Re: [PATCH v1 5/5] driver core: Set fw_devlink=on by default

[Guenter Roeck]

On 2/10/21 12:52 PM, Saravana Kannan wrote:
> On Wed, Feb 10, 2021 at 7:10 AM Guenter Roeck <linux@xxxxxxxxxxxx> wrote:
>>
>> On 2/10/21 12:20 AM, Saravana Kannan wrote:
>>> On Tue, Feb 9, 2021 at 9:54 PM Guenter Roeck <linux@xxxxxxxxxxxx> wrote:
>>>>
>>>> On Thu, Dec 17, 2020 at 07:17:03PM -0800, Saravana Kannan wrote:
>>>>> Cyclic dependencies in some firmware was one of the last remaining
>>>>> reasons fw_devlink=on couldn't be set by default. Now that cyclic
>>>>> dependencies don't block probing, set fw_devlink=on by default.
>>>>>
>>>>> Setting fw_devlink=on by default brings a bunch of benefits (currently,
>>>>> only for systems with device tree firmware):
>>>>> * Significantly cuts down deferred probes.
>>>>> * Device probe is effectively attempted in graph order.
>>>>> * Makes it much easier to load drivers as modules without having to
>>>>>   worry about functional dependencies between modules (depmod is still
>>>>>   needed for symbol dependencies).
>>>>>
>>>>> If this patch prevents some devices from probing, it's very likely due
>>>>> to the system having one or more device drivers that "probe"/set up a
>>>>> device (DT node with compatible property) without creating a struct
>>>>> device for it.  If we hit such cases, the device drivers need to be
>>>>> fixed so that they populate struct devices and probe them like normal
>>>>> device drivers so that the driver core is aware of the devices and their
>>>>> status. See [1] for an example of such a case.
>>>>>
>>>>> [1] - https://lore.kernel.org/lkml/CAGETcx9PiX==mLxB9PO8Myyk6u2vhPVwTMsA5NkD-ywH5xhusw@xxxxxxxxxxxxxx/
>>>>> Signed-off-by: Saravana Kannan <saravanak@xxxxxxxxxx>
>>>>
>>>> This patch breaks nios2 boot tests in qemu. The system gets stuck when
>>>> trying to reboot. Reverting this patch fixes the problem. Bisect log
>>>> is attached.
>>>
>>> Thanks for the report Guenter. Can you please try this series?
>>> https://lore.kernel.org/lkml/20210205222644.2357303-1-saravanak@xxxxxxxxxx/
>>>
>>
>> Not this week. I have lots of reviews to complete before the end of the week,
>> with the 5.12 commit window coming up.
> 
> Ok. By next week, all the fixes should be in linux-next too. So it
> should be easier if you choose to test.
> 
>> Given the number of problems observed, I personally think that it is way
>> too early for this patch. We'll have no end of problems if it is applied
>> to the upstream kernel in the next commit window. Of course, that is just
>> my personal opinion.
> 
> You had said "with 115 of 430 boot tests failing in -next" earlier.
> Just to be sure I understand it right, you are not saying this patch
> caused them all right? You are just saying that 115 general boot
> failures that might mask fw_devlink issues in some of them, right?
> 

Correct.

Guenter