linux-kernel - Re: [PATCH v2] driver core: Make cycle dev_info() message dev

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Date:   Fri, 4 Jun 2021 20:18:52 +0000
From:   Stephen Boyd <swboyd@...omium.org>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-kernel@...r.kernel.org,
        Saravana Kannan <saravanak@...gle.com>
Subject: Re: [PATCH v2] driver core: Make cycle dev_info() message dev_dbg()

Quoting Greg Kroah-Hartman (2021-06-04 06:00:47)
> On Thu, Jun 03, 2021 at 01:21:16PM -0700, Stephen Boyd wrote:
> > This seems to mostly print debug information about device link stuff at
> > boot. It doesn't seem very useful outside of debugging so move it to
> > dev_dbg().
>
> What messages at boot time are you seeing with this that should not be
> there?  Shouldn't we fix the root cause here and not paper over it by
> just lowering the logging level?

Is there any problem? If they're a problem then shouldn't the printk be
at least warning level, pr_warn() if not pr_err()? I thought that
sometimes devices have cyclic links so we want to back off at that time
and stop trying.

>
> What drivers are having problems to trigger this?
>

It looks to be mostly the coresight devices that print this info message
for me. The other one is the display panel. The coresight devices are in
arch/arm64/boot/dts/qcom/sc7180.dtsi

[    0.545197] amba 6041000.funnel: Fixing up cyclic dependency with 6002000.stm
[    0.547173] amba 6045000.funnel: Fixing up cyclic dependency with
6042000.funnel
[    0.548032] amba 6045000.funnel: Fixing up cyclic dependency with
6041000.funnel
[    0.549899] amba 6048000.etr: Fixing up cyclic dependency with
6046000.replicator
[    0.551371] amba 6b04000.funnel: Fixing up cyclic dependency with
6045000.funnel
[    0.552781] amba 6b05000.etf: Fixing up cyclic dependency with 6b04000.funnel
[    0.554258] amba 6b06000.replicator: Fixing up cyclic dependency
with 6b05000.etf
[    0.555136] amba 6b06000.replicator: Fixing up cyclic dependency
with 6046000.replicator
[    0.560889] amba 7800000.funnel: Fixing up cyclic dependency with 7740000.etm
[    0.561726] amba 7800000.funnel: Fixing up cyclic dependency with 7640000.etm
[    0.562553] amba 7800000.funnel: Fixing up cyclic dependency with 7540000.etm
[    0.563388] amba 7800000.funnel: Fixing up cyclic dependency with 7440000.etm
[    0.564205] amba 7800000.funnel: Fixing up cyclic dependency with 7340000.etm
[    0.565034] amba 7800000.funnel: Fixing up cyclic dependency with 7240000.etm
[    0.565867] amba 7800000.funnel: Fixing up cyclic dependency with 7140000.etm
[    0.566693] amba 7800000.funnel: Fixing up cyclic dependency with 7040000.etm
[    0.568196] amba 7810000.funnel: Fixing up cyclic dependency with
7800000.funnel
[    0.569047] amba 7810000.funnel: Fixing up cyclic dependency with
6042000.funnel
[    0.623637] i2c 2-002d: Fixing up cyclic dependency with panel
[    1.108625] platform ae94000.dsi: Fixing up cyclic dependency with 2-002d
[    1.115646] platform ae94000.dsi: Fixing up cyclic dependency with
ae01000.mdp

I suppose with the graph binding making links we get these cyclic
dependency messages now.