linux-kernel - Re: [PATCH v1 1/2] driver core: fw_devlink: Add support for FWNODE_FLAG_BROKEN

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Date:   Fri, 27 Aug 2021 03:23:01 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Saravana Kannan <saravanak@...gle.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Vladimir Oltean <olteanv@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, Len Brown <lenb@...nel.org>,
        Alvin Sipraga <ALSI@...g-olufsen.dk>, kernel-team@...roid.com,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        linux-acpi@...r.kernel.org
Subject: Re: [PATCH v1 1/2] driver core: fw_devlink: Add support for
 FWNODE_FLAG_BROKEN_PARENT

> Doesn't add much to the discussion. In the example I gave, the driver
> already does synchronous probing. If the device can't probe
> successfully because a supplier isn't ready, it doesn't matter if it's
> a synchronous probe. The probe would still be deferred and we'll hit
> the same issue. Even in the situation the commit [5] describes, if
> parallelized probing is done and the PHY depended on something (say a
> clock), you'd still end up not probing the PHY even if the driver is
> present and the generic PHY would end up force probing it.

genphy is meant to be used when there is no other driver available.
It is a best effort, better than nothing, might work. And quite a few
boards rely on it. However, it should not be used when there is a
specific driver.

So if the PHY device has been probed, and -EPROBE_DEFER was returned,
we also need to return -EPROBE_DEFER here when deciding if genphy
should be used. It should then all unwind and try again later.

I don't know the device core, but it looks like dev->can_match tells
us what we need to know. If true, we know there is a driver for this
device. But i'm hesitant to make use of this outside of driver/base.

	Andrew