Re: [PATCH v2 5/6] gpu: nova-core: skip the IFR header if present

["Gary Guo" <gary@garyguo.net>]

On Wed Apr 15, 2026 at 12:50 AM BST, Timur Tabi wrote:
> The GPU's ROM may begin with an Init-from-ROM (IFR) header that precedes
> the PCI Expansion ROM images (VBIOS).  When present, the PROM shadow
> method must parse this header to determine the offset where the PCI ROM
> images actually begin, and adjust all subsequent reads accordingly.
>
> On most GPUs this is not needed because the IFR microcode has already
> applied the ROM offset so that PROM reads transparently skip the header.
> On GA100, for whatever reason, the IFR offset is not applied to PROM
> reads.  Therefore, the search for the PCI expansion must skip the IFR
> header, if found.
>
> Signed-off-by: Timur Tabi <ttabi@nvidia.com>
> ---
>  drivers/gpu/nova-core/vbios.rs | 67 +++++++++++++++++++++++++++++++++-
>  1 file changed, 66 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/nova-core/vbios.rs b/drivers/gpu/nova-core/vbios.rs
> index e726594eb130..000e823b9e47 100644
> --- a/drivers/gpu/nova-core/vbios.rs
> +++ b/drivers/gpu/nova-core/vbios.rs
> @@ -89,13 +89,78 @@ struct VbiosIterator<'a> {
>      last_found: bool,
>  }
>  
> +/// Offset of FIXED0 field in IFR header
> +const NV_PBUS_IFR_FMT_FIXED0: usize = 0x00000000;
> +/// Offset of FIXED1 field in IFR header
> +const NV_PBUS_IFR_FMT_FIXED1: usize = 0x00000004;
> +/// Offset of FIXED2 field in IFR header
> +const NV_PBUS_IFR_FMT_FIXED2: usize = 0x00000008;
> +/// IFR signature: ASCII "NVGI" as a little-endian u32.
> +const NV_PBUS_IFR_FMT_FIXED0_SIGNATURE_VALUE: u32 = 0x4947564E;
> +/// ROM directory signature: ASCII "RFRD" as a little-endian u32.
> +const NV_ROM_DIRECTORY_IDENTIFIER: u32 = 0x44524652;
> +/// Offset of the NV_PMGR_ROM_ADDR_OFFSET register in IFR Extended section
> +const IFR_SW_EXT_ROM_ADDR_OFFSET: usize = 4;
> +/// Size of Redundant Firmware Flash Status section
> +const RFW_FLASH_STATUS_SIZE: usize = 4096;
> +
> +bitfield! {
> +    struct IfrFixed1(u32) {
> +        15:8 version as u8;
> +        30:16 fixed_data_size as u16;
> +    }
> +}
> +
> +bitfield! {
> +    struct IfrFixed2(u32) {
> +        19:0 total_data_size as u32;
> +    }
> +}

Shouldn't this be using the `register!` macro instead?

Best,
Gary

> +
>  impl<'a> VbiosIterator<'a> {
>      fn new(dev: &'a device::Device, bar0: &'a Bar0) -> Result<Self> {
> +        let signature = bar0.try_read32(ROM_OFFSET + NV_PBUS_IFR_FMT_FIXED0)?;
> +
> +        // The ROM may start with an Init-from-ROM (IFR) header before the PCI
> +        // Expansion ROM images. Most GPUs apply the IFR offset transparently, but
> +        // GA100 does not, so we must skip the header manually if present.
> +
> +        let current_offset = if signature == NV_PBUS_IFR_FMT_FIXED0_SIGNATURE_VALUE {
> +            let fixed1 = IfrFixed1(bar0.try_read32(ROM_OFFSET + NV_PBUS_IFR_FMT_FIXED1)?);
> +
> +            match fixed1.version() {
> +                // Note: We do not actually expect to see v1 or v2 on these GPUs
> +                1 | 2 => {
> +                    let fixed_data_size = fixed1.fixed_data_size() as usize;
> +                    let pmgr_rom_addr_offset = fixed_data_size + IFR_SW_EXT_ROM_ADDR_OFFSET;
> +                    bar0.try_read32(ROM_OFFSET + pmgr_rom_addr_offset)? as usize
> +                }
> +                3 => {
> +                    let fixed2 = IfrFixed2(bar0.try_read32(ROM_OFFSET + NV_PBUS_IFR_FMT_FIXED2)?);
> +                    let total_data_size = fixed2.total_data_size() as usize;
> +                    let dir_offset = bar0.try_read32(ROM_OFFSET + total_data_size)? as usize
> +                        + RFW_FLASH_STATUS_SIZE;
> +                    let dir_sig = bar0.try_read32(ROM_OFFSET + dir_offset)?;
> +                    if dir_sig != NV_ROM_DIRECTORY_IDENTIFIER {
> +                        dev_err!(dev, "could not find IFR ROM directory\n");
> +                        return Err(EINVAL);
> +                    }
> +                    bar0.try_read32(ROM_OFFSET + dir_offset + 8)? as usize
> +                }
> +                _ => {
> +                    dev_err!(dev, "unsupported IFR header version {}\n", fixed1.version());
> +                    return Err(EINVAL);
> +                }
> +            }
> +        } else {
> +            0
> +        };
> +
>          Ok(Self {
>              dev,
>              bar0,
>              data: KVec::new(),
> -            current_offset: 0,
> +            current_offset,
>              last_found: false,
>          })
>      }