linux-kernel - Re: [PATCH v6 2/2] can: m_can: Add hrtimer to generate software interrupt

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Message-ID: <20230519-morbidity-directory-dbe704584aa3-mkl@pengutronix.de>
Date:   Fri, 19 May 2023 09:16:43 +0200
From:   Marc Kleine-Budde <mkl@...gutronix.de>
To:     Judith Mendez <jm@...com>
Cc:     Chandrasekar Ramakrishnan <rcsekar@...sung.com>,
        linux-can@...r.kernel.org, Wolfgang Grandegger <wg@...ndegger.com>,
        "David S . Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, Schuyler Patton <spatton@...com>,
        Tero Kristo <kristo@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org,
        Oliver Hartkopp <socketcan@...tkopp.net>,
        Conor Dooley <conor+dt@...nel.org>
Subject: Re: [PATCH v6 2/2] can: m_can: Add hrtimer to generate software
 interrupt

On 18.05.2023 14:36:13, 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@...com>

[...]

> 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;
>  	}
>  

As we don't use an explicit "poll-interval" anymore, this needs some
cleanup. The flow should be (pseudo code, error handling omitted):

if (device_property_present("interrupts") {
        platform_get_irq_byname();
        polling = false;
} else {
        hrtimer_init();
        polling = true;
}

> +	irq = platform_get_irq_byname_optional(pdev, "int0");

Remove the "_optional" and....

> +	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;

...move the platform_get_irq_byname() here

> +	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;
> +	}

Remove this check.

> +
> +	if (mcan_class->polling) {
> +		if (irq > 0) {
> +			mcan_class->polling = false;
> +			dev_info(mcan_class->dev, "Polling enabled, using hardware IRQ\n");

Remove this.

> +		} else {
> +			dev_dbg(mcan_class->dev, "Polling enabled, initialize hrtimer");
> +			hrtimer_init(&mcan_class->hrtimer, CLOCK_MONOTONIC,
> +				     HRTIMER_MODE_REL_PINNED);

move this backwards, where you set "polling = true"

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

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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