linux-kernel - Re: [PATCH v2] backlight: qcom-wled: fix unbalanced ovp irq enable

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Message-ID: <aQC5vsJzeA-cPdKd@aspen.lan>
Date: Tue, 28 Oct 2025 12:40:30 +0000
From: Daniel Thompson <danielt@...nel.org>
To: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
Cc: foss@...lselvaraj.com, Lee Jones <lee@...nel.org>,
	Jingoo Han <jingoohan1@...il.com>, Helge Deller <deller@....de>,
	linux-arm-msm@...r.kernel.org, dri-devel@...ts.freedesktop.org,
	linux-fbdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] backlight: qcom-wled: fix unbalanced ovp irq enable

On Wed, Oct 22, 2025 at 07:14:32PM +0200, Konrad Dybcio wrote:
> On 10/21/25 8:53 PM, Joel Selvaraj via B4 Relay wrote:
> > From: Joel Selvaraj <foss@...lselvaraj.com>
> >
> > In Xiaomi Poco F1 and at least few other devices, the qcom wled driver
> > triggers unbalanced ovp irq enable warning like the following during
> > boot up.
> >
> > [    1.151677] ------------[ cut here ]------------
> > [    1.151680] Unbalanced enable for IRQ 176
> > [    1.151693] WARNING: CPU: 0 PID: 160 at kernel/irq/manage.c:774 __enable_irq+0x50/0x80
> > [    1.151710] Modules linked in:
> > [    1.151717] CPU: 0 PID: 160 Comm: kworker/0:11 Not tainted 5.17.0-sdm845 #4
> > [    1.151724] Hardware name: Xiaomi Pocophone F1 (DT)
> > [    1.151728] Workqueue: events wled_ovp_work
> > ...<snip>...
> > [    1.151833] Call trace:
> > [    1.151836]  __enable_irq+0x50/0x80
> > [    1.151841]  enable_irq+0x48/0xa0
> > [    1.151846]  wled_ovp_work+0x18/0x24
> > [    1.151850]  process_one_work+0x1d0/0x350
> > [    1.151858]  worker_thread+0x13c/0x460
> > [    1.151862]  kthread+0x110/0x114
> > [    1.151868]  ret_from_fork+0x10/0x20
> > [    1.151876] ---[ end trace 0000000000000000 ]---
> >
> > Fix it by storing and checking the state of ovp irq before enabling and
> > disabling it.
> >
> > Signed-off-by: Joel Selvaraj <foss@...lselvaraj.com>
> > ---
> > I was able to debug the issue a little further. This happens mainly because
> > devm_request_threaded_irq already enables the ovp irq during probe. Then ovp
> > work gets scheduled when update_status happens and in turn enables the irq again.
> > Tracking the status makes it easy to avoid the double irq enable. But I am
> > open to try a different approach if there is any suggestion.
>
> Would reverting this change and adding (| IRQF_NO_AUTOEN) to that call
> fix it?

I'd definitely favour trying an alternative approach.

wled_[disable|enable]_ovp_irq() do hide "unbalanced enable/disable"
warnings but they will not nest correctly. That put things are high risk
of bugs (even if there are no bugs now it makes maintaining this driver
"high risk" in the future).


Daniel.