linux-kernel - Re: [PATCH v1] serdev: Set fwnode for serdev devices

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Date:   Fri, 3 Mar 2023 09:22:43 -0800
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Stefan Wahren <stefan.wahren@...e.com>,
        Saravana Kannan <saravanak@...gle.com>
Cc:     Rob Herring <robh@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jirislaby@...nel.org>, kernel-team@...roid.com,
        linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1] serdev: Set fwnode for serdev devices

On 3/3/23 03:57, Stefan Wahren wrote:
> Hi,
> 
> Am 02.03.23 um 18:51 schrieb Florian Fainelli:
>>
>>
>> On 3/2/2023 9:20 AM, Saravana Kannan wrote:
>>> On Thu, Mar 2, 2023 at 9:01 AM Stefan Wahren <stefan.wahren@...e.com> 
>>> wrote:
>>>>
>>>> Hi Saravana,
>>>>
>>>> Am 02.03.23 um 03:35 schrieb Saravana Kannan:
>>>>> This allow fw_devlink to do dependency tracking for serdev devices.
>>>>>
>>>>> Reported-by: Florian Fainelli <f.fainelli@...il.com>
>>>>> Link: 
>>>>> https://lore.kernel.org/lkml/03b70a8a-0591-f28b-a567-9d2f736f17e5@gmail.com/
>>>>> Cc: Stefan Wahren <stefan.wahren@...e.com>
>>>>> Signed-off-by: Saravana Kannan <saravanak@...gle.com>
>>>>
>>>> since this fixes an issue on Raspberry Pi 4, shouldn't this be 
>>>> mentioned
>>>> in the commit message and providing a Fixes tag?
>>>
>>> So RPi 4 was never creating a device links between serdev devices and
>>> their consumers. The error message was just a new one I added and we
>>> are noticing and catching the fact that serdev wasn't setting fwnode
>>> for a device.
>>>
>>> I'm also not sure if I can say this commit "Fixes" an issue in serdev
>>> core because when serdev core was written, fw_devlink wasn't a thing.
>>> Once I add Fixes, people will start pulling this into stable
>>> branches/other trees where I don't think this should be pulled into
>>> older stable branches.
>>
>> That is kind of the point of Fixes: tag, is not it? It is appropriate 
>> to list a commit that is not specific to serdev, but maybe a 
>> particular point into the fw_devlink history. Given this did not 
>> appear to have a functional impact, we could go without one.
> 
> i was under the impression that this issue breaks at least Bluetooth on 
> Raspberry Pi 4 because the driver is never probed. I cannot see the 
> success output in Florian's trace. Something like this:
> 
> [    7.124879] hci_uart_bcm serial0-0: supply vbat not found, using 
> dummy regulator
> [    7.131743] hci_uart_bcm serial0-0: supply vddio not found, using 
> dummy regulator
> ...
> [    7.517249] Bluetooth: hci0: BCM: chip id 107
> [    7.517499] Bluetooth: hci0: BCM: features 0x2f
> [    7.519757] Bluetooth: hci0: BCM4345C0
> [    7.519768] Bluetooth: hci0: BCM4345C0 (003.001.025) build 0000
> [    7.539495] Bluetooth: hci0: BCM4345C0 'brcm/BCM4345C0.hcd' Patch
> ...
> [    8.348831] Bluetooth: hci0: BCM43455 37.4MHz Raspberry Pi 3+
> [    8.348845] Bluetooth: hci0: BCM4345C0 (003.001.025) build 0342
> 
> I just want to make sure that 6.2 doesn't have a regression.

My configuration uses hci_uart as a module, and it would always load 
fine, but I suppose I can make sure that even built-in this works 
properly. Give me a day or two to test that.
-- 
Florian