From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paul Cercueil Subject: Re: [PATCH v4 7/8] clocksource: Add a new timer-ingenic driver Date: Sat, 31 Mar 2018 19:46:06 +0200 Message-ID: <4532f9e86184afab8c46e8debd8abe61@crapouillou.net> References: <20180110224838.16711-2-paul@crapouillou.net> <20180317232901.14129-1-paul@crapouillou.net> <20180317232901.14129-8-paul@crapouillou.net> <06976e4ae275c4cc0bddacc5e0c0c9a9@crapouillou.net> <1522335149.1792.0@smtp.crapouillou.net> <2234006b-30ff-d5a8-b14a-d6e307c06145@linaro.org> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Return-path: Subject: In-Reply-To: <2234006b-30ff-d5a8-b14a-d6e307c06145@linaro.org> Sender: linux-kernel-owner@vger.kernel.org To: Daniel Lezcano Cc: Thomas Gleixner , Jason Cooper , Marc Zyngier , Lee Jones , Ralf Baechle , Rob Herring , Jonathan Corbet , Mark Rutland , James Hogan , Maarten ter Huurne , linux-clk@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mips@linux-mips.org, linux-doc@vger.kernel.org List-Id: devicetree@vger.kernel.org Le 2018-03-31 10:10, Daniel Lezcano a écrit : > On 29/03/2018 16:52, Paul Cercueil wrote: >> >> >> Le mer. 28 mars 2018 à 18:25, Daniel Lezcano >> >> a écrit : >>> On 28/03/2018 17:15, Paul Cercueil wrote: >>>>  Le 2018-03-24 07:26, Daniel Lezcano a écrit : >>>>>  On 18/03/2018 00:29, 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. >>>>> >>>>>  Please provide a more detailed description about the timer. >>>> >>>>  There's a doc file for that :) >>> >>> Usually, when there is a new driver I ask for a description in the >>> changelog for reference. >>> >>>>>  Where is the clocksource ? >>>> >>>>  Right, there is no clocksource, just timers. >>>> >>>>>  I don't see the point of using channel idx and pwm checking here. >>>>> >>>>>  There is one clockevent, why create multiple channels ? Can't you >>>>> stick >>>>>  to the usual init routine for a timer. >>>> >>>>  So the idea is that we use all the TCU channels that won't be used >>>> for PWM >>>>  as timers. Hence the PWM checking. Why is this bad? >>> >>> It is not bad but arguable. By checking the channels used by the pwm >>> in >>> the code, you introduce an adherence between two subsystems even if >>> it >>> is just related to the DT parsing part. >>> >>> As it is not needed to have more than one timer in the time framework >>> (at least with the same characteristics), the pwm channels check is >>> pointless. We can assume the author of the DT file is smart enough to >>> prevent conflicts and define a pwm and a timer properly instead of >>> adding more code complexity. >>> >>> In addition, simplifying the code will allow you to use the timer-of >>> code and reduce very significantly the init function. >> >> That's what I had in my V1 and V2, my DT node for the timer-ingenic >> driver >> had a "timers" property (e.g. "timers = <4 5>;") to select the >> channels >> that >> should be used as timers. Then Rob told me I shouldn't do that, and >> instead >> detect the channels that will be used for PWM. >> > > [ ... ] > > How do you specify the channels used for PWM ? To detect the channels that will be used as PWM I parse the whole devicetree searching for "pwms" properties; check that the PWM handle is for our TCU PWM driver; then read the PWM number from there. Of course it's hackish, and it only works for devicetree. I preferred the method with the "timers" property. >>>>>> >>>>>>  +config INGENIC_TIMER >>>>>>  +    bool "Clocksource/timer using the TCU in Ingenic JZ SoCs" >>>>>>  +    depends on MACH_INGENIC || COMPILE_TEST >>>>> >>>>>  bool "Clocksource/timer using the TCU in Ingenic JZ SoCs" if >>>>> COMPILE_TEST >>>>> >>>>>  Remove the depends MACH_INGENIC. >>>> >>>>  This driver is not useful on anything else than Ingenic SoCs, why >>>> should I >>>>  remove MACH_INGENIC then? >>> >>> For COMPILE_TEST on x86. >> >> Well that's a logical OR right here, so it will work... > > Right, I missed the second part of the condition. For consistency > reason, we don't add a dependency on the platform. The platform will > select it. Look the other timer options and you will see there is no > MACH deps. I'm trying consolidating all these options to have same > format and hopefully factor them out. I'm all for factorisation, but what I dislike with not depending on MACH_INGENIC, is that the driver now appears in the menuconfig for every arch, even if it only applies to one MIPS SoC. Regards, -Paul