linux-kernel - Re: [PATCH] phy: work around 'phys' references to usb-phy devices

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Message-ID: <CAK8P3a0NSGCR8=MzHAPqyhWMsUWAxJjtstYo8gszKcXUCaupgg@mail.gmail.com>
Date:   Thu, 11 Jan 2018 16:20:53 +0100
From:   Arnd Bergmann <arnd@...db.de>
To:     Kishon Vijay Abraham I <kishon@...com>
Cc:     Eric Anholt <eric@...olt.net>,
        Florian Fainelli <f.fainelli@...il.com>,
        DTML <devicetree@...r.kernel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Rob Herring <robh+dt@...nel.org>, linux-usb@...r.kernel.org,
        "# 3.4.x" <stable@...r.kernel.org>,
        Stefan Wahren <stefan.wahren@...e.com>,
        Felipe Balbi <balbi@...nel.org>,
        Andrzej Pietrasiewicz <andrzej.p@...sung.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] phy: work around 'phys' references to usb-phy devices

On Thu, Jan 11, 2018 at 2:30 PM, Kishon Vijay Abraham I <kishon@...com> wrote:
> On Thursday 11 January 2018 02:27 AM, Arnd Bergmann wrote:
>> On Mon, Jan 8, 2018 at 7:32 PM, Kishon Vijay Abraham I <kishon@...com> wrote:
>>> On Monday 08 January 2018 06:31 PM, Arnd Bergmann wrote:
>>>> Stefan Wahren reports a problem with a warning fix that was merged
>>>> ---
>>>> This obviously needs to be tested, I wrote this up as a reply to
>>>> Stefan's bug report. I'm fairly sure that I covered all usb-phy
>>>> driver strings here. My goal is to have a fix merged into 4.15
>>>> rather than reverting all the DT fixes.
>>>
>>> Shouldn't the fix be in phy consumer drivers to not return error if it's able
>>> to find the phy either using usb-phy or generic phy?
>>
>> Stefan has posted a patch to that effect now, but I fear that might be
>> a little fragile, in particular this short before the release with the
>> regression
>> in place.
>>
>> The main problem is that we'd have to change the generic
>> usb_add_hcd() function in addition to dwc2 and dwc3 to ignore
>> -EPROBE_DEFER from phy_get() whenever usb_get_phy_dev()
>> has already succeeded.
>>
>> If there is any HCD that relies on usb_add_hcd() to get both the
>> usb_phy and the phy structures, and it may need to defer probing
>> when the latter one isn't ready yet, that fix would break another
>> driver.
>
> hmm.. IMO the better thing right now would be to revert the dt patch which adds
> #phy-cells.
> We have to see if there are better fixes in order to add #phy-cells warning fix
> in stable tree.

Let's see which patches that would be, I think this is the full list of
nodes that got an extra #phy-cells:

c22fe696157d ARM: dts: Fix dm814x missing phy-cells property
f0e11ff8ff65 ARM: dts: am33xx: Add missing #phy-cells to ti,am335x-usb-phy
c5bbf358b790 arm: dts: nspire: Add missing #phy-cells to usb-nop-xceiv
44e5dced2ef6 arm: dts: marvell: Add missing #phy-cells to usb-nop-xceiv
014d6da6cb25 ARM: dts: bcm283x: Fix DTC warnings about missing phy-cells
f568f6f554b8 ARM: dts: omap: Add missing #phy-cells to usb-nop-xceiv

plus a couple in linux-next:

d745d5f277bf ARM: dts: imx51-zii-rdu1: Add missing #phy-cells to usb-nop-xceiv
915fbe59cbf2 ARM: dts: imx: Add missing #phy-cells to usb-nop-xceiv

It's a lot of patches to revert, and I guess it would get us back to hundreds
of warnings in an allmodconfig build, so I'd first try to come up with
ways to prove that at least some of them can stay.

Almost all the warnings are about "usb-nop-xceiv" phys, the only exceptions
I could find are the OMAP ones (the first two patches), which use
"ti,am335x-usb-phy" and are referenced from a "ti,musb-am33xx". That
particular driver is not affected by the bug, so we can leave that in.

To deal with all the "usb-nop-xceiv"  references including the one that
Stefan reported, we could use a much simpler version of my earlier
patch, do you think this is any better?

Signed-off-by: Arnd Bergmann <arnd@...db.de>

diff --git a/drivers/phy/phy-core.c b/drivers/phy/phy-core.c
index b4964b067aec..f056d8fb3921 100644
--- a/drivers/phy/phy-core.c
+++ b/drivers/phy/phy-core.c
@@ -410,6 +410,10 @@ static struct phy *_of_phy_get(struct device_node
*np, int index)
        if (ret)
                return ERR_PTR(-ENODEV);

+       /* This phy type handled by the usb-phy subsystem for now */
+       if (of_device_is_compatible("usb-nop-xceiv"))
+               return ERR_PTR(-ENODEV);
+
        mutex_lock(&phy_provider_mutex);
        phy_provider = of_phy_provider_lookup(args.np);
        if (IS_ERR(phy_provider) || !try_module_get(phy_provider->owner)) {