linux-kernel - Re: [PATCH v1] clocksource: Avoid creating dead devices

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Message-ID: <814e5b06-dde9-f59a-735a-39d7e41efc67@linaro.org>
Date:   Wed, 4 Mar 2020 20:56:49 +0100
From:   Daniel Lezcano <daniel.lezcano@...aro.org>
To:     Saravana Kannan <saravanak@...gle.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Android Kernel Team <kernel-team@...roid.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v1] clocksource: Avoid creating dead devices

On 04/03/2020 20:30, Saravana Kannan wrote:
> On Thu, Feb 27, 2020 at 1:22 PM Saravana Kannan <saravanak@...gle.com> wrote:
>>
>> On Thu, Feb 27, 2020 at 1:06 AM Daniel Lezcano
>> <daniel.lezcano@...aro.org> wrote:
>>>
>>> On 11/01/2020 06:21, Saravana Kannan wrote:
>>>> 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.

TBH, I'm missing the rational with the explanation and the code. Can you
elaborate or rephrase it?


>>>> Signed-off-by: Saravana Kannan <saravanak@...gle.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 ee9574da53c0..a10f28d750a9 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);
>>>
>>> Isn't it in conflict with:
>>>
>>> drivers/clocksource/ingenic-timer.c
>>>
>>> ?
>>
>> No, it won't interfere with that driver because:
>> 1. This flag is getting set only if the driver already registered a
>> timer init function using TIMER_OF_DECLARE.
>> 2. And if the function fails, we clear the flag.
>>
>> So in the case of ingenic-timer, the device will still be there and be
>> probed by the driver.
> 
> Daniel, friendly reminder. Or do you have a patchworks link too that I
> can keep an eye on?



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