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From:   Jason Liu <jason.hui.liu@nxp.com>
To:     Sudeep Holla <sudeep.holla@arm.com>
CC:     "will@kernel.org" <will@kernel.org>,
        "catalin.marinas@arm.com" <catalin.marinas@arm.com>,
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        <linux-arm-kernel@lists.infradead.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: RE: [PATCH 1/1] arm64: kexec: no need to do irq_chip->irq_mask if it
 already masked
Thread-Topic: [PATCH 1/1] arm64: kexec: no need to do irq_chip->irq_mask if it
 already masked
Thread-Index: AQHWaj3ZMAA/XWH8SkmG3qCWNnZEoaknvUCAgAErEuA=
Date:   Wed, 5 Aug 2020 06:30:13 +0000
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 <20200804102025.GA15199@bogus>
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> -----Original Message-----
> From: Sudeep Holla <sudeep.holla@arm.com>
> Sent: Tuesday, August 4, 2020 6:20 PM
> To: Jason Liu <jason.hui.liu@nxp.com>
> Cc: will@kernel.org; catalin.marinas@arm.com; ashal@kernel.org;
> maz@kernel.org; linux-arm-kernel@lists.infradead.org;
> linux-kernel@vger.kernel.org
> Subject: Re: [PATCH 1/1] arm64: kexec: no need to do irq_chip->irq_mask i=
f it
> already masked
>=20
> +Marc Z
>=20
> On Tue, Aug 04, 2020 at 04:56:57PM +0800, Jason Liu wrote:
> > No need to do the irq_chip->irq_mask() if it already masked.
> > BTW, unconditionally do the irq_chip->irq_mask() will also bring
> > issues when the irq_chip in the runtime PM suspend. Accessing
> > registers of the irq_chip will bring in the exceptions. For example on =
the i.MX:
> >
>=20
> The change looks good and is inline with the additional checks we do for =
eoi
> and disable. However, the imx_irqsteer_irq_mask is not safe to be called =
with
> runtime suspend.=20

Yes, you are right. imx_irqsteer_irq_mask can not be called with irqchip ru=
ntime suspend.
IMO, this might apply to all platforms which implement the irq_chip->mask f=
unction with
directly access the registers.

> What happens if some driver using the irq on this chip calls
> disable_irq when this irqchip is suspended ?

IMO, only free_irq will call the irq_chip_pm_put which will bring the irqch=
ip to suspend if that irq is the last user.
Otherwise, the irqchip is in active state. free_irq will set the IRQ state =
to DISABLED and MASKED.
So, if the irqchip in suspend state, which means all the irqs(associated wi=
th irqchip) were DISABLED and MASKED.
If call the common API disable_irq, that is fine due to the disable_irq wil=
l nop if the irq was DISABLED and masked.=20

>=20
> --
> Regards,
> Sudeep