Nouveau - Sep 2025 - [PATCH 08/10] gpu: nova-core: falcon: Add support to check if RISC-V is active

From: Joel Fernandes <joelagnelf at nvidia.com>

Add definition for RISCV_CPUCTL register and use it in a new falcon API
to check if the RISC-V core of a Falcon is active. It is required by
the sequencer to know if the GSP's RISCV processor is active.

Signed-off-by: Joel Fernandes <joelagnelf at nvidia.com>
---
 drivers/gpu/nova-core/falcon.rs | 8 ++++++++
 drivers/gpu/nova-core/regs.rs   | 5 +++++
 2 files changed, 13 insertions(+)

diff --git a/drivers/gpu/nova-core/falcon.rs b/drivers/gpu/nova-core/falcon.rs
index 7bd13481a6a37..8c4faff043455 100644
--- a/drivers/gpu/nova-core/falcon.rs
+++ b/drivers/gpu/nova-core/falcon.rs
@@ -610,4 +610,12 @@ pub(crate) fn signature_reg_fuse_version(
         self.hal
             .signature_reg_fuse_version(self, bar, engine_id_mask, ucode_id)
     }
+
+    /// Check if the RISC-V core is active.
+    ///
+    /// Returns `true` if the RISC-V core is active, `false` otherwise.
+    pub(crate) fn is_riscv_active(&self, bar: &Bar0) ->
Result<bool> {
+        let cpuctl = regs::NV_PRISCV_RISCV_CPUCTL::read(bar, &E::ID);
+        Ok(cpuctl.active_stat())
+    }
 }
diff --git a/drivers/gpu/nova-core/regs.rs b/drivers/gpu/nova-core/regs.rs
index 0585699ae9511..5df6a2bf42ad9 100644
--- a/drivers/gpu/nova-core/regs.rs
+++ b/drivers/gpu/nova-core/regs.rs
@@ -324,6 +324,11 @@ pub(crate) fn mem_scrubbing_done(self) -> bool {
 
 // PRISCV
 
+register!(NV_PRISCV_RISCV_CPUCTL @ PFalconBase[0x00001388] {
+    7:7     active_stat as bool;
+    0:0     halted as bool;
+});
+
 register!(NV_PRISCV_RISCV_BCR_CTRL @ PFalconBase[0x00001668] {
     0:0     valid as bool;
     4:4     core_select as bool => PeregrineCoreSelect;
-- 
2.47.2

On Wed, 2025-08-27 at 18:20 +1000, Alistair Popple
wrote:
> +??? pub(crate) fn is_riscv_active(&self, bar: &Bar0) ->
Result<bool> {
> +??????? let cpuctl = regs::NV_PRISCV_RISCV_CPUCTL::read(bar, &E::ID);
> +??????? Ok(cpuctl.active_stat())
> +??? }
I think this should return just bool instead of Result<bool>

On 2025-08-30 at 04:48 +1000, Timur Tabi <ttabi at nvidia.com>
wrote...
> On Wed, 2025-08-27 at 18:20 +1000, Alistair Popple wrote:
> > +??? pub(crate) fn is_riscv_active(&self, bar: &Bar0) ->
Result<bool> {
> > +??????? let cpuctl = regs::NV_PRISCV_RISCV_CPUCTL::read(bar,
&E::ID);
> > +??????? Ok(cpuctl.active_stat())
> > +??? }
> 
> I think this should return just bool instead of Result<bool>
Agreed. And looking at some of the other sequencer/falcon code in Joel's
series
I believe similar comments apply there. I assume something changed with the
register reading code to make this possible.

On Wed, Aug 27, 2025 at 3:28?AM Alistair Popple <apopple at nvidia.com>
wrote:
>
> +register!(NV_PRISCV_RISCV_CPUCTL @ PFalconBase[0x00001388] {
> +    7:7     active_stat as bool;
> +    0:0     halted as bool;
> +});
Two more things I've noticed:

1) I think the convention is to list the bits in increase position.
That is, 'active_stat' should be on the line below 'halted''

2) I think that this should actually be PFalcon2Base[0x00000388]