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

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Message-ID: <20230522-manhunt-smooth-442d9d864f04-mkl@pengutronix.de>
Date:   Mon, 22 May 2023 20:37:45 +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 22.05.2023 10:17:38, Judith Mendez wrote:
> > > 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;
> > }
> 
> Ok.
> 
> > 
> > > +	irq = platform_get_irq_byname_optional(pdev, "int0");
> > 
> > Remove the "_optional" and....
> 
> On V2, you asked to add the _optional?.....
> 
> >  	irq = platform_get_irq_byname(pdev, "int0");
> 
> use platform_get_irq_byname_optional(), it doesn't print an error
> message.

ACK - I said that back in v2, when there was "poll-interval". But now we
don't use "poll-interval" anymore, but test if interrupt properties are
present.

See again pseudo-code I posted in my last mail:

| if (device_property_present("interrupts") {
|          platform_get_irq_byname();

If this throws an error, it's fatal, bail out.

|          polling = false;
| } else {
|          hrtimer_init();
|          polling = true;
| }


> 
> > 
> > > +	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
> 
> ok,
> 
> > 
> > > +	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.
> 
> Should we not go to 'probe fail' if polling is not activated and irq is not
> found?

If an interrupt property is present in the DT, we use it - if request
IRQ fails, something is broken and we've already bailed out. See above.
If there is no interrupt property we use polling.

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

ACK, this is not possible anymore - we cannot have polling enabled and
HW IRQs configured.

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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