Le 3 oct. 2018 3:02 PM, Daniel Lezcano <daniel.lezcano@xxxxxxxxxx> a écrit : > > On 03/10/2018 14:51, Paul Cercueil wrote: > > > > Le 3 oct. 2018 2:47 PM, Daniel Lezcano <daniel.lezcano@xxxxxxxxxx> a > > écrit : > >> > >> On 03/10/2018 12:32, Paul Cercueil wrote: > >>> > >>> Le 1 oct. 2018 10:48, Daniel Lezcano <daniel.lezcano@xxxxxxxxxx> > >>> a écrit : > >>>> > >>>> On 31/07/2018 00:01, Paul Cercueil wrote: > >>>> > >>>> [ ... ] > >>>> > >>>>>>> +- ingenic,timer-channel: Specifies the TCU channel that > >>>>>>> should be used as + system timer. If not provided, the > >>>>>>> TCU channel 0 is used for the system timer. + +- > >>>>>>> ingenic,clocksource-channel: Specifies the TCU channel > >>>>>>> that should be used + as clocksource and sched_clock. It > >>>>>>> must be a different channel than the one + used as > >>>>>>> system timer. If not provided, neither a clocksource nor > >>>>>>> a + sched_clock is instantiated. > >>>>>> > >>>>>> clocksource and sched_clock are Linux specific and don't > >>>>>> belong in DT. You should define properties of the hardware > >>>>>> or use existing properties like interrupts or clocks to > >>>>>> figure out which channel to use. For example, if some > >>>>>> channels don't have an interrupt, then use them for > >>>>>> clocksource and not a clockevent. Or you could have timers > >>>>>> that run in low-power modes or not. If all the channels are > >>>>>> identical, then it shouldn't matter which ones the OS > >>>>>> picks. > >>>> > >>>> It can't work in this case because the pmw and the timer driver > >>>> are not communicating and the first one can stole a channel to > >>>> the last one. > >>> > >>> In that particular case the timer driver will always request its > >>> channels first; with no timer set the system hangs before > >>> subsys_initcall, and the PWM driver is a subnode of the timer > >>> node, so is probed only after the timer probed. > >>> > >>>>> We already talked about that. All the TCU channels can be > >>>>> used for PWM. The problem is I cannot know from the driver's > >>>>> scope which channels will be free and which channels will be > >>>>> requested for PWM. You suggested that I parse the devicetree > >>>>> for clients, and I did that in the V3/V4 patchset. But it > >>>>> only works for clients requesting through devicetree, not > >>>>> from platform code or even sysfs. > >>>>> > >>>>> One thing I can try is to dynamically change the channels the > >>>>> system timer and clocksource are using when the current ones > >>>>> are requested for PWM. But that sounds hardcore... > >>>> > >>>> Yes, it is :/ > >>>> > >>>> Sorry for letting you wasting time and effort to write an > >>>> overkill code not suitable for upstream. > >>>> > >>>> A very gross thought, wouldn't be possible to "register" a > >>>> channel from the timer driver code in a shared data area (but > >>>> well self-encapsulated) and the pwm code will check such > >>>> channel isn't in use ? > >>> > >>> Probably, but it's the contrary I need to do. The timer driver > >>> code can use any channel, and probes first. The PWM driver code > >>> must use specific channels, and probes last. So either the timer > >>> driver knows what channels it can't use, thanks to a device > >>> property, or it adapts itself when a channel in use is requested > >>> for PWM, which is what I tried in v7. > >> > >> When you say "must use specific channels", where is coming this > >> information ? > > > > If the backlight for the LCD is connected to the pin that corresponds > > to PWM1, then you must use the TCU channel 1. It's that simple. > > Is it a runtime detection or is it hardcoded somewhere ? > > (just trying to understand the whole picture) The PWM channel can be hardcoded in the "pwms" property of the clients. It can also be hardcoded in platform code, or simply requested from sysfs. > >>> I think we could find a way to use a devicetree property that > >>> doesn't trigger Rob. That would still be the easiest and cleanest > >>> solution. > >>> > >>> Maybe "ingenic,reserved-channels-mask", which would contain a > >>> mask of channels that can only be used by the timer driver. And > >>> what the timer driver does with these channels, would be specific > >>> to the implementation and would not appear in the bindings. I > >>> hope Rob can work with that. > >>> > >>> -Paul > > > -- > <http://www.linaro.org/> Linaro.org │ Open source software for ARM SoCs > > Follow Linaro: <http://www.facebook.com/pages/Linaro> Facebook | > <http://twitter.com/#!/linaroorg> Twitter | > <http://www.linaro.org/linaro-blog/> Blog >
