Re: [PATCH v4 11/20] gpu: nova-core: wait for GFW_BOOT completion

[Lyude Paul <lyude@redhat.com>]

On Wed, 2025-05-21 at 15:45 +0900, Alexandre Courbot wrote:
> Upon reset, the GPU executes the GFW (GPU Firmware) in order to
> initialize its base parameters such as clocks. The driver must ensure
> that this step is completed before using the hardware.
> 
> Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>
> ---
>  drivers/gpu/nova-core/gfw.rs       | 37 +++++++++++++++++++++++++++++++++++++
>  drivers/gpu/nova-core/gpu.rs       |  5 +++++
>  drivers/gpu/nova-core/nova_core.rs |  1 +
>  drivers/gpu/nova-core/regs.rs      | 25 +++++++++++++++++++++++++
>  drivers/gpu/nova-core/util.rs      |  1 -
>  5 files changed, 68 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/nova-core/gfw.rs b/drivers/gpu/nova-core/gfw.rs
> new file mode 100644
> index 0000000000000000000000000000000000000000..11ad480e1da826555e264101ef56ff0f69db8f95
> --- /dev/null
> +++ b/drivers/gpu/nova-core/gfw.rs
> @@ -0,0 +1,37 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +//! GPU Firmware (GFW) support.
> +//!
> +//! Upon reset, the GPU runs some firmware code from the BIOS to setup its core parameters. Most of
> +//! the GPU is considered unusable until this step is completed, so we must wait on it before
> +//! performing driver initialization.
> +
> +use core::time::Duration;
> +
> +use kernel::bindings;
> +use kernel::prelude::*;
> +
> +use crate::driver::Bar0;
> +use crate::regs;
> +use crate::util;
> +
> +/// Wait until GFW (GPU Firmware) completes, or a 4 seconds timeout elapses.
> +pub(crate) fn wait_gfw_boot_completion(bar: &Bar0) -> Result<()> {

JFYI: You can actually just say Result here, since () is the default type for
the kernel's Result type

> +    util::wait_on(Duration::from_secs(4), || {
> +        // Check that FWSEC has lowered its protection level before reading the GFW_BOOT
> +        // status.
> +        let gfw_booted = regs::NV_PGC6_AON_SECURE_SCRATCH_GROUP_05_PRIV_LEVEL_MASK::read(bar)
> +            .read_protection_level0()
> +            && regs::NV_PGC6_AON_SECURE_SCRATCH_GROUP_05_0_GFW_BOOT::read(bar).completed();
> +
> +        if gfw_booted {
> +            Some(())
> +        } else {
> +            // Avoid busy-looping.
> +            // SAFETY: msleep should be safe to call with any parameter.
> +            unsafe { bindings::msleep(1) };

TBH - we should really add some safe bindings for sleeps instead of calling
this unsafely, I'd be happy to review them if you do

> +
> +            None
> +        }
> +    })
> +}
> diff --git a/drivers/gpu/nova-core/gpu.rs b/drivers/gpu/nova-core/gpu.rs
> index 99c6796e73e924cb5fd2b6f49d84589c1ce5f627..50417f608dc7b445958ae43444a13c7593204fcf 100644
> --- a/drivers/gpu/nova-core/gpu.rs
> +++ b/drivers/gpu/nova-core/gpu.rs
> @@ -4,6 +4,7 @@
>  
>  use crate::driver::Bar0;
>  use crate::firmware::{Firmware, FIRMWARE_VERSION};
> +use crate::gfw;
>  use crate::regs;
>  use crate::util;
>  use core::fmt;
> @@ -182,6 +183,10 @@ pub(crate) fn new(
>              spec.revision
>          );
>  
> +        // We must wait for GFW_BOOT completion before doing any significant setup on the GPU.
> +        gfw::wait_gfw_boot_completion(bar)
> +            .inspect_err(|_| dev_err!(pdev.as_ref(), "GFW boot did not complete"))?;
> +
>          Ok(pin_init!(Self {
>              spec,
>              bar: devres_bar,
> diff --git a/drivers/gpu/nova-core/nova_core.rs b/drivers/gpu/nova-core/nova_core.rs
> index 618632f0abcc8f5ef6945a04fc084acc4ecbf20b..c3fde3e132ea658888851137ab47fcb7b3637577 100644
> --- a/drivers/gpu/nova-core/nova_core.rs
> +++ b/drivers/gpu/nova-core/nova_core.rs
> @@ -4,6 +4,7 @@
>  
>  mod driver;
>  mod firmware;
> +mod gfw;
>  mod gpu;
>  mod regs;
>  mod util;
> diff --git a/drivers/gpu/nova-core/regs.rs b/drivers/gpu/nova-core/regs.rs
> index 5a12732303066f78b8ec5745096cef632ff3bfba..cba442da51181971f209b338249307c11ac481e3 100644
> --- a/drivers/gpu/nova-core/regs.rs
> +++ b/drivers/gpu/nova-core/regs.rs
> @@ -37,3 +37,28 @@ pub(crate) fn chipset(self) -> Result<Chipset> {
>              .and_then(Chipset::try_from)
>      }
>  }
> +
> +/* PGC6 */
> +
> +register!(NV_PGC6_AON_SECURE_SCRATCH_GROUP_05_PRIV_LEVEL_MASK @ 0x00118128 {
> +    0:0     read_protection_level0 as bool, "Set after FWSEC lowers its protection level";
> +});
> +
> +// TODO: This is an array of registers.
> +register!(NV_PGC6_AON_SECURE_SCRATCH_GROUP_05 @ 0x00118234 {
> +    31:0    value as u32;
> +});
> +
> +register!(
> +    NV_PGC6_AON_SECURE_SCRATCH_GROUP_05_0_GFW_BOOT => NV_PGC6_AON_SECURE_SCRATCH_GROUP_05,
> +    "Scratch group 05 register 0 used as GFW boot progress indicator" {
> +        7:0    progress as u8, "Progress of GFW boot (0xff means completed)";
> +    }
> +);
> +
> +impl NV_PGC6_AON_SECURE_SCRATCH_GROUP_05_0_GFW_BOOT {
> +    /// Returns `true` if GFW boot is completed.
> +    pub(crate) fn completed(self) -> bool {
> +        self.progress() == 0xff
> +    }
> +}
> diff --git a/drivers/gpu/nova-core/util.rs b/drivers/gpu/nova-core/util.rs
> index afb525228431a2645afe7bb34988e9537757b1d7..81fcfff1f6f437d2f6a2130ce2249fbf4c1501be 100644
> --- a/drivers/gpu/nova-core/util.rs
> +++ b/drivers/gpu/nova-core/util.rs
> @@ -34,7 +34,6 @@ pub(crate) const fn const_bytes_to_str(bytes: &[u8]) -> &str {
>  ///
>  /// TODO: replace with `read_poll_timeout` once it is available.
>  /// (https://lore.kernel.org/lkml/20250220070611.214262-8-fujita.tomonori@gmail.com/)
> -#[expect(dead_code)]
>  pub(crate) fn wait_on<R, F: Fn() -> Option<R>>(timeout: Duration, cond: F) -> Result<R> {
>      let start_time = Ktime::ktime_get();
>  
> 

-- 
Cheers,
 Lyude Paul (she/her)
 Software Engineer at Red Hat

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