linux-kernel - Re: [RFC PATCH v1] driver core: Set fw_devlink to "permissive" behavior by default

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Message-ID: <CAGETcx9nhF4hjs6BQ21Ees4LJLM7kENj6Ja619Sonjvvt1o7wA@mail.gmail.com>
Date:   Mon, 30 Mar 2020 11:41:25 -0700
From:   Saravana Kannan <saravanak@...gle.com>
To:     Marek Szyprowski <m.szyprowski@...sung.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Frank Rowand <frowand.list@...il.com>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        Android Kernel Team <kernel-team@...roid.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH v1] driver core: Set fw_devlink to "permissive"
 behavior by default

On Sun, Mar 29, 2020 at 11:20 PM Marek Szyprowski
<m.szyprowski@...sung.com> wrote:
>
> Hi
>
> On 2020-03-27 19:30, Saravana Kannan wrote:
> > On Fri, Mar 27, 2020 at 8:21 AM Greg Kroah-Hartman
> > <gregkh@...uxfoundation.org> wrote:
> >> On Fri, Mar 27, 2020 at 11:25:48AM +0100, Marek Szyprowski wrote:
> >>> On 2020-03-21 22:03, Saravana Kannan wrote:
> >>>> Set fw_devlink to "permissive" behavior by default so that device links
> >>>> are automatically created (with DL_FLAG_SYNC_STATE_ONLY) by scanning the
> >>>> firmware.
> >>>>
> >>>> This ensures suppliers get their sync_state() calls only after all their
> >>>> consumers have probed successfully. Without this, suppliers will get
> >>>> their sync_state() calls at late_initcall_sync() even if their consuer
> >>>>
> >>>> Ideally, we'd want to set fw_devlink to "on" or "rpm" by default. But
> >>>> that needs more testing as it's known to break some corner case
> >>>> drivers/platforms.
> >>>>
> >>>> Cc: Rob Herring <robh+dt@...nel.org>
> >>>> Cc: Frank Rowand <frowand.list@...il.com>
> >>>> Cc: devicetree@...r.kernel.org
> >>>> Signed-off-by: Saravana Kannan <saravanak@...gle.com>
> >>> This patch has just landed in linux-next 20200326. Sadly it breaks
> >>> booting of the Raspberry Pi3b and Pi4 boards, either in 32bit or 64bit
> >>> mode. There is no warning nor panic message, just a silent freeze. The
> >>> last message shown on the earlycon is:
> >>>
> >>> [    0.893217] Serial: 8250/16550 driver, 1 ports, IRQ sharing enabled
> > Marek,
> >
> > Any chance you could get me a stack trace for when it's stuck? That'd
> > be super helpful and I'd really appreciate it. Is it working fine on
> > other variants of Raspberry?
>
> I have no access to other variants of Raspberry board.
>
> The issue seems to be related to bcm2835aux_serial_driver. I've added
> "initcall_debug" and "ignore_loglevel" to kernel cmdline and I got the
> following log:
>
> [    4.595353] calling  exar_pci_driver_init+0x0/0x30 @ 1
> [    4.600597] initcall exar_pci_driver_init+0x0/0x30 returned 0 after
> 44 usecs
> [    4.607747] calling  bcm2835aux_serial_driver_init+0x0/0x28 @ 1
>
> The with some debug printk calls I've found that the clock lookup fails
> with -517 (-EPROBE_DEFER) in bcm2835aux_serial_driver:
> https://elixir.bootlin.com/linux/v5.6/source/drivers/tty/serial/8250/8250_bcm2835aux.c#L52
>
> Without this patch, the lookup works fine.
>
> Please let me know if you need more information. The kernel cmdline I've
> use is: "8250.nr_uarts=1 console=ttyS0,115200n8
> earlycon=uart8250,mmio32,0x3f215040 root=/dev/mmcblk0p2 rootwait rw",
> kernel is compiled with bcm2835_defconfig, booted on Raspberry Pi3b+
> with arch/arm/boot/dts/bcm2837-rpi-3-b.dtb

Thanks for the details! I think it gave me an idea of what might be
going wrong here.

-Saravana