linux-kernel - Re: [PATCH v7 05/24] clocksource: Add a new timer-ingenic driver

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Date:   Wed, 26 Sep 2018 10:05:13 +0200
From:   Daniel Lezcano <daniel.lezcano@...aro.org>
To:     Paul Cercueil <paul@...pouillou.net>
Cc:     Mathieu Malaterre <malat@...ian.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Rob Herring <robh+dt@...nel.org>, linux-doc@...r.kernel.org,
        linux-watchdog@...r.kernel.org, Jonathan Corbet <corbet@....net>,
        od@...c.me, linux-mips@...ux-mips.org,
        Paul Burton <paul.burton@...s.com>,
        Mark Rutland <mark.rutland@....com>, linux-clk@...r.kernel.org,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
        Ralf Baechle <ralf@...ux-mips.org>,
        Thierry Reding <thierry.reding@...il.com>,
        linux-pwm@...r.kernel.org
Subject: Re: [PATCH v7 05/24] clocksource: Add a new timer-ingenic driver

On 26/09/2018 08:01, Paul Cercueil wrote:
> 
> Le 25 sept. 2018 10:12 PM, Daniel Lezcano <daniel.lezcano@...aro.org> a écrit :
>>
>> On 25/09/2018 15:38, Paul Cercueil wrote: 
>>>
>>> Le 24 sept. 2018 9:14 AM, Daniel Lezcano <daniel.lezcano@...aro.org> a écrit : 
>>>>
>>>> On 24/09/2018 08:53, Paul Cercueil wrote: 
>>>>>
>>>>> Le 24 sept. 2018 07:58, Daniel Lezcano <daniel.lezcano@...aro.org> a écrit : 
>>>>>>
>>>>>> On 24/09/2018 07:49, Paul Cercueil wrote: 
>>>>>>>
>>>>>>> Le 24 sept. 2018 07:35, Daniel Lezcano <daniel.lezcano@...aro.org> a 
>>>>>>> écrit : 
>>>>>>>>
>>>>>>>> On 24/09/2018 07:24, Paul Cercueil wrote: 
>>>>>>>>> Hi Daniel, 
>>>>>>>>>
>>>>>>>>> Le 24 sept. 2018 05:12, Daniel Lezcano 
>>>>>>>>> <daniel.lezcano@...aro.org> a écrit : 
>>>>>>>>>>
>>>>>>>>>> On 21/08/2018 19:16, Paul Cercueil wrote: 
>>>>>>>>>>> This driver handles the TCU (Timer Counter Unit) present on 
>>>>>>>>>>> the Ingenic JZ47xx SoCs, and provides the kernel with a 
>>>>>>>>>>> system timer, and optionally with a clocksource and a 
>>>>>>>>>>> sched_clock. 
>>>>>>>>>>>
>>>>>>>>>>> It also provides clocks and interrupt handling to client 
>>>>>>>>>>> drivers. 
>>>>>>>>>>
>>>>>>>>>> Can you provide a much more complete description of the timer 
>>>>>>>>>> in order to make my life easier for the review of this patch? 
>>>>>>>>>
>>>>>>>>> See patch [03/24], it adds a doc file that describes the 
>>>>>>>>> hardware. 
>>>>>>>>
>>>>>>>> Thanks, I went through but it is incomplete to understand what the 
>>>>>>>> timer do. I will reverse-engineer the code but it would help if you 
>>>>>>>> can give the gross approach. Why multiple channels ? mutexes and 
>>>>>>>> completion ? 
>>>>>>>
>>>>>>> Much of the complexity is because of the multi-purpose nature of the 
>>>>>>> TCU channels. Each one can be used as timer/clocksource, or PWM. 
>>>>>>>
>>>>>>> The driver starts by using channels 0 and 1 as system timer and 
>>>>>>> clocksource, respectively, the other ones being unused for now. Then, 
>>>>>>> *if* the PWM driver requests one of the channels in use by the 
>>>>>>> timer/clocksource driver, say channel 0, the timer/clocksource driver 
>>>>>>> will dynamically reassign the system timer to a free channel, from 
>>>>>>> channel 0 to e.g. channel 2. Only in that case the completion/mutex 
>>>>>>> are actually used. 
>>>>>>
>>>>>> Why do you need to do this? Can't be the channels dedicated and reserved 
>>>>>> for clocksource and clockevent? 
>>>>>
>>>>> That's what I had in place (ingenic,timer-channel and ingenic,clocksource-channel DT properties), but Rob didn't want any linux-specific properties in the devicetree binding :( 
>>>>
>>>> Isn't possible to specify the channel to use in the DT? like renesas16 ? 
>>>
>>> That's what I did in V6 (and before), but Rob did not want me to add properties for Linux-specific concepts such as clocksource. 
>>
>> Hmm, I remember something like that, yes but I did a delete of the 
>> previous version when you posted the v7. Can you give a pointer to its 
>> answer ? 
> 
> Yes, this was his answer:
> https://lkml.org/lkml/2018/7/25/508
> 
> Then mine:
> https://lkml.org/lkml/2018/7/30/883

Thanks !


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