Re: [PATCH v10 08/28] gpu: nova-core: Blackwell: calculate reserved FB heap size

Gary Guo
2026-04-20T16:20:50Z

On Sat Apr 11, 2026 at 3:49 AM BST, John Hubbard wrote:
> Various "reserved" areas of FB (frame buffer: vidmem) have to be
> calculated, because the GSP booting process needs this information.
>
> PMU_RESERVED_SIZE is computed at compile time using const_align_up() and
> applied only for Blackwell dGPU architectures. All other architectures
> leave it at zero, matching Open RM behavior.
>
> Signed-off-by: John Hubbard <jhubbard@nvidia.com>
> ---
> drivers/gpu/nova-core/fb.rs | 38 ++++++++++++++++++++++++++++++---
> drivers/gpu/nova-core/gsp/fw.rs | 1 +
> 2 files changed, 36 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/nova-core/fb.rs b/drivers/gpu/nova-core/fb.rs
> index 35899e9b2560..c2005e4b4177 100644
> --- a/drivers/gpu/nova-core/fb.rs
> +++ b/drivers/gpu/nova-core/fb.rs
> @@ -12,6 +12,7 @@
> io::Io,
> prelude::*,
> ptr::{
> + const_align_up,
> Alignable,
> Alignment, //
> },
> @@ -22,10 +23,16 @@
> use crate::{
> driver::Bar0,
> firmware::gsp::GspFirmware,
> - gpu::Chipset,
> + gpu::{
> + Architecture,
> + Chipset, //
> + },
> gsp,
> - num::FromSafeCast,
> - regs, //
> + num::{
> + usize_into_u32,
> + FromSafeCast, //
> + },
> + regs,
> };
>
> mod hal;
> @@ -168,6 +175,8 @@ pub(crate) struct FbLayout {
> pub(crate) wpr2: FbRange,
> pub(crate) heap: FbRange,
> pub(crate) vf_partition_count: u8,
> + /// PMU reserved memory size, in bytes.
> + pub(crate) pmu_reserved_size: u32,
> }
>
> impl FbLayout {
> @@ -268,6 +277,29 @@ pub(crate) fn new(chipset: Chipset, bar: &Bar0, gsp_fw: &GspFirmware) -> Result<
> wpr2,
> heap,
> vf_partition_count: 0,
> + pmu_reserved_size: match chipset.arch() {
> + Architecture::BlackwellGB10x | Architecture::BlackwellGB20x => PMU_RESERVED_SIZE,
> + _ => 0,
> + },
> })
> }
> }
> +
> +/// Returns the PMU reserved memory size for `chipset`.
> +#[expect(dead_code)]
> +pub(crate) fn calc_pmu_reserved_size(chipset: Chipset) -> u32 {
> + match chipset.arch() {
> + Architecture::BlackwellGB10x | Architecture::BlackwellGB20x => PMU_RESERVED_SIZE,
> + _ => 0,
> + }
> +}
> +
> +/// PMU reserved size, aligned to 128KB.
> +pub(crate) const PMU_RESERVED_SIZE: u32 = usize_into_u32::<
> + {
> + match const_align_up(SZ_8M + SZ_16M + SZ_4K, Alignment::new::<SZ_128K>()) {
> + Some(v) => v,
> + None => panic!("PMU_RESERVED_SIZE: alignment overflow"),
> + }
> + },
> +>();

You may use `.unwrap()` now as MSRV has been bumped to 1.85.

(Technically, you could have used it earlier by adding it to list of allowed
features, too)

Best,
Gary

> diff --git a/drivers/gpu/nova-core/gsp/fw.rs b/drivers/gpu/nova-core/gsp/fw.rs
> index 3245793bbe42..5d36604ea1a3 100644
> --- a/drivers/gpu/nova-core/gsp/fw.rs
> +++ b/drivers/gpu/nova-core/gsp/fw.rs
> @@ -247,6 +247,7 @@ pub(crate) fn new<'a>(
> fbSize: fb_layout.fb.end - fb_layout.fb.start,
> vgaWorkspaceOffset: fb_layout.vga_workspace.start,
> vgaWorkspaceSize: fb_layout.vga_workspace.end - fb_layout.vga_workspace.start,
> + pmuReservedSize: fb_layout.pmu_reserved_size,
> ..Zeroable::init_zeroed()
> });
>