+Mark Rutland, +Rob Herring
Alexandre, Boris, have a look at https://www.spinics.net/lists/arm-kernel/msg572652.html That will tell you the story. On Thu, Jun 08, 2017 at 07:42:36AM +0200, Boris Brezillon wrote: > Le Thu, 8 Jun 2017 01:17:15 +0200, > Alexandre Belloni <alexandre.bell...@free-electrons.com> a écrit : > > > On 07/06/2017 at 23:08:48 +0200, Daniel Lezcano wrote: > > > > I was going to agree but this is not flexible enough because the > > > > quadrature decoder always uses the first two channels. So on some > > > > products, we may have: > > > > - TCB0: > > > > o channels 0,1: qdec > > > > o channel 2: clocksource > > > > > > > > - TCB1: > > > > o channels 0,1: qdec > > > > o channel 2: clockevent > > > > > > > > This avoids wasting TCB channels. > > > > > > Ok. In this case you can check if the interrupt is specified for the > > > node, if > > > yes, then it is a clockevent. > > > > > > > But currently it is always specified in the SoC's dtsi. I don't find > > that too practical to push that to the board's dts. Also, lying by > > omission (the IRQ is always wired) in the DT is not different from > > having a property selecting which timer is the clocksource and which is > > the clockevent. > > > > I agree with Alexandre here. Really, there's not much we can do to > detect which timer should be used as a clockevent and which one should > be used as a clocksource except explicitly specifying it in the DT. > Having an interrupt defined in one case (clockevent) and undefined in > the other case (clocksource), is just as hack-ish as the detection logic > Alexandre developed to avoid explicitly specifying the function > assigned to a specific timer. > > Can we please find a solution that makes everyone happy (DT, > clocksoure/clockevent and at91 maintainers)? > > How about adding a linux,timer-function property to specify which > function this timer is providing? > > Something like that for example: > > tcb0: timer@fff7c000 { > compatible = "atmel,at91rm9200-tcb", "simple-mfd", "syscon"; > #address-cells = <1>; > #size-cells = <0>; > reg = <0xfff7c000 0x100>; > interrupts = <18 4>; > clocks = <&tcb0_clk>, <&clk32k>; > clock-names = "t0_clk", "slow_clk"; > > timer@0 { > compatible = "atmel,tcb-timer"; > reg = <0>, <1>; > linux,timer-function = "clocksource"; > }; > > timer@2 { > compatible = "atmel,tcb-timer"; > reg = <2>; > linux,timer-function = "clockevent"; > }; > }; > > Alternatively, we could have a property or a node in chosen describing which > timer should be used: > > chosen { > clockevent { > timer = <&timer2>; > }; > > clocksource { > timer = <&timer0>; > }; > > /* > * or > * > * clockevent = <&timer2>; > * clocksource = <&timer0>; > * > * but I think the clocksource/clockevent node approach > * is more future proof in case we need to add extra > * information like the expected resolution/precision or > * anything that could be tweakable. > */ > }; > > tcb0: timer@fff7c000 { > compatible = "atmel,at91rm9200-tcb", "simple-mfd", "syscon"; > #address-cells = <1>; > #size-cells = <0>; > reg = <0xfff7c000 0x100>; > interrupts = <18 4>; > clocks = <&tcb0_clk>, <&clk32k>; > clock-names = "t0_clk", "slow_clk"; > > timer0: timer@0 { > compatible = "atmel,tcb-timer"; > reg = <0>, <1>; > }; > > timer2: timer@2 { > compatible = "atmel,tcb-timer"; > reg = <2>; > }; > }; -- <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
