[PATCH v5 5/6] gpu: nova-core: skip the IFR header if present

Timur Tabi
2026-04-17T19:14:39Z

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 | 85 +++++++++++++++++++++++++++++++++-
1 file changed, 84 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/nova-core/vbios.rs b/drivers/gpu/nova-core/vbios.rs
index e726594eb130..6bcfb6c5cf44 100644
--- a/drivers/gpu/nova-core/vbios.rs
+++ b/drivers/gpu/nova-core/vbios.rs
@@ -12,6 +12,8 @@
Alignable,
Alignment, //
},
+ register,
+ sizes::SZ_4K,
sync::aref::ARef,
transmute::FromBytes,
};
@@ -89,13 +91,94 @@ struct VbiosIterator<'a> {
last_found: bool,
}

+// IFR Header in VBIOS.
+
+register! {
+ pub(crate) NV_PBUS_IFR_FMT_FIXED0(u32) @ 0x300000 {
+ 31:0 signature;
+ }
+}
+
+register! {
+ pub(crate) NV_PBUS_IFR_FMT_FIXED1(u32) @ 0x300004 {
+ 30:16 fixed_data_size;
+ 15:8 version => u8;
+ }
+}
+
+register! {
+ pub(crate) NV_PBUS_IFR_FMT_FIXED2(u32) @ 0x300008 {
+ 19:0 total_data_size;
+ }
+}
+
+/// Return the byte offset where the PCI Expansion ROM images begin in the GPU's ROM.
+///
+/// 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 some reason, the IFR offset is not applied to PROM
+/// reads. Therefore, the search for the PCI expansion must skip the IFR
+/// header, if found.
+fn vbios_rom_offset(dev: &device::Device, bar0: &Bar0) -> Result<usize> {
+ /// IFR signature.
+ const NV_PBUS_IFR_FMT_FIXED0_SIGNATURE_VALUE: u32 = u32::from_le_bytes(*b"NVGI");
+ /// ROM directory signature.
+ const NV_ROM_DIRECTORY_IDENTIFIER: u32 = u32::from_le_bytes(*b"RFRD");
+ /// 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 = SZ_4K;
+ /// Offset in the ROM Directory of the PCI Option ROM offset
+ const PCI_OPTION_ROM_OFFSET: usize = 8;
+
+ let signature = bar0.read(NV_PBUS_IFR_FMT_FIXED0).signature();
+
+ if signature == NV_PBUS_IFR_FMT_FIXED0_SIGNATURE_VALUE {
+ let fixed1 = bar0.read(NV_PBUS_IFR_FMT_FIXED1);
+
+ match fixed1.version() {
+ 1 | 2 => {
+ let fixed_data_size = usize::from(fixed1.fixed_data_size());
+ let pmgr_rom_addr_offset = fixed_data_size + IFR_SW_EXT_ROM_ADDR_OFFSET;
+ bar0.try_read32(ROM_OFFSET + pmgr_rom_addr_offset)
+ .map(usize::from_safe_cast)
+ }
+ 3 => {
+ let fixed2 = bar0.read(NV_PBUS_IFR_FMT_FIXED2);
+ let total_data_size = usize::from(fixed2.total_data_size());
+ let flash_status_offset =
+ usize::from_safe_cast(bar0.try_read32(ROM_OFFSET + total_data_size)?);
+ let dir_offset = flash_status_offset + 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 + PCI_OPTION_ROM_OFFSET)
+ .map(usize::from_safe_cast)
+ }
+ _ => {
+ dev_err!(dev, "unsupported IFR header version {}\n", fixed1.version());
+ Err(EINVAL)
+ }
+ }
+ } else {
+ Ok(0)
+ }
+}
+
impl<'a> VbiosIterator<'a> {
fn new(dev: &'a device::Device, bar0: &'a Bar0) -> Result<Self> {
Ok(Self {
dev,
bar0,
data: KVec::new(),
- current_offset: 0,
+ current_offset: vbios_rom_offset(dev, bar0)?,
last_found: false,
})
}
--
2.53.0