linux-kernel - Re: [PATCH v2 2/7] usb: cdns3-ti: remove runtime PM

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Date:   Wed, 22 Nov 2023 15:42:56 -0800
From:   Kevin Hilman <khilman@...nel.org>
To:     Théo Lebrun <theo.lebrun@...tlin.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Roger Quadros <rogerq@...nel.org>,
        Peter Chen <peter.chen@...nel.org>,
        Pawel Laszczak <pawell@...ence.com>,
        Nishanth Menon <nm@...com>,
        Vignesh Raghavendra <vigneshr@...com>,
        Tero Kristo <kristo@...nel.org>
Cc:     linux-usb@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        Grégory Clement <gregory.clement@...tlin.com>,
        Théo Lebrun <theo.lebrun@...tlin.com>
Subject: Re: [PATCH v2 2/7] usb: cdns3-ti: remove runtime PM

Théo Lebrun <theo.lebrun@...tlin.com> writes:

> The driver does not use RPM. It enables it & gets a reference at probe.
> It then undoes that on probe error or at remove.

...which is a fairly standard thing to do for a rudimentary runtime PM
support on platforms that use power domains.

This will likely (almost surely) break other platforms.

Without a runtime PM get call, the power domain that this device is in
could be powered off without this driver ever knowing about it, causing
a crash as soon as the driver is used after the domain is turned off.

Kevin