linux-kernel - Re: [PATCH v2 5/6] clocksource: Add a new timer-ingenic driver

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Date:   Wed, 03 Jan 2018 22:56:16 +0100
From:   Paul Cercueil <paul@...pouillou.net>
To:     Rob Herring <robh@...nel.org>
Cc:     Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...eaurora.org>,
        Mark Rutland <mark.rutland@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Jason Cooper <jason@...edaemon.net>,
        Marc Zyngier <marc.zyngier@....com>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Lee Jones <lee.jones@...aro.org>, linux-clk@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 5/6] clocksource: Add a new timer-ingenic driver

Hi,

Le mer. 3 janv. 2018 à 22:08, Rob Herring <robh@...nel.org> a écrit :
> On Mon, Jan 01, 2018 at 03:33:43PM +0100, Paul Cercueil wrote:
>>  This driver will use the TCU (Timer Counter Unit) present on the 
>> Ingenic
>>  JZ47xx SoCs to provide the kernel with a clocksource and timers.
>> 
>>  Signed-off-by: Paul Cercueil <paul@...pouillou.net>
>>  ---
>>   .../devicetree/bindings/timer/ingenic,tcu.txt      |  35 +++
> 
> Separate patch please.

OK.

>>   drivers/clocksource/Kconfig                        |   8 +
>>   drivers/clocksource/Makefile                       |   1 +
>>   drivers/clocksource/timer-ingenic.c                | 256 
>> +++++++++++++++++++++
>>   4 files changed, 300 insertions(+)
>>   create mode 100644 
>> Documentation/devicetree/bindings/timer/ingenic,tcu.txt
>>   create mode 100644 drivers/clocksource/timer-ingenic.c
>> 
>>   v2: Use SPDX identifier for the license
>> 
>>  diff --git 
>> a/Documentation/devicetree/bindings/timer/ingenic,tcu.txt 
>> b/Documentation/devicetree/bindings/timer/ingenic,tcu.txt
>>  new file mode 100644
>>  index 000000000000..e4944972ea53
>>  --- /dev/null
>>  +++ b/Documentation/devicetree/bindings/timer/ingenic,tcu.txt
>>  @@ -0,0 +1,35 @@
>>  +Ingenic JZ47xx SoCs Timer/Counter Unit driver
>>  +---------------------------------------------
>>  +
>>  +Required properties:
>>  +
>>  +- compatible : should be "ingenic,<socname>-tcu". Valid strings 
>> are:
>>  +  * ingenic,jz4740-tcu
>>  +  * ingenic,jz4770-tcu
>>  +  * ingenic,jz4780-tcu
>>  +- interrupt-parent : phandle of the TCU interrupt controller.
>>  +- interrupts : Specifies the interrupts the controller is 
>> connected to.
>>  +- clocks : List of phandle & clock specifiers for the TCU clocks.
>>  +- clock-names : List of name strings for the TCU clocks.
>>  +- ingenic,channels: a list of TCU channels to be used as timers.
> 
> Why is this needed? This looks like you are trying to assign certain
> timers to clocksource and clockevent. A common problem, but one that
> should be decided by describing h/w features. There must be some
> property present or missing to make you decide to use a given channel 
> or
> not.

Well, it's not easy; some TCU channels will be used as PWM, and there's 
no way
to know that when the clocksource driver probes. And which ones are PWM 
/ which
ones are not, is board-specific. If you have a better solution though, 
I take it.

>>  +
>>  +Example:
>>  +
>>  +/ {
>>  +	regmap {
>>  +		compatible = "simple-mfd", "syscon";
>>  +		reg = <0x10002000 0x1000>;
>>  +
>>  +		tcu: timer {
>>  +			compatible = "ingenic,jz4740-tcu";
>>  +
>>  +			clocks = <&tcu 0>, <&tcu 1>;
>>  +			clock-names = "timer0", "timer1";
> 
> It's curious that you have timer0 and timer1 here and then channels 0
> and 1 below. Would your clocks change if you use channel 2 for 
> example?
> The binding should be a list of clock connections in the h/w, not
> just what the driver needs or what the used h/w configuration is.
> 
> Rob

I only put these to simplify the example, but you're right, I should 
have
all the timer clocks supplied there.

Thanks,
-Paul