Re: [PATCH v9 4/4] gpu: nova-core: provide a clear error report for unsupported GPUs

[John Hubbard <jhubbard@nvidia.com>]

On 11/14/25 5:09 PM, John Hubbard wrote:
> Pass in a PCI device to Spec::new(), and provide a Display
> implementation for boot42, in order to provide a clear, concise report
> of what happened: the driver read NV_PMC_BOOT42, and found that the GPU
> is not supported.
> 
> For very old GPUs (older than Fermi), the driver still returns ENOTSUPP,

ENODEV, actually, now.


thanks,
-- 
John Hubbard

> but it does so without a driver-specific dmesg report. That is exactly
> appropriate, because if such a GPU is installed, it can only be
> supported by Nouveau. And if so, the user is not helped by additional
> error messages from Nova.
> 
> Here's the full dmesg output for a Blackwell (not yet supported) GPU:
> 
> NovaCore 0000:01:00.0: Probe Nova Core GPU driver.
> NovaCore 0000:01:00.0: Unsupported chipset: boot42 = 0x1b2a1000 (architecture 0x1b, implementation 0x2)
> NovaCore 0000:01:00.0: probe with driver NovaCore failed with error -524
> 
> Cc: Alexandre Courbot <acourbot@nvidia.com>
> Cc: Danilo Krummrich <dakr@kernel.org>
> Cc: Timur Tabi <ttabi@nvidia.com>
> Cc: Joel Fernandes <joelagnelf@nvidia.com>
> Signed-off-by: John Hubbard <jhubbard@nvidia.com>
> ---
>  drivers/gpu/nova-core/gpu.rs  |  9 ++++++---
>  drivers/gpu/nova-core/regs.rs | 18 ++++++++++++++++++
>  2 files changed, 24 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/nova-core/gpu.rs b/drivers/gpu/nova-core/gpu.rs
> index 8e04628ca3d9..2bbc084e2095 100644
> --- a/drivers/gpu/nova-core/gpu.rs
> +++ b/drivers/gpu/nova-core/gpu.rs
> @@ -191,7 +191,7 @@ pub(crate) struct Spec {
>  }
>  
>  impl Spec {
> -    fn new(bar: &Bar0) -> Result<Spec> {
> +    fn new(dev: &device::Device, bar: &Bar0) -> Result<Spec> {
>          // Some brief notes about boot0 and boot42, in chronological order:
>          //
>          // NV04 through NV50:
> @@ -216,7 +216,10 @@ fn new(bar: &Bar0) -> Result<Spec> {
>              return Err(ENODEV);
>          }
>  
> -        Spec::try_from(regs::NV_PMC_BOOT_42::read(bar))
> +        let boot42 = regs::NV_PMC_BOOT_42::read(bar);
> +        Spec::try_from(boot42).inspect_err(|_| {
> +            dev_err!(dev, "Unsupported chipset: {}\n", boot42);
> +        })
>      }
>  }
>  
> @@ -268,7 +271,7 @@ pub(crate) fn new<'a>(
>          bar: &'a Bar0,
>      ) -> impl PinInit<Self, Error> + 'a {
>          try_pin_init!(Self {
> -            spec: Spec::new(bar).inspect(|spec| {
> +            spec: Spec::new(pdev.as_ref(), bar).inspect(|spec| {
>                  dev_info!(pdev.as_ref(),"NVIDIA ({})\n", spec);
>              })?,
>  
> diff --git a/drivers/gpu/nova-core/regs.rs b/drivers/gpu/nova-core/regs.rs
> index c6e2e08c754b..a53b013f2eca 100644
> --- a/drivers/gpu/nova-core/regs.rs
> +++ b/drivers/gpu/nova-core/regs.rs
> @@ -67,6 +67,24 @@ pub(crate) fn chipset(self) -> Result<Chipset> {
>              })
>              .and_then(Chipset::try_from)
>      }
> +
> +    /// Returns the raw architecture value from the register.
> +    fn architecture_raw(self) -> u8 {
> +        ((self.0 >> Self::ARCHITECTURE_RANGE.start()) & ((1 << Self::ARCHITECTURE_RANGE.len()) - 1))
> +            as u8
> +    }
> +}
> +
> +impl kernel::fmt::Display for NV_PMC_BOOT_42 {
> +    fn fmt(&self, f: &mut kernel::fmt::Formatter<'_>) -> kernel::fmt::Result {
> +        write!(
> +            f,
> +            "boot42 = 0x{:08x} (architecture 0x{:x}, implementation 0x{:x})",
> +            self.0,
> +            self.architecture_raw(),
> +            self.implementation()
> +        )
> +    }
>  }
>  
>  // PBUS