linux-kernel - Re: [PATCH 1/2] i2c: designware: Avoid taking clk

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Message-ID: <aKXyVvFOvpsaAEAB@smile.fi.intel.com>
Date: Wed, 20 Aug 2025 19:05:42 +0300
From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To: Jisheng Zhang <jszhang@...nel.org>
Cc: Jarkko Nikula <jarkko.nikula@...ux.intel.com>,
	Mika Westerberg <mika.westerberg@...ux.intel.com>,
	Jan Dabros <jsd@...ihalf.com>, Andi Shyti <andi.shyti@...nel.org>,
	linux-kernel@...r.kernel.org, linux-i2c@...r.kernel.org
Subject: Re: [PATCH 1/2] i2c: designware: Avoid taking clk_prepare mutex in
 PM callbacks

On Wed, Aug 20, 2025 at 11:31:24PM +0800, Jisheng Zhang wrote:
> This is unsafe, as the runtime PM callbacks are called from the PM
> workqueue, so this may deadlock when handling an i2c attached clock,
> which may already hold the clk_prepare mutex from another context.

Can you be more specific? What is the actual issue in practice?
Do you have traces and lockdep warnings?

AFAICS it seems related to the bus recovery mechanism. Is this what you have in
mind?

-- 
With Best Regards,
Andy Shevchenko