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From:   Pierluigi Passaro <pierluigi.p@variscite.com>
To:     Wolfram Sang <wsa@kernel.org>,
        Alexander Stein <alexander.stein@ew.tq-group.com>
CC:     Alifer Willians de Moraes <alifer.m@variscite.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-arm-kernel@lists.infradead.org" 
        <linux-arm-kernel@lists.infradead.org>,
        Eran Matityahu <eran.m@variscite.com>,
        "festevam@gmail.com" <festevam@gmail.com>,
        "kernel@pengutronix.de" <kernel@pengutronix.de>,
        "linux-imx@nxp.com" <linux-imx@nxp.com>,
        "linux-i2c@vger.kernel.org" <linux-i2c@vger.kernel.org>,
        "linux@rempel-privat.de" <linux@rempel-privat.de>,
        "s.hauer@pengutronix.de" <s.hauer@pengutronix.de>,
        "shawnguo@kernel.org" <shawnguo@kernel.org>,
        gaopan <b54642@freescale.com>,
        Fugang Duan <B38611@freescale.com>,
        Vipul Kumar <vipul_kumar@mentor.com>
Subject: Re: [PATCH] i2c: imx: add irqf_no_suspend
Thread-Topic: [PATCH] i2c: imx: add irqf_no_suspend
Thread-Index: AQHYhKbNy8DyxLOJYkqA++Q1ekhxAQ==
Date:   Mon, 20 Jun 2022 13:29:30 +0000
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Hi All,=0A=
=0A=
> Hi everyone,=0A=
=0A=
> > > The i2c irq is masked when pcie starts a i2c transfer process=0A=
> > > during noirq suspend stage. As a result, i2c transfer fails.=0A=
> > > To solve the problem, IRQF_NO_SUSPEND is added to i2c bus.=0A=
> > > =0A=
> > > Signed-off-by: Gao Pan <b54642@freescale.com>=0A=
> > > Signed-off-by: Fugang Duan <B38611@freescale.com>=0A=
> > > Signed-off-by: Vipul Kumar <vipul_kumar@mentor.com>=0A=
=0A=
> The SoB from Alifer Moraes is missing, too.=0A=
=0A=
> > > goto rpm_disable;=0A=
> > > =0A=
> > >=A0=A0=A0=A0=A0 /* Request IRQ */=0A=
> > > -=A0=A0 ret =3D request_threaded_irq(irq, i2c_imx_isr, NULL, IRQF_SHA=
RED,=0A=
> > > +=A0=A0 ret =3D request_threaded_irq(irq, i2c_imx_isr, NULL,=0A=
> > > +=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=
=A0=A0=A0=A0=A0=A0=A0 IRQF_SHARED | IRQF_NO_SUSPEND,=0A=
> > >=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=
=A0=A0=A0=A0=A0=A0=A0=A0=A0 pdev->name, i2c_imx);=0A=
> > >=A0=A0=A0=A0=A0 if (ret) {=0A=
> > >=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 dev_err(&pdev->dev, "can't cla=
im irq %d\n", irq);=0A=
> > =0A=
> > =0A=
> > I stumbled across Documentation/power/suspend-and-interrupts.rst which =
states:=0A=
> > > For this reason, using IRQF_NO_SUSPEND and IRQF_SHARED at the=0A=
> > > same time should be avoided.=0A=
> > Given this IMHO at least a comment should be inserted why this is fine.=
 I dont =0A=
> > have a full picture about the situation, but to me it seems there is a =
=0A=
> > reference missing, or why/how does some PCIe start some I2C transfer wh=
en the=0A=
> > controller is suspended already? Do I miss something?=0A=
=0A=
This patch has been introduced to fix the following behavior.=0A=
HW conditions=0A=
- Variscite DART-MX8M on DT8MCustomBoard v2.x or higher.=0A=
- The PCIe connector uses a reset pin coming from a GPIO expander connected=
 to the I2C bus.=0A=
SW behavior=0A=
- Upon wake-up, the PCIe try toggling the reset pins, but the GPIO expander=
 / I2C bus are still suspended, leading to a PCIe wake-up failure.=0A=
From our investigation, we can't identify a way to postpone PCIe wake-up af=
ter I2C wake-up.=0A=
This patch is still present in latest NXP kernel 5.15, but please let me kn=
ow if you think this should be approached / fixed in a different way.=0A=
=0A=
Thanks=0A=
Regards=0A=
Pier=0A=
=0A=
=0A=
> Thank you for this comment, Alexander. I second you, this needs=0A=
> explanation.=0A=
=0A=
> Happy hacking,=0A=
>   Wolfram=0A=