linux-kernel - Re: [PATCH v1 3/3] usb: typec: fusb302: Switch to threaded interrupt handler

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Message-ID: <080d9ed6-18f9-437e-89d4-aba8f69120fb@kernel.org>
Date: Wed, 7 Jan 2026 11:52:44 +0100
From: Hans de Goede <hansg@...nel.org>
To: 张永波 <giraffesnn123@...il.com>
Cc: Anand Moon <linux.amoon@...il.com>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
 <conor+dt@...nel.org>, Heiko Stuebner <heiko@...ech.de>,
 Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 Sebastian Reichel <sebastian.reichel@...labora.com>,
 FUKAUMI Naoki <naoki@...xa.com>,
 Nicolas Frattaroli <nicolas.frattaroli@...labora.com>,
 Cristian Ciocaltea <cristian.ciocaltea@...labora.com>,
 "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS"
 <devicetree@...r.kernel.org>,
 "moderated list:ARM/Rockchip SoC support"
 <linux-arm-kernel@...ts.infradead.org>,
 "open list:ARM/Rockchip SoC support" <linux-rockchip@...ts.infradead.org>,
 open list <linux-kernel@...r.kernel.org>,
 "open list:USB TYPEC CLASS" <linux-usb@...r.kernel.org>
Subject: Re: [PATCH v1 3/3] usb: typec: fusb302: Switch to threaded interrupt
 handler

Hi,

On 7-Jan-26 10:52, 张永波 wrote:
>> Still ideally we would solve this in another way then
>> switching to a threaded IRQ handler.
>>
>> As the commit message of the mei-vsc fix mentions
>> the root cause of these errors is typically an interrupt
>> chip driver which uses IRQF_NO_THREAD disabling the auto
>> threading of all interrupt handlers in RT mode.
>>
>> So the first question here would be to see if that flag is
>> used in the interrupt chip and if yes, is that flag really
>> necessary ?
> This is very similar to the issue addressed in commit 24b176d8827d
> ("drm/msm/dsi: Remove spurious IRQF_ONESHOT flag").
> The IRQF_ONESHOT flag is preventing forced threading here.
> 
> In irq_setup_forced_threading(), the conversion to threaded interrupts
> is explicitly skipped if any of the IRQF_NO_THREAD, IRQF_PERCPU,
> or IRQF_ONESHOT flags are present. In this case, IRQF_ONESHOT
> appears to be the reason.

Ah, well the code effectively does its own IRQF_ONESHOT handling,
since it needs to do its own threaded-irq like handling for
suspend/resume reasons. It disables the IRQ when it fires and
then only re-enables it once the work has done processing the IRQ.

So it should be perfectly safe to drop the IRQF_ONESHOT flag.

If that also works to resolve the lockdep issue that would be
the preferred way of fixing this IMHO.

Regards,

Hans