Re: [PATCH 4/6] gpu: nova-core: add FbHal::frts_size() for GA100 support

["Alexandre Courbot" <acourbot@nvidia.com>]

On Sat Apr 11, 2026 at 5:37 AM JST, Timur Tabi wrote:
> Introduce FbHal method frts_size() to return the size of the FRTS
> window.  GA100 is a special case in that there is no FRTS, and so
> the size must be set to 0.
>
> Note that we cannot use supports_display() to determine the FRTS
> size because there are other GPUs (e.g. GA102GL) that have display
> disabled (and so supports_display() returns False), but the FRTS
> window size still needs to be 1MB.

Order-wise this should probably come before patch 3 - I was a bit
confused about the fact that we are checking the size of the frts region
since it is defined as a constant until this patch.

>
> Signed-off-by: Timur Tabi <ttabi@nvidia.com>
> ---
>  drivers/gpu/nova-core/fb.rs           | 6 +++---
>  drivers/gpu/nova-core/fb/hal.rs       | 3 +++
>  drivers/gpu/nova-core/fb/hal/ga100.rs | 5 +++++
>  drivers/gpu/nova-core/fb/hal/ga102.rs | 8 +++++++-
>  drivers/gpu/nova-core/fb/hal/tu102.rs | 8 +++++++-
>  5 files changed, 25 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/gpu/nova-core/fb.rs b/drivers/gpu/nova-core/fb.rs
> index bdd5eed760e1..abffc21427a1 100644
> --- a/drivers/gpu/nova-core/fb.rs
> +++ b/drivers/gpu/nova-core/fb.rs
> @@ -216,10 +216,10 @@ pub(crate) fn new(chipset: Chipset, bar: &Bar0, gsp_fw: &GspFirmware) -> Result<
>  
>          let frts = {
>              const FRTS_DOWN_ALIGN: Alignment = Alignment::new::<SZ_128K>();
> -            const FRTS_SIZE: u64 = usize_as_u64(SZ_1M);
> -            let frts_base = vga_workspace.start.align_down(FRTS_DOWN_ALIGN) - FRTS_SIZE;
> +            let frts_size: u64 = hal.frts_size();
> +            let frts_base = vga_workspace.start.align_down(FRTS_DOWN_ALIGN) - frts_size;
>  
> -            FbRange(frts_base..frts_base + FRTS_SIZE)
> +            FbRange(frts_base..frts_base + frts_size)
>          };
>  
>          let boot = {
> diff --git a/drivers/gpu/nova-core/fb/hal.rs b/drivers/gpu/nova-core/fb/hal.rs
> index aba0abd8ee00..1c01a6cbed65 100644
> --- a/drivers/gpu/nova-core/fb/hal.rs
> +++ b/drivers/gpu/nova-core/fb/hal.rs
> @@ -25,6 +25,9 @@ pub(crate) trait FbHal {
>  
>      /// Returns the VRAM size, in bytes.
>      fn vidmem_size(&self, bar: &Bar0) -> u64;
> +
> +    /// Returns the FRTS size, in bytes.
> +    fn frts_size(&self) -> u64;
>  }
>  
>  /// Returns the HAL corresponding to `chipset`.
> diff --git a/drivers/gpu/nova-core/fb/hal/ga100.rs b/drivers/gpu/nova-core/fb/hal/ga100.rs
> index 1c03783cddef..0e7d91fbd130 100644
> --- a/drivers/gpu/nova-core/fb/hal/ga100.rs
> +++ b/drivers/gpu/nova-core/fb/hal/ga100.rs
> @@ -66,6 +66,11 @@ fn supports_display(&self, bar: &Bar0) -> bool {
>      fn vidmem_size(&self, bar: &Bar0) -> u64 {
>          super::tu102::vidmem_size_gp102(bar)
>      }
> +
> +    // GA100 is a special case where it has no FRTS.
> +    fn frts_size(&self) -> u64 {
> +        0
> +    }
>  }
>  
>  const GA100: Ga100 = Ga100;
> diff --git a/drivers/gpu/nova-core/fb/hal/ga102.rs b/drivers/gpu/nova-core/fb/hal/ga102.rs
> index 4b9f0f74d0e7..167d38e34370 100644
> --- a/drivers/gpu/nova-core/fb/hal/ga102.rs
> +++ b/drivers/gpu/nova-core/fb/hal/ga102.rs
> @@ -2,12 +2,14 @@
>  
>  use kernel::{
>      io::Io,
> -    prelude::*, //
> +    prelude::*,
> +    sizes::*, //
>  };
>  
>  use crate::{
>      driver::Bar0,
>      fb::hal::FbHal,
> +    num::*,
>      regs, //
>  };
>  
> @@ -35,6 +37,10 @@ fn supports_display(&self, bar: &Bar0) -> bool {
>      fn vidmem_size(&self, bar: &Bar0) -> u64 {
>          vidmem_size_ga102(bar)
>      }
> +
> +    fn frts_size(&self) -> u64 {
> +        usize_as_u64(SZ_1M)
> +    }

This implementation is identical to the one in `tu102.rs`. As a pattern,
when different HALs use different implementations, we define it into a
function that both HALs can call instead of repeating the code (see for
instance how `read_sysmem_flush_page` is handled between ga100 and
ga102).