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

From: Daniel Lezcano
Date: Mon Sep 24 2018 - 03:14:33 EST


On 24/09/2018 08:53, Paul Cercueil wrote:
>
> Le 24 sept. 2018 07:58, Daniel Lezcano <daniel.lezcano@xxxxxxxxxx> a Ãcrit :
>>
>> On 24/09/2018 07:49, Paul Cercueil wrote:
>>>
>>> Le 24 sept. 2018 07:35, Daniel Lezcano <daniel.lezcano@xxxxxxxxxx> a
>>> Ãcrit :
>>>>
>>>> On 24/09/2018 07:24, Paul Cercueil wrote:
>>>>> Hi Daniel,
>>>>>
>>>>> Le 24 sept. 2018 05:12, Daniel Lezcano
>>>>> <daniel.lezcano@xxxxxxxxxx> a Ãcrit :
>>>>>>
>>>>>> 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 ?

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