lindgren <tony@atomide.com>
Subject: Re: [PATCH v8 2/2] can: m_can: Add hrtimer to generate software
 interrupt
Message-ID: <20230614-creasing-moneybags-c7a9654b72b9-mkl@pengutronix.de>
References: <20230530224820.303619-1-jm@ti.com>
 <20230530224820.303619-3-jm@ti.com>
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On 30.05.2023 17:48:20, Judith Mendez wrote:
> 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.
>=20
> On AM62x SoC, MCANs on MCU domain do not have hardware interrupt
> routed to A53 Linux, instead they will use timer polling method.
>=20
> 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.
>=20
> Signed-off-by: Judith Mendez <jm@ti.com>
> ---
> Changelog:
> v8:
> - Cancel hrtimer after interrupts in m_can_stop
> - Move assignment of hrtimer_callback to m_can_class_register()
> - Initialize irq =3D 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=20
> - 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(-)
>=20
> 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)
> =20
> +/* Hrtimer polling interval */
> +#define HRTIMER_POLL_INTERVAL		1

Please add _MS to the macro name.

> +
>  /* 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)
> =20
>  	m_can_enable_all_interrupts(cdev);
> =20
> +	if (dev->irq =3D=3D 0) {

        if (!dev->irq) {

> +		dev_dbg(cdev->dev, "Start hrtimer\n");
> +		hrtimer_start(&cdev->hrtimer, ms_to_ktime(HRTIMER_POLL_INTERVAL),
> +			      HRTIMER_MODE_REL_PINNED);
> +	}
> +
>  	return 0;
>  }
> =20
> @@ -1568,6 +1578,11 @@ static void m_can_stop(struct net_device *dev)
>  {
>  	struct m_can_classdev *cdev =3D netdev_priv(dev);
> =20
> +	if (dev->irq =3D=3D 0) {

        if (!dev->irq) {

> +		dev_dbg(cdev->dev, "Stop hrtimer\n");
> +		hrtimer_cancel(&cdev->hrtimer);
> +	}
> +
>  	/* disable all interrupts */
>  	m_can_disable_all_interrupts(cdev);
> =20
> @@ -1793,6 +1808,18 @@ static netdev_tx_t m_can_start_xmit(struct sk_buff=
 *skb,
>  	return NETDEV_TX_OK;
>  }
> =20
> +static enum hrtimer_restart hrtimer_callback(struct hrtimer *timer)
> +{
> +	struct m_can_classdev *cdev =3D 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 =3D netdev_priv(dev);
> @@ -1831,10 +1858,10 @@ static int m_can_open(struct net_device *dev)
>  		err =3D request_threaded_irq(dev->irq, NULL, m_can_isr,
>  					   IRQF_ONESHOT,
>  					   dev->name, dev);
> -	} else {
> +	}
> +	if (dev->irq > 0)

I think you broke the peripheral case. Should be:

        } else if (dev->irq) {
                ...
        }

>  		err =3D request_irq(dev->irq, m_can_isr, IRQF_SHARED, dev->name,
>  				  dev);
> -	}
> =20
>  	if (err < 0) {
>  		netdev_err(dev, "failed to request interrupt\n");
> @@ -2027,6 +2054,9 @@ int m_can_class_register(struct m_can_classdev *cde=
v)
>  			goto clk_disable;
>  	}
> =20
> +	if (cdev->net->irq =3D=3D 0)

        if (!cdev->net->irq)

> +		cdev->hrtimer.function =3D &hrtimer_callback;
> +
>  	ret =3D 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;
> =20
>  	struct mram_cfg mcfg[MRAM_CFG_NUM];
> +
> +	struct hrtimer hrtimer;
>  };
> =20
>  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_c=
an/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/
> =20
> +#include <linux/hrtimer.h>
>  #include <linux/phy/phy.h>
>  #include <linux/platform_device.h>
> =20
> @@ -96,12 +97,29 @@ static int m_can_plat_probe(struct platform_device *p=
dev)
>  		goto probe_fail;
> =20
>  	addr =3D devm_platform_ioremap_resource_byname(pdev, "m_can");
> -	irq =3D platform_get_irq_byname(pdev, "int0");
> -	if (IS_ERR(addr) || irq < 0) {
> -		ret =3D -EINVAL;
> +	if (IS_ERR(addr)) {
> +		ret =3D PTR_ERR(addr);
>  		goto probe_fail;
>  	}
> =20
> +	if (device_property_present(mcan_class->dev, "interrupts") ||
> +	    device_property_present(mcan_class->dev, "interrupt-names")) {
> +		irq =3D platform_get_irq_byname(pdev, "int0");
> +		if (irq =3D=3D -EPROBE_DEFER) {
> +			ret =3D -EPROBE_DEFER;
> +			goto probe_fail;
> +		}
> +		if (irq < 0) {
> +			ret =3D -EINVAL;

please return the original error value.

> +			goto probe_fail;
> +		}
> +	} else {
> +		irq =3D 0;

Please initialize irq as 0 during declaration.

> +		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 =3D platform_get_resource_byname(pdev, IORESOURCE_MEM, "message_ram=
");
>  	if (!res) {
> --=20
> 2.34.1
>=20
>=20

regards,
Marc

--=20
Pengutronix e.K.                 | Marc Kleine-Budde          |
Embedded Linux                   | https://www.pengutronix.de |
Vertretung N=C3=BCrnberg              | Phone: +49-5121-206917-129 |
Amtsgericht Hildesheim, HRA 2686 | Fax:   +49-5121-206917-9   |

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