linux-kernel - Re: [PATCH] mailbox: mtk-cmdq: Add unregister mailbox controller in cmdq

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Message-ID: <aa1cfc45-b271-43fa-85fc-264ea16574d9@collabora.com>
Date: Wed, 17 Jul 2024 15:28:32 +0200
From: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
To: Jason-JH Lin (林睿祥) <Jason-JH.Lin@...iatek.com>,
 "jassisinghbrar@...il.com" <jassisinghbrar@...il.com>,
 "chunkuang.hu@...nel.org" <chunkuang.hu@...nel.org>
Cc: "linux-arm-kernel@...ts.infradead.org"
 <linux-arm-kernel@...ts.infradead.org>,
 "matthias.bgg@...il.com" <matthias.bgg@...il.com>,
 Nancy Lin (林欣螢) <Nancy.Lin@...iatek.com>,
 "linux-mediatek@...ts.infradead.org" <linux-mediatek@...ts.infradead.org>,
 "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
 Singo Chang (張興國) <Singo.Chang@...iatek.com>,
 Project_Global_Chrome_Upstream_Group
 <Project_Global_Chrome_Upstream_Group@...iatek.com>
Subject: Re: [PATCH] mailbox: mtk-cmdq: Add unregister mailbox controller in
 cmdq_remove()

Il 17/07/24 05:44, Jason-JH Lin (林睿祥) ha scritto:
> On Tue, 2024-06-18 at 13:47 +0200, AngeloGioacchino Del Regno wrote:
>> Il 18/06/24 05:28, Jason-JH Lin (林睿祥) ha scritto:
>>> Hi Angelo,
>>>
>>> On Fri, 2024-06-14 at 00:52 +0800, Jason-JH.Lin wrote:
>>>> Hi Angelo,
>>>>
>>>> On Thu, 2024-06-13 at 17:10 +0200, AngeloGioacchino Del Regno
>>>> wrote:
>>>>> Il 13/06/24 17:06, Jason-JH.Lin ha scritto:
>>>>>> Add unregister mailbox controller in cmdq_remove to fix cmdq
>>>>>> unbind
>>>>>> WARN_ON message from pm_runtime_get_sync() in
>>>>>> cmdq_mbox_shutdown().
>>>>>>
>>>>>> Fixes: 623a6143a845 ("mailbox: mediatek: Add Mediatek CMDQ
>>>>>> driver")
>>>>>> Signed-off-by: Jason-JH.Lin <jason-jh.lin@...iatek.com>
>>>>>
>>>>> Hello,
>>>>>
>>>>> I think you forgot about...
>>>>>
>>>>>
>>>>
>>>>
>>>
>>>
> https://lore.kernel.org/all/6fcd48b14e865c25e6db7559fe6b946537bfa0ce.camel@mediatek.com/
>>>>>
>>>>
>>>> I'll send this series next week after testing it.
>>>>
>>>>
>>>>> ...as that would also resolve this one without any hacks.
>>>>
>>>> I thought it was another problem, so I sent this patch.
>>>>
>>>> After looking to the kerneldoc of
>>>> devm_mbox_controller_unregister(),
>>>> I
>>>> found that it's not necessary to call this anywhere.
>>>>
>>>> I'll drop this patch. Thanks for the review.
>>>
>>> I found that the series of "Move pm_runimte_get and put to
>>> mbox_chan_ops API" can not fix this unbind crash issue.
>>>
>>> It seems they are 2 different issues.
>>>
>>> So I think calling devm_mbox_controller_unregister() in
>>> cmdq_remove()
>>> can ensure the CMDQ device is not removed and be paired to
>>> cmdq_probe().
>>>
>>
>> Can you please paste the stack trace of that warning that you're
>> seeing when
>> calling cmdq_remove()?
>>
>> I'm not convinced that this is the best solution - it might be, but I
>> have
>> a hunch that there might be a better way to address this issue.
>>
> 
> After tracing the stack trace again, I found this call trace warning is
> caused in WARN_ON(pm_runtime_get_sync(cmdq->mbox.dev) < 0). The return
> value of pm_runtime_get_sync() is -13(-EACCESS) that's caused by
> calling pm_runtime_disable() before calling pm_runtime_get_sync().
> 
> CMDQ driver uses devm_mbox_controller_register() in cmdq_probe() to
> bind the cmdq device to the mbox_controller, so
> devm_mbox_controller_unregister() will automatically unregister the
> device bound to the mailbox controller when the device-managed resource
> is removed. That means devm_mbox_controller_unregister() and
> cmdq_mbox_shoutdown() will be called after cmdq_remove().
> 
> CMDQ driver also uses devm_pm_runtime_enable() in cmdq_probe() after
> devm_mbox_controller_register(), so that devm_pm_runtime_disable() will
> be called after cmdq_remove(), but before
> devm_mbox_controller_unregister().
> 
> 
> To fix this problem, we need to make devm_pm_runtime_disable() be
> called after devm_mbox_controller_unregister().
> 
> I've tried 2 ways can fix this problem:
> - Swap the sequence of devm_mbox_controller_register() and
> devm_pm_runtime_enable() in cmdq_probe()
> - Change to use mbox_controller_register() in cmdq_probe() and use
> mbox_controller_unregister() in cmdq_probe()
> 

Hey.

That's a nice conclusion here!
If the first one has no issues, go for the first one: that's just about
moving a call upwards, noiseless and pretty.

Cheers!
Angelo

> Which one do you think is better?
> 
> Regards,
> Jason-JH.Lin
> 
>> Thanks!
>> Angelo
>>
>>> Regards,
>>> Jason-JH.Lin
>>>
>>>>
>>>> Regards,
>>>> Jason-JH.Lin
>>>>
>>>>>
>>>>> Cheers,
>>>>> Angelo
>>>>>
>>>>>> ---
>>>>>>     drivers/mailbox/mtk-cmdq-mailbox.c | 2 ++
>>>>>>     1 file changed, 2 insertions(+)
>>>>>>
>>>>>> diff --git a/drivers/mailbox/mtk-cmdq-mailbox.c
>>>>>> b/drivers/mailbox/mtk-cmdq-mailbox.c
>>>>>> index 4aa394e91109..1399e18a39a4 100644
>>>>>> --- a/drivers/mailbox/mtk-cmdq-mailbox.c
>>>>>> +++ b/drivers/mailbox/mtk-cmdq-mailbox.c
>>>>>> @@ -371,6 +371,8 @@ static void cmdq_remove(struct
>>>>>> platform_device
>>>>>> *pdev)
>>>>>>     {
>>>>>>     	struct cmdq *cmdq = platform_get_drvdata(pdev);
>>>>>>     
>>>>>> +	devm_mbox_controller_unregister(&pdev->dev, &cmdq-
>>>>>>> mbox);
>>>>>> +
>>>>>>     	if (cmdq->pdata->sw_ddr_en)
>>>>>>     		cmdq_sw_ddr_enable(cmdq, false);
>>>>>>     
>>>>>
>>>>>
>>
>>