Re: (EXT) [PATCH] i2c: imx: add irqf_no_suspend

From: Wolfram Sang <wsa@kernel.org>
To: Alexander Stein <alexander.stein@ew.tq-group.com>
Cc: Alifer Moraes <alifer.m@variscite.com>,
	linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org, eran.m@variscite.com,
	festevam@gmail.com, kernel@pengutronix.de, linux-imx@nxp.com,
	linux-i2c@vger.kernel.org, linux@rempel-privat.de,
	pierluigi.p@variscite.com, s.hauer@pengutronix.de,
	shawnguo@kernel.org, gaopan <b54642@freescale.com>,
	Fugang Duan <B38611@freescale.com>,
	Vipul Kumar <vipul_kumar@mentor.com>
Subject: Re: (EXT) [PATCH] i2c: imx: add irqf_no_suspend
Date: Sat, 21 May 2022 12:24:16 +0200	[thread overview]
Message-ID: <Yoi90G5cphagcxpp@shikoro> (raw)
In-Reply-To: <3676803.kQq0lBPeGt@steina-w>

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Hi everyone,

> > The i2c irq is masked when pcie starts a i2c transfer process
> > during noirq suspend stage. As a result, i2c transfer fails.
> > To solve the problem, IRQF_NO_SUSPEND is added to i2c bus.
> > 
> > Signed-off-by: Gao Pan <b54642@freescale.com>
> > Signed-off-by: Fugang Duan <B38611@freescale.com>
> > Signed-off-by: Vipul Kumar <vipul_kumar@mentor.com>

The SoB from Alifer Moraes is missing, too.

> > goto rpm_disable;
> > 
> >  	/* Request IRQ */
> > -	ret = request_threaded_irq(irq, i2c_imx_isr, NULL, IRQF_SHARED,
> > +	ret = request_threaded_irq(irq, i2c_imx_isr, NULL,
> > +				   IRQF_SHARED | IRQF_NO_SUSPEND,
> >  				   pdev->name, i2c_imx);
> >  	if (ret) {
> >  		dev_err(&pdev->dev, "can't claim irq %d\n", irq);
> 
> 
> I stumbled across Documentation/power/suspend-and-interrupts.rst which states:
> > For this reason, using IRQF_NO_SUSPEND and IRQF_SHARED at the
> > same time should be avoided.
> Given this IMHO at least a comment should be inserted why this is fine. I dont 
> have a full picture about the situation, but to me it seems there is a 
> reference missing, or why/how does some PCIe start some I2C transfer when the
> controller is suspended already? Do I miss something?

Thank you for this comment, Alexander. I second you, this needs
explanation.

Happy hacking,

   Wolfram

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