Re: [PATCH v4 3/8] doc: Add doc for the Ingenic TCU hardware

[Paul Cercueil <paul@crapouillou.net>]

Le 2018-03-18 00:52, Randy Dunlap a écrit :
> On 03/17/2018 04:28 PM, Paul Cercueil wrote:
>> Add a documentation file about the Timer/Counter Unit (TCU)
>> present in the Ingenic JZ47xx SoCs.
>> 
>> Signed-off-by: Paul Cercueil <paul@crapouillou.net>
>> ---
>>  Documentation/mips/00-INDEX        |  3 +++
>>  Documentation/mips/ingenic-tcu.txt | 50 
>> ++++++++++++++++++++++++++++++++++++++
>>  2 files changed, 53 insertions(+)
>>  create mode 100644 Documentation/mips/ingenic-tcu.txt
>> 
>>  v4: New patch in this series
> 
>> diff --git a/Documentation/mips/ingenic-tcu.txt 
>> b/Documentation/mips/ingenic-tcu.txt
>> new file mode 100644
>> index 000000000000..2508e5793da8
>> --- /dev/null
>> +++ b/Documentation/mips/ingenic-tcu.txt
>> @@ -0,0 +1,50 @@
>> +Ingenic JZ47xx SoCs Timer/Counter Unit hardware
>> +-----------------------------------------------
>> +
>> +The Timer/Counter Unit (TCU) in Ingenic JZ47xx SoCs is a 
>> multi-function
>> +hardware block. It features eight channels, that can be used as 
>> counters,
> 
>                     drop comma ............. ^

Ok.

>> +timers, or PWM.
>> +
>> +- JZ4770 introduced a separate channel, called Operating System Timer 
>> (OST).
>> +  It is a 64-bit programmable timer.
>> +
>> +- Each one of the eight channels has its own clock, which can be 
>> reparented
>> +  to three different clocks (pclk, ext, rtc), gated, and reclocked, 
>> through
>> +  their TCSR register.
>> +  * The watchdog and OST hardware blocks also feature a TCSR register 
>> with
>> +	the same format in their register space.
>> +  * The TCU registers used to gate/ungate can also gate/ungate the 
>> watchdog
>> +	and OST clocks.
>> +
>> +- On SoCs >= JZ4770, there are two different modes:
>> +  * Channels 0, 3-7 operate in TCU1 mode: they cannot work in sleep 
>> mode,
>> +	but are easier to operate.
>> +  * Channels 1-2 operate in TCU2 mode: they can work in sleep mode, 
>> but
>> +	the operation is a bit more complicated than with TCU1 channels.
>> +
>> +- Each channel can generate an interrupt. Some channels share an 
>> interrupt
>> +  line, some don't, and this changes between SoC versions:
>> +  * on JZ4740, timer 0 and timer 1 have their own interrupt line; 
>> others share
>> +	one interrupt line.
>> +  * on JZ4770 and JZ4780, timer 5 has its own interrupt; timers 0-4 
>> and 6-7 all
>> +	use one interrupt line; the OST uses the last interrupt.
> 
> "The OST uses the last interrupt." is not clear to someone who doesn't 
> know
> about this hardware. (I can read it several ways.)
> 
> Does it mean that the 4770 and 4780 have 3 interrupt lines used like 
> so?
> 
> - timer 5 uses one interrupt line
> - timers 0-4 and 6-7 use a second interrupt line
> - the OST uses a third interrupt line

Correct. I'll make it more obvious.

Thanks,
-Paul

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