[PATCH v2 7/7] riscv: Update SiFive device tree for new CLINT driver

[Anup Patel]

On Thu, Sep 3, 2020 at 4:23 PM Sean Anderson <seanga2 at gmail.com> wrote:
>
> On 9/3/20 1:01 AM, Anup Patel wrote:
> > On Thu, Sep 3, 2020 at 8:19 AM Bin Meng <bmeng.cn at gmail.com> wrote:
> >>
> >> Hi Anup,
> >>
> >> On Thu, Sep 3, 2020 at 10:46 AM Anup Patel <anup at brainfault.org> wrote:
> >>>
> >>> On Thu, Sep 3, 2020 at 7:32 AM Bin Meng <bmeng.cn at gmail.com> wrote:
> >>>>
> >>>> Hi Anup,
> >>>>
> >>>> On Tue, Aug 18, 2020 at 6:03 PM Sean Anderson <seanga2 at gmail.com> wrote:
> >>>>>
> >>>>> On 8/18/20 5:22 AM, Bin Meng wrote:
> >>>>>> +Anup Patel
> >>>>>>
> >>>>>> On Wed, Jul 29, 2020 at 5:57 PM Sean Anderson <seanga2 at gmail.com> wrote:
> >>>>>>>
> >>>>>>> We may need to add a clock-frequency binding like for the K210.
> >>>>>>>
> >>>>>>> Signed-off-by: Sean Anderson <seanga2 at gmail.com>
> >>>>>>> ---
> >>>>>>> This patch builds but has NOT been tested.
> >>>>>>>
> >>>>>>> Changes in v2:
> >>>>>>> - Fix SiFive CLINT not getting tick-rate from rtcclk
> >>>>>>>
> >>>>>>>  arch/riscv/dts/fu540-c000-u-boot.dtsi           | 8 ++++++--
> >>>>>>>  arch/riscv/dts/hifive-unleashed-a00-u-boot.dtsi | 4 ++++
> >>>>>>>  2 files changed, 10 insertions(+), 2 deletions(-)
> >>>>>>>
> >>>>>>> diff --git a/arch/riscv/dts/fu540-c000-u-boot.dtsi b/arch/riscv/dts/fu540-c000-u-boot.dtsi
> >>>>>>> index afdb4f4402..f126d3e0b3 100644
> >>>>>>> --- a/arch/riscv/dts/fu540-c000-u-boot.dtsi
> >>>>>>> +++ b/arch/riscv/dts/fu540-c000-u-boot.dtsi
> >>>>>>> @@ -53,9 +53,13 @@
> >>>>>>>                         reg = <0x0 0x10070000 0x0 0x1000>;
> >>>>>>>                         fuse-count = <0x1000>;
> >>>>>>>                 };
> >>>>>>> -               clint at 2000000 {
> >>>>>>> +               clint: clint at 2000000 {
> >>>>>>>                         compatible = "riscv,clint0";
> >>>>>>> -                       interrupts-extended = <&cpu0_intc 3 &cpu0_intc 7 &cpu1_intc 3 &cpu1_intc 7 &cpu2_intc 3 &cpu2_intc 7 &cpu3_intc 3 &cpu3_intc 7 &cpu4_intc 3 &cpu4_intc 7>;
> >>>>>>> +                       interrupts-extended = <&cpu0_intc 3 &cpu0_intc 7
> >>>>>>> +                                              &cpu1_intc 3 &cpu1_intc 7
> >>>>>>> +                                              &cpu2_intc 3 &cpu2_intc 7
> >>>>>>> +                                              &cpu3_intc 3 &cpu3_intc 7
> >>>>>>> +                                              &cpu4_intc 3 &cpu4_intc 7>;
> >>>>>>>                         reg = <0x0 0x2000000 0x0 0xc0000>;
> >>>>>>>                         u-boot,dm-spl;
> >>>>>>>                 };
> >>>>>>> diff --git a/arch/riscv/dts/hifive-unleashed-a00-u-boot.dtsi b/arch/riscv/dts/hifive-unleashed-a00-u-boot.dtsi
> >>>>>>> index e037150520..3275bb1f12 100644
> >>>>>>> --- a/arch/riscv/dts/hifive-unleashed-a00-u-boot.dtsi
> >>>>>>> +++ b/arch/riscv/dts/hifive-unleashed-a00-u-boot.dtsi
> >>>>>>> @@ -26,6 +26,10 @@
> >>>>>>>
> >>>>>>>  };
> >>>>>>>
> >>>>>>> +&clint {
> >>>>>>> +       clocks = <&rtcclk>;
> >>>>>>> +};
> >>>>>>
> >>>>>> Can we consider making this property a standard property by the kernel
> >>>>>> upstream? How does the kernel CLINT timer driver determine its running
> >>>>>> frequency?
> >>>>>
> >>>>> Currently it gets it from /cpus/timebase-frequency.
> >>>>
> >>>> What's your comment on this? I think this should go upstream to the
> >>>> standard bindings.
> >>>
> >>> My apologies for delay. Too many mailing list to track.
> >>>
> >>> I think "clocks" should be an optional DT property for CLINT driver (both
> >>> Linux and U-Boot). If "clocks" is not available then we should fallback to
> >>> "/cpus/timebase-frequency"
> >>>
> >>
> >> Agreed. The question is whether this should be mentioned in the DT
> >> bindings doc in the kernel tree?
> >
> > Yes, the "clocks" DT property should be updated in kernel DT bindings doc
> > and kernel CLINT driver should also prefer "clocks" DT property when available.
> >
> > Regards,
> > Anup
>
> Should clock-frequency be used as well, or should that be left for timebase-frequency?

Not sure about clock-frequency DT property. I think very few linux clocksource
drivers use "clock-frequency" DT property.

Probably it's fine to first check for "clocks" and "clock-frequency" before
falling back to "timebase-frequency".

Regards,
Anup

>
> --Sean