linux-kernel - Re: [PATCH v3] PCI: Prevent power state transition of erroneous device

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Message-ID: <aCLNe2wHTiKdE5ZO@wunner.de>
Date: Tue, 13 May 2025 06:41:31 +0200
From: Lukas Wunner <lukas@...ner.de>
To: Raag Jadav <raag.jadav@...el.com>
Cc: rafael@...nel.org, mahesh@...ux.ibm.com, oohall@...il.com,
	bhelgaas@...gle.com, linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org, ilpo.jarvinen@...ux.intel.com,
	aravind.iddamsetty@...ux.intel.com
Subject: Re: [PATCH v3] PCI: Prevent power state transition of erroneous
 device

On Sun, May 04, 2025 at 02:34:44PM +0530, Raag Jadav wrote:
> If error flags are set on an AER capable device, most likely either the
> device recovery is in progress or has already failed. Neither of the
> cases are well suited for power state transition of the device, since
> this can lead to unpredictable consequences like resume failure, or in
> worst case the device is lost because of it. Leave the device in its
> existing power state to avoid such issues.

Have you witnessed this on a particular platform / hardware combination?
If so, it would be good to mention it.  If I'd happen to find this
commit in the future through "git blame", that's the first question
that would come to mind:  How and on what hardware was this actually
triggered, how can I reproduce it.

> +	/*
> +	 * If error flags are set on an AER capable device, most likely either
> +	 * the device recovery is in progress or has already failed. Neither of
> +	 * the cases are well suited for power state transition of the device,
> +	 * since this can lead to unpredictable consequences like resume
> +	 * failure, or in worst case the device is lost because of it. Leave the
> +	 * device in its existing power state to avoid such issues.
> +	 */

That's quite verbose and merely a 1:1 repetition of the commit message.
I'd recommend a more condensed code comment and anyone interested in
further details may look them up in the commit message.

Thanks,

Lukas