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From:   Saravana Kannan <saravanak@google.com>
Date:   Sun, 31 Jan 2021 13:37:45 -0800
Message-ID: <CAGETcx9Qg5cwMckeqxUCrf+e4d49Ph-yPYPfHMzUQLYR9jsdNw@mail.gmail.com>
Subject: Re: [PATCH v1 0/2] Make fw_devlink=on more forgiving
To:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        "Rafael J. Wysocki" <rafael@kernel.org>,
        Marek Szyprowski <m.szyprowski@samsung.com>,
        Geert Uytterhoeven <geert@linux-m68k.org>,
        Marc Zyngier <maz@kernel.org>,
        Tudor Ambarus <Tudor.Ambarus@microchip.com>,
        Linus Walleij <linus.walleij@linaro.org>,
        Bartosz Golaszewski <bgolaszewski@baylibre.com>
Cc:     LKML <linux-kernel@vger.kernel.org>,
        Android Kernel Team <kernel-team@android.com>
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On Fri, Jan 29, 2021 at 8:03 PM Saravana Kannan <saravanak@google.com> wrote:
>
> This patch series solves two general issues with fw_devlink=on
>
> Patch 1/2 addresses the issue of firmware nodes that look like they'll
> have struct devices created for them, but will never actually have
> struct devices added for them. For example, DT nodes with a compatible
> property that don't have devices added for them.
>
> Patch 2/2 address (for static kernels) the issue of optional suppliers
> that'll never have a driver registered for them. So, if the device could
> have probed with fw_devlink=permissive with a static kernel, this patch
> should allow those devices to probe with a fw_devlink=on. This doesn't
> solve it for the case where modules are enabled because there's no way
> to tell if a driver will never be registered or it's just about to be
> registered. I have some other ideas for that, but it'll have to come
> later thinking about it a bit.
>
> These two patches might remove the need for several other patches that
> went in as fixes for commit e590474768f1 ("driver core: Set
> fw_devlink=on by default"), but I think all those fixes are good
> changes. So I think we should leave those in.
>
> Marek, Geert,
>
> Can you try this series on a static kernel with your OF_POPULATED
> changes reverted? I just want to make sure these patches can identify
> and fix those cases.
>
> Tudor,
>
> You should still make the clock driver fix (because it's a bug), but I
> think this series will fix your issue too (even without the clock driver
> fix). Can you please give this a shot?
>
> Marc,
>
> Can you try this series with the gpiolib fix reverted please? I'm pretty
> sure this will fix that case.
>
> Linus,
>
> This series very likely removes the need for the gpiolib patch (we can
> wait for Marc to confirm). I'm split on whether we should leave it in or
> not. Thoughts?

Actually, thinking more about this, we should keep the gpiolib patch.
It'll ensure the suspend/resume order is always correct.

This series basically gives up on creating device links to firmware
nodes that don't have a corresponding device added. The gpiolib patch
makes sure the nodes have a device that corresponds to them. So device
links will get created to the gpio_device and will make sure the
parent of the gpio_device doesn't suspend before the consumers of the
gpio.

-Saravana