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

From: Alexander Stein <alexander.stein@ew.tq-group.com>
To: Alifer Moraes <alifer.m@variscite.com>
Cc: linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org, eran.m@variscite.com,
	festevam@gmail.com, kernel@pengutronix.de,
	linux-arm-kernel@lists.infradead.org, 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: Fri, 11 Mar 2022 11:57:48 +0100	[thread overview]
Message-ID: <3676803.kQq0lBPeGt@steina-w> (raw)
In-Reply-To: <20220307143630.28697-1-alifer.m@variscite.com>

Hallo,

Am Montag, 7. März 2022, 15:36:30 CET schrieb Alifer Moraes:
> From: gaopan <b54642@freescale.com>
> 
> 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>
> ---
>  drivers/i2c/busses/i2c-imx.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/i2c/busses/i2c-imx.c b/drivers/i2c/busses/i2c-imx.c
> index 27f969b3dc07..fcc09a1e7f44 100644
> --- a/drivers/i2c/busses/i2c-imx.c
> +++ b/drivers/i2c/busses/i2c-imx.c
> @@ -1478,7 +1478,8 @@ static int i2c_imx_probe(struct platform_device *pdev)
> 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?

Best regards,
Alexander