On 13/03/2017 16:18, Nicolas Ferre wrote: > Le 25/01/2017 à 16:11, Boris Brezillon a écrit : >> Hi Rob, >> >> Sorry to revive this old discussion, but there's still one aspect I'm >> not sure about. >> >> On Tue, 5 Jul 2016 10:40:22 -0500 >> Rob Herring <robh@xxxxxxxxxx> wrote: >> >>>>>> + - compatible: Should be "atmel,tcb-free-running-timer" >>>>>> + - reg: Should contain the TCB channels to be used. If the >>>>>> + counter width is 16 bits (at91rm9200-tcb), two consecutive >>>>>> + channels are needed. Else, only one channel will be used. >>>>>> + >>>>>> + * a clockevent device >>>>>> + - compatible: Should be "atmel,tcb-programmable-timer" >>>>> >>>>> This still looks like assigning usage in DT. As I'm willing to accept >>>>> that for PWM, either timer channels should be whatever channels are not >>>>> assigned to PWM (i.e. not in DT) or they should just be "timer" and let >>>>> the kernel decide their usage. >>>> >>>> I just reviewed Alexandre's new binding, and it makes the whole thing >>>> a lot more obscure: on older SoCs, we have to chain 2 channels to >>>> create an acceptable wraparound time (16 bits at 5MHz is generating too >>>> much interrupts to be acceptable). >>>> >>>> If we don't assign the mode from the DT, how should we know which >>>> channels should be chained to create the free-running timer? Note that >>>> not all channels can be chained together: they have to be part of the >>>> same timer counter block and have to be consecutive (0+1, 1+2 or 3+0). >>> >>> The driver can have this knowledge if it is just picking 2 consecutive >>> timers. It should already know it has 16-bit timers based on the >>> compatible string. If it gets more complicated then the features or >>> limitations of the channels should be listed so the driver can make a >>> choice. OMAP is a good example of lots of timers with differing >>> features. >> >> Yes it's possible to do that, but what about DT overlays then? Say you >> have some TCB channels you'd like to reserve because they are connected >> to pins that are exposed on your board. Those pins are not connected to >> any device yet, but extension boards can be added, and in this case you >> might want to expose new PWM devices by dynamically loading DT overlays. >> >> If your clksource/clkevent driver parsed the initial DT and picked X >> free channels randomly, it may conflicts with the one requested by the >> DT overlay. >> >> What's your solution for this case? > > It seems that we don't have any progress on this topic for more than 6 > months which is a pity as we now experience an issue that would have > been addressed completely by the TC rework [1]. > > aka "ping"... ;-) Hi Nicolas, Boris, is there any news from your side ? Thanks. -- Daniel -- <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 -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
