Re: [PATCH] mailbox: mtk-cmdq: Add unregister mailbox controller in cmdq_remove()

[AngeloGioacchino Del Regno]

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@xxxxxxxxxxxx>
> > > > >
> > > > > Hello,
> > > > >
> > > > > I think you forgot about...
> https://lore.kernel.org/all/6fcd48b14e865c25e6db7559fe6b946537bfa0ce.camel@xxxxxxxxxxxx/
> > > > >
> > > >
> > > > 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);
> > > > > >