[PATCH v2 2/2] lib: utils/timer: mtimer: add MIPS P8700 compatible

[Anup Patel]

On Thu, Nov 6, 2025 at 2:58 PM Benoît Monin <benoit.monin at bootlin.com> wrote:
>
> Hi Anup,
>
> On Wednesday, 5 November 2025 at 17:11:11 CET, Anup Patel wrote:
> > On Mon, Oct 27, 2025 at 6:42 PM Benoît Monin <benoit.monin at bootlin.com> wrote:
> > >
> > > The MTIMER of the MIPS P8700 is compliant with the ACLINT specification,
> > > so add a compatible string for it.
> > >
> > > In a multi-cluster configuration, there is one MTIMER per cluster, each
> > > associated with the HARTS of the cluster. So we do not have a MTIMER
> > > with no associated HARTs to use as our reference.
> > >
> > > To be able to select a reference MTIMER in that case, add a quirk to look
> > > up an optional device tree property that indicate which MTIMER to use.
> > > For the MIPS P8700, the property is "mips,reference-mtimer".
> > >
> > > Signed-off-by: Benoît Monin <benoit.monin at bootlin.com>
> > > ---
> > >  lib/utils/timer/fdt_timer_mtimer.c | 25 +++++++++++++++++++------
> > >  1 file changed, 19 insertions(+), 6 deletions(-)
> > >
> > > diff --git a/lib/utils/timer/fdt_timer_mtimer.c b/lib/utils/timer/fdt_timer_mtimer.c
> > > index e1fd051..e98c99f 100644
> > > --- a/lib/utils/timer/fdt_timer_mtimer.c
> > > +++ b/lib/utils/timer/fdt_timer_mtimer.c
> > > @@ -20,6 +20,7 @@ struct timer_mtimer_quirks {
> > >         unsigned int    clint_mtime_offset;
> > >         bool            clint_without_mtime;
> > >         bool            has_64bit_mmio;
> > > +       const char      *dt_ref_prop;
> > >  };
> > >
> > >  struct timer_mtimer_node {
> > > @@ -39,6 +40,7 @@ static int timer_mtimer_cold_init(const void *fdt, int nodeoff,
> > >         struct aclint_mtimer_data *mt;
> > >         const struct timer_mtimer_quirks *quirks = match->data;
> > >         bool is_clint = quirks && quirks->is_clint;
> > > +       bool is_ref = false;
> > >
> > >         mtn = sbi_zalloc(sizeof(*mtn));
> > >         if (!mtn)
> > > @@ -110,13 +112,18 @@ static int timer_mtimer_cold_init(const void *fdt, int nodeoff,
> > >         }
> > >
> > >         /*
> > > -        * Select first MTIMER device with no associated HARTs as our
> > > -        * reference MTIMER device. This is only a temporary strategy
> > > -        * of selecting reference MTIMER device. In future, we might
> > > -        * define an optional DT property or some other mechanism to
> > > -        * help us select the reference MTIMER device.
> > > +        * If we have a DT property to indicate which MTIMER is the reference,
> > > +        * select the first MTIMER device that has it. Otherwise, select the
> > > +        * first MTIMER device with no associated HARTs as our reference.
> > >          */
> > > -       if (!mt->hart_count && !mt_reference) {
> > > +       if (quirks && quirks->dt_ref_prop) {
> > > +               if (fdt_getprop(fdt, nodeoff, quirks->dt_ref_prop, NULL))
> > > +                       is_ref = true;
> > > +       } else if (!mt->hart_count) {
> > > +               is_ref = true;
> > > +       }
> > > +
> > > +       if (is_ref && !mt_reference) {
> > >                 mt_reference = mt;
> > >                 /*
> > >                  * Set reference for already propbed MTIMER devices
> > > @@ -152,6 +159,10 @@ static const struct timer_mtimer_quirks thead_aclint_quirks = {
> > >         .has_64bit_mmio         = false,
> > >  };
> > >
> > > +static const struct timer_mtimer_quirks mips_aclint_quirks = {
> > > +       .dt_ref_prop            = "mips,reference-mtimer",
> > > +};
> > > +
> >
> > I think this DT property can be useful to other platforms as well.
> > How about "riscv,reference-mtimer" as a DT property ? This way
> > you don't need to make it as MIPS quirk.
> >
> ACLINT is not a ratified specification, is it okay to use the "riscv,"
> prefix? That's the reason I went with a vendor prefix.
>

It's unfortunate that ACLINT was not ratified but nevertheless it
is a RISC-V draft specification and at this point quite a few RISC-V
platforms have at least implemented the mtimer part of the ACLINT.

Regards,
Anup