linux-kernel - Re: [PATCH 1/3] remoteproc: qcom_q6v5: Avoid disabling handover IRQ twice

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Message-ID: <aKSQTc5u5AePWVwj@linaro.org>
Date: Tue, 19 Aug 2025 16:55:09 +0200
From: Stephan Gerhold <stephan.gerhold@...aro.org>
To: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
Cc: Bjorn Andersson <andersson@...nel.org>,
	Mathieu Poirier <mathieu.poirier@...aro.org>,
	Sibi Sankar <quic_sibis@...cinc.com>,
	Abel Vesa <abel.vesa@...aro.org>, linux-arm-msm@...r.kernel.org,
	linux-remoteproc@...r.kernel.org, linux-kernel@...r.kernel.org,
	Konrad Dybcio <konradybcio@...nel.org>
Subject: Re: [PATCH 1/3] remoteproc: qcom_q6v5: Avoid disabling handover IRQ
 twice

On Tue, Aug 19, 2025 at 02:44:26PM +0300, Dmitry Baryshkov wrote:
> On Tue, Aug 19, 2025 at 01:08:02PM +0200, Stephan Gerhold wrote:
> > enable_irq() and disable_irq() are reference counted, so we must make sure
> > that each enable_irq() is always paired with a single disable_irq(). If we
> > call disable_irq() twice followed by just a single enable_irq(), the IRQ
> > will remain disabled forever.
> > 
> > For the error handling path in qcom_q6v5_wait_for_start(), disable_irq()
> > will end up being called twice, because disable_irq() also happens in
> > qcom_q6v5_unprepare() when rolling back the call to qcom_q6v5_prepare().
> > 
> > Fix this by dropping disable_irq() in qcom_q6v5_wait_for_start(). Since
> > qcom_q6v5_prepare() is the function that calls enable_irq(), it makes more
> > sense to have the rollback handled always by qcom_q6v5_unprepare().
> > 
> > Fixes: 3b415c8fb263 ("remoteproc: q6v5: Extract common resource handling")
> 
> Didn't earlier versions also have the same behaviour?
> 

I don't think so. The "extracted common resource handling" came from
qcom_q6v5_pil.c, but q6v5_start() just had most of this code inline in a
single function [1]. The handling of enable_irq()/disable_irq() through
the goto labels looks correct there.

Thanks,
Stephan

[1]: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/remoteproc/qcom_q6v5_pil.c?id=0e622e80191e75c99b6ecc265c140a37d81e7a63#n795