[PATCH v2 0/2] Add MIPS P8700 compatibles for ACLINT MSWI and MTIMER

[PATCH v2 0/2] Add MIPS P8700 compatibles for ACLINT MSWI and MTIMER

[Benoît Monin]

The ACLINT found in the MIPS P8700 is compliant with the now archived
RISC-V Advanced Core Local Interruptor Specification. There is one
ACLINT controller per cluster, as part of what MIPS calls the coherence
manager.

The MSWI does not require any changes in the code, so only a compatible
string is added.

For the MTIMER, there is no dedicated mtime register to act a reference
in a multi-cluster configuration, and there is no MTIMER without
associated HARTs. A quirk is added to select the reference MTIMER based
on a device tree property.

Signed-off-by: Benoît Monin <benoit.monin@bootlin.com>
---
Changes in v2:
- Select the reference MTIMER based on a DT property, not the first one
  found.
- Link to v1: https://lore.kernel.org/r/20251009-p8700-aclint-v1-0-18322c64f968@bootlin.com

---
Benoît Monin (2):
      lib: utils/ipi: mswi: add MIPS P8700 compatible
      lib: utils/timer: mtimer: add MIPS P8700 compatible

 lib/utils/ipi/fdt_ipi_mswi.c       |  1 +
 lib/utils/timer/fdt_timer_mtimer.c | 25 +++++++++++++++++++------
 2 files changed, 20 insertions(+), 6 deletions(-)
---
base-commit: ac16c6b604961525bb096c0513c6ad4dbf5a5695
change-id: 20251008-p8700-aclint-ef8868889745

Best regards,
-- 
Benoît Monin, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com


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[PATCH v2 1/2] lib: utils/ipi: mswi: add MIPS P8700 compatible

[Benoît Monin]

The MSWI present in the MIPS P8700 is compliant with the ACLINT
specification, so add a dedicated compatible string for it.

Signed-off-by: Benoît Monin <benoit.monin@bootlin.com>
---
 lib/utils/ipi/fdt_ipi_mswi.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/lib/utils/ipi/fdt_ipi_mswi.c b/lib/utils/ipi/fdt_ipi_mswi.c
index 20f6fbc..6d8f6bf 100644
--- a/lib/utils/ipi/fdt_ipi_mswi.c
+++ b/lib/utils/ipi/fdt_ipi_mswi.c
@@ -57,6 +57,7 @@ static const struct fdt_match ipi_mswi_match[] = {
 	{ .compatible = "sifive,clint0", .data = &clint_offset },
 	{ .compatible = "thead,c900-clint", .data = &clint_offset },
 	{ .compatible = "thead,c900-aclint-mswi" },
+	{ .compatible = "mips,p8700-aclint-mswi" },
 	{ .compatible = "riscv,aclint-mswi" },
 	{ },
 };

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Re: [PATCH v2 1/2] lib: utils/ipi: mswi: add MIPS P8700 compatible

[Anup Patel]

On Mon, Oct 27, 2025 at 6:42 PM Benoît Monin <benoit.monin@bootlin.com> wrote:
>
> The MSWI present in the MIPS P8700 is compliant with the ACLINT
> specification, so add a dedicated compatible string for it.
>
> Signed-off-by: Benoît Monin <benoit.monin@bootlin.com>

LGTM.

Reviewed-by: Anup Patel <anup@brainfault.org>

Applied this patch to the riscv/opensbi repo.

Thanks,
Anup

> ---
>  lib/utils/ipi/fdt_ipi_mswi.c | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/lib/utils/ipi/fdt_ipi_mswi.c b/lib/utils/ipi/fdt_ipi_mswi.c
> index 20f6fbc..6d8f6bf 100644
> --- a/lib/utils/ipi/fdt_ipi_mswi.c
> +++ b/lib/utils/ipi/fdt_ipi_mswi.c
> @@ -57,6 +57,7 @@ static const struct fdt_match ipi_mswi_match[] = {
>         { .compatible = "sifive,clint0", .data = &clint_offset },
>         { .compatible = "thead,c900-clint", .data = &clint_offset },
>         { .compatible = "thead,c900-aclint-mswi" },
> +       { .compatible = "mips,p8700-aclint-mswi" },
>         { .compatible = "riscv,aclint-mswi" },
>         { },
>  };
>
> --
> 2.51.1
>
>
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[PATCH v2 2/2] lib: utils/timer: mtimer: add MIPS P8700 compatible

[Benoît Monin]

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@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",
+};
+
 static const struct fdt_match timer_mtimer_match[] = {
 	{ .compatible = "riscv,clint0", .data = &sifive_clint_quirks },
 	{ .compatible = "sifive,clint0", .data = &sifive_clint_quirks },
@@ -159,6 +170,8 @@ static const struct fdt_match timer_mtimer_match[] = {
 	{ .compatible = "thead,c900-clint", .data = &thead_clint_quirks },
 	{ .compatible = "thead,c900-aclint-mtimer",
 	  .data = &thead_aclint_quirks },
+	{ .compatible = "mips,p8700-aclint-mtimer",
+	  .data = &mips_aclint_quirks },
 	{ .compatible = "riscv,aclint-mtimer" },
 	{ },
 };

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

[Anup Patel]

On Mon, Oct 27, 2025 at 6:42 PM Benoît Monin <benoit.monin@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@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.

>  static const struct fdt_match timer_mtimer_match[] = {
>         { .compatible = "riscv,clint0", .data = &sifive_clint_quirks },
>         { .compatible = "sifive,clint0", .data = &sifive_clint_quirks },
> @@ -159,6 +170,8 @@ static const struct fdt_match timer_mtimer_match[] = {
>         { .compatible = "thead,c900-clint", .data = &thead_clint_quirks },
>         { .compatible = "thead,c900-aclint-mtimer",
>           .data = &thead_aclint_quirks },
> +       { .compatible = "mips,p8700-aclint-mtimer",
> +         .data = &mips_aclint_quirks },
>         { .compatible = "riscv,aclint-mtimer" },
>         { },
>  };
>
> --
> 2.51.1
>
>
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Regards,
Anup

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

[Benoît Monin]

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@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@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.

[...]

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Re: [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@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@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@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

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