lkml.org 
[lkml]   [2017]   [Jun]   [8]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH 46/58] clocksource/drivers: Add a new driver for the Atmel ARM TC blocks
    On Thu, Jun 08, 2017 at 09:59:01AM +0200, Alexandre Belloni wrote:
    > On 08/06/2017 at 09:44:46 +0200, Daniel Lezcano wrote:
    > >
    > > +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.
    > >
    >
    > Ok, so is the solution putting the driver back in mach-at91 were we can
    > do whatever we want like mach-omap2 is doing?

    No. And putting a driver in mach-<whatever> does not give the permission to do
    whatever you want. I won't tell you how OSS works, but moving code around or
    using another tree to circumvent a code review is just the best way to upset
    maintainers in general and hurt your karma.

    That said, I think you misunderstood my comment (or I was not clear). In the
    discussion given in the link above, I am in favor, somehow, to distinguish
    clockevent and clocksource to solve exactly what you are facing.

    Rob Herring told me it could be acceptable to have a property to tell if it is
    a clockevent or a clocksource.

    Mark Rutland disagreed on this.

    I was alone in the discussion, no consensus have been found.

    Now, you have a particular use case and I would like to resurrect the
    discussion in order to find a solution which can apply to all DT drivers.

    > > 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.belloni@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
    >
    > --
    > Alexandre Belloni, Free Electrons
    > Embedded Linux and Kernel engineering
    > http://free-electrons.com

    --

    <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

    \
     
     \ /
      Last update: 2017-06-12 01:23    [W:2.496 / U:0.144 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site