linux-kernel - Re: [tip: timers/core] clocksource/drivers/timer-probe: Avoid creating dead devices

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Date:   Wed, 25 Mar 2020 21:29:57 +0000
From:   Jon Hunter <jonathanh@...dia.com>
To:     Ionela Voinescu <ionela.voinescu@....com>,
        <linux-kernel@...r.kernel.org>,
        Saravana Kannan <saravanak@...gle.com>,
        Daniel Lezcano <daniel.lezcano@...aro.org>
CC:     <linux-tip-commits@...r.kernel.org>, x86 <x86@...nel.org>,
        <liviu.dudau@....com>, <sudeep.holla@....com>,
        <lorenzo.pieralisi@....com>,
        linux-tegra <linux-tegra@...r.kernel.org>
Subject: Re: [tip: timers/core] clocksource/drivers/timer-probe: Avoid
 creating dead devices


On 24/03/2020 17:59, Ionela Voinescu wrote:
> Hi guys,
> 
> On Thursday 19 Mar 2020 at 08:47:46 (-0000), tip-bot2 for Saravana Kannan wrote:
>> The following commit has been merged into the timers/core branch of tip:
>>
>> Conommit-ID:     4f41fe386a94639cd9a1831298d4f85db5662f1e
>> Gitweb:        https://git.kernel.org/tip/4f41fe386a94639cd9a1831298d4f85db5662f1e
>> Author:        Saravana Kannan <saravanak@...gle.com>
>> AuthorDate:    Fri, 10 Jan 2020 21:21:25 -08:00
>> Committer:     Daniel Lezcano <daniel.lezcano@...aro.org>
>> CommitterDate: Tue, 17 Mar 2020 13:10:07 +01:00
>>
>> clocksource/drivers/timer-probe: Avoid creating dead devices
>>
>> Timer initialization is done during early boot way before the driver
>> core starts processing devices and drivers. Timers initialized during
>> this early boot period don't really need or use a struct device.
>>
>> However, for timers represented as device tree nodes, the struct devices
>> are still created and sit around unused and wasting memory. This change
>> avoid this by marking the device tree nodes as "populated" if the
>> corresponding timer is successfully initialized.
>>
>> Signed-off-by: Saravana Kannan <saravanak@...gle.com>
>> Signed-off-by: Daniel Lezcano <daniel.lezcano@...aro.org>
>> Link: https://lore.kernel.org/r/20200111052125.238212-1-saravanak@google.com
>> ---
>>  drivers/clocksource/timer-probe.c | 2 ++
>>  1 file changed, 2 insertions(+)
>>
>> diff --git a/drivers/clocksource/timer-probe.c b/drivers/clocksource/timer-probe.c
>> index ee9574d..a10f28d 100644
>> --- a/drivers/clocksource/timer-probe.c
>> +++ b/drivers/clocksource/timer-probe.c
>> @@ -27,8 +27,10 @@ void __init timer_probe(void)
>>  
>>  		init_func_ret = match->data;
>>  
>> +		of_node_set_flag(np, OF_POPULATED);
>>  		ret = init_func_ret(np);
>>  		if (ret) {
>> +			of_node_clear_flag(np, OF_POPULATED);
>>  			if (ret != -EPROBE_DEFER)
>>  				pr_err("Failed to initialize '%pOF': %d\n", np,
>>  				       ret);
>>
> 
> This patch is creating problems on some vexpress platforms - ones that
> are using CLKSRC_VERSATILE (drivers/clocksource/timer-versatile.c).
> I noticed issues on TC2 and FVPs (fixed virtual platforms) starting with
> next-20200318 and still reproducible with next-20200323.

I am also seeing a regression on tegra30-cardhu-a04 when testing system
suspend on -next. Bisect is pointing to this commit and reverting on top
of -next fixes the problem. Unfortunately, there is no crash dump
observed, but the device hangs somewhere when testing suspend.

I have not looked into this any further but wanted to report the problem.

Cheers
Jon

-- 
nvpublic