linux-kernel - Re: [PATCH] clk: Don't try to enable critical clocks if prepare failed

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Date:   Thu, 26 Dec 2019 20:05:58 -0800
From:   Guenter Roeck <linux@...ck-us.net>
To:     Stephen Boyd <sboyd@...nel.org>
Cc:     Jerome Brunet <jbrunet@...libre.com>,
        Michael Turquette <mturquette@...libre.com>,
        linux-clk@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] clk: Don't try to enable critical clocks if prepare
 failed

On Thu, Dec 26, 2019 at 01:59:19PM -0800, Stephen Boyd wrote:
> Quoting Guenter Roeck (2019-12-26 09:22:10)
> > On 12/26/19 1:51 AM, Jerome Brunet wrote:
> > > 
> > > However, we would not want a critical clock to silently fail to
> > > enable. This might lead to unexpected behavior which are generally hard
> > > (and annoying) to debug.
> > > 
> > > Would you mind adding some kind of warning trace in case this fails ?
> > > 
> > 
> > The really relevant information is:
> > 
> > bcm2835-clk 3f101000.cprman: plld: couldn't lock PLL
> > 
> > which is already displayed (and not surprising since cprman isn't implemented
> > in qemu). While I agree that an error message might be useful, replacing
> > one traceback with another doesn't really make sense to me, and I am not
> > really a friend of spreading tracebacks throughout the kernel. Please feel
> > free to consider this patch to be a bug report, and feel free to ignore it
> > and suggest something else.
> 
> Can the cprman device node be disabled or removed in the DT that qemu
> uses? If it isn't actually implemented then it shouldn't be in the DT.
> Presumably that will make this traceback go away.
> 
cprman feeds all clocks. If the node isn't there, the system doesn't boot.
Also, I don't modify devicetree files in my boot tests; that would defeat
the purpose - like, in this case, to find missing error handling.

Again, please feel free to ignore this patch.

Guenter