Re: [PATCH 2/5] clocksource/drivers/timer-microchip-pit64b: add Microchip PIT64B support

From: Daniel Lezcano <daniel.lezcano@linaro.org>
To: Claudiu.Beznea@microchip.com, alexandre.belloni@bootlin.com
Cc: mark.rutland@arm.com, devicetree@vger.kernel.org,
	linux-kernel@vger.kernel.org, Ludovic.Desroches@microchip.com,
	robh+dt@kernel.org, tglx@linutronix.de,
	linux-arm-kernel@lists.infradead.org, arnd.bergmann@linaro.org
Subject: Re: [PATCH 2/5] clocksource/drivers/timer-microchip-pit64b: add Microchip PIT64B support
Date: Thu, 20 Jun 2019 10:53:35 +0200	[thread overview]
Message-ID: <845acd59-665a-4d0a-3da8-2ba605600928@linaro.org> (raw)
In-Reply-To: <5e3d783e-7bcc-64c1-c814-eaf99a6aa205@microchip.com>

Hi Claudiu,

sorry for the late reply.

On 13/06/2019 16:12, Claudiu.Beznea@microchip.com wrote:
> Hi Daniel,
> 
> On 31.05.2019 13:41, Daniel Lezcano wrote:
>>
>> Hi Claudiu,
>>
>>
>> On 30/05/2019 09:46, Claudiu.Beznea@microchip.com wrote:
>>> Hi Daniel,
>>>
>>> Taking into account the discussion on this tread and the fact that we have
>>> no answer from Rob on this topic (I'm talking about [1]), what do you think
>>> it would be best for this driver to be accepted the soonest? Would it be OK
>>> for you to mimic the approach done by:
>>>
>>> drivers/clocksource/timer-integrator-ap.c
>>>
>>> with the following bindings in DT:
>>>
>>> aliases {
>>> 	arm,timer-primary = &timer2;
>>> 	arm,timer-secondary = &timer1;
>>> };
>>>
>>> also in PIT64B driver?
>>>
>>> Or do you think re-spinning the Alexandre's patches at [2] (which seems to
>>> me like the generic way to do it) would be better?
>>
>> This hardware / OS connection problem is getting really annoying for
>> everyone and this pattern is repeating itself since several years. It is
>> time we fix it properly.
>>
>> The first solution looks hackish from my POV. The second approach looks
>> nicer and generic as you say. So I would vote for [2]
>> flagging approach proposed by Mark [3].
> 
> With this flagging approach this would mean a kind unification of
> clocksource and clockevent functionalities under a single one, right? So
> that the driver would register to the above layers only one device w/ 2
> functionalities (clocksource and clockevent)? Please correct me if I'm
> wrong? If so, from my point of view this would require major re-working of
> clocksource and clockevent subsystems. Correctly if I wrongly understood,
> please.

Well, actually I was not expecting to change all the framework but just
pass a flag to the probe function telling if the node is for a
clocksource, a clockevent or both.

> At the moment we register different functionalities (clocksource and
> clockevent) to the above layers for hardware blocks (e.g. with
> clocksource_register_hz() or clockevents_config_and_register()). If
> hardware can support clocksource and clockevent we register both these
> functionalities, if only one is supported we register only one of these.
> The above layers would choose the best clocksource/clockevent device from
> the available ones based on rating field for each clocksource/clockevent we
> register. In all this current behavior I don't see how these flags would
> interact with clocksource/clockevent subsystem. Could you please let me
> know how do you see these and the way these new flags would interact with
> the layers above the drivers?
>>
>> I added Arnd in Cc in order to have its opinion.
>>
>> [3]
>> https://lore.kernel.org/lkml/20171215113242.skmh5nzr7wqdmvnw@lakrids.cambridge.arm.com/
>>
>>> [1]
>>> https://lore.kernel.org/lkml/20190408151155.20279-1-alexandre.belloni@bootlin.com/#t
>>> [2]
>>> https://lore.kernel.org/lkml/20171213185313.20017-1-alexandre.belloni@free-electrons.com/
>>>
>>
>>
>>
>>
>>
>>

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