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

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Message-ID: <4f3326c2-186d-2853-fcb6-1210d67a836f@samsung.com>
Date:   Mon, 30 Mar 2020 08:20:22 +0200
From:   Marek Szyprowski <m.szyprowski@...sung.com>
To:     Saravana Kannan <saravanak@...gle.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     "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

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

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland