linux-kernel - Re: [PATCH] clk: tegra: probe deferral error reporting

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Date:   Thu, 26 Jul 2018 09:55:16 +0200
From:   Stefan Agner <stefan@...er.ch>
To:     Stephen Boyd <sboyd@...nel.org>
Cc:     Marcel Ziswiler <marcel@...wiler.com>,
        Peter Geis <pgwipeout@...il.com>, linux-kernel@...r.kernel.org,
        linux-tegra@...r.kernel.org,
        Marcel Ziswiler <marcel.ziswiler@...adex.com>,
        Thierry Reding <thierry.reding@...il.com>,
        Prashant Gaikwad <pgaikwad@...dia.com>,
        Peter De Schrijver <pdeschrijver@...dia.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Michael Turquette <mturquette@...libre.com>,
        linux-clk@...r.kernel.org, linux-tegra-owner@...r.kernel.org
Subject: Re: [PATCH] clk: tegra: probe deferral error reporting

On 26.07.2018 09:31, Stephen Boyd wrote:
> Quoting Peter Geis (2018-07-25 16:42:34)
>> On 7/25/2018 7:24 PM, Stephen Boyd wrote:
>> > Quoting Marcel Ziswiler (2018-07-20 00:54:22)
>> >> From: Marcel Ziswiler <marcel.ziswiler@...adex.com>
>> >>
>> >> Actually report the error code from devm_regulator_get() which may as
>> >> well just be a probe deferral.
>> >>
>> >> Signed-off-by: Marcel Ziswiler <marcel.ziswiler@...adex.com>
>> >>
>> >> ---
>> >>
>> >>   drivers/clk/tegra/clk-dfll.c | 5 +++--
>> >>   1 file changed, 3 insertions(+), 2 deletions(-)
>> >>
>> >> diff --git a/drivers/clk/tegra/clk-dfll.c b/drivers/clk/tegra/clk-dfll.c
>> >> index 48ee43734e05..b2123084e175 100644
>> >> --- a/drivers/clk/tegra/clk-dfll.c
>> >> +++ b/drivers/clk/tegra/clk-dfll.c
>> >> @@ -1609,8 +1609,9 @@ int tegra_dfll_register(struct platform_device *pdev,
>> >>
>> >>          td->vdd_reg = devm_regulator_get(td->dev, "vdd-cpu");
>> >>          if (IS_ERR(td->vdd_reg)) {
>> >> -               dev_err(td->dev, "couldn't get vdd_cpu regulator\n");
>> >> -               return PTR_ERR(td->vdd_reg);
>> >> +               ret = PTR_ERR(td->vdd_reg);
>> >> +               dev_err(td->dev, "couldn't get vdd_cpu regulator: %d\n", ret);
>> >
>> > Do you want to know that a probe defer is happening? Usually patches are
>> > sent to make that error path silent.
>> >
>>
>> Just asking as the newbie here, but shouldn't probe deferral be
>> regulated to dev_debug?
>> Then pass any other error code as dev_err.
> 
> Yes probe defer should be relegated to debug level prints. Or really, we
> should introduce a more complicated system to make debugging probe defer
> errors simpler by informing us which driver is probe defering on what
> resource by putting debug prints in each framework that returns probe
> defer errors instead of updating each driver that uses these frameworks
> and thinks it needs to print errors in these cases. And hide all that
> behind some kernel commandline parameter and/or Kconfig option that lets
> us turn the prints off all the time if we're not developing drivers or
> testing things.

Afaict, that is already there in:
drivers/base/dd.c:really_probe()

So I suggest to just silence the EPROBE_DEFER case, e.g.\


	if (IS_ERR(td->vdd_reg)) {
		ret = PTR_ERR(td->vdd_reg);
		if (ret != -EPROBE_DEFER)
			dev_err(td->dev, "couldn't get vdd_cpu regulator: %d\n", ret);

		return ret;
	}

--
Stefan


> 
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