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

[Timur Tabi <ttabi@nvidia.com>]

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 | 39 +++++++++++++++++++++++++++++++++-
 1 file changed, 38 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/nova-core/vbios.rs b/drivers/gpu/nova-core/vbios.rs
index e726594eb130..a7ec68448a4a 100644
--- a/drivers/gpu/nova-core/vbios.rs
+++ b/drivers/gpu/nova-core/vbios.rs
@@ -89,13 +89,50 @@ struct VbiosIterator<'a> {
     last_found: bool,
 }
 
+/// IFR signature: ASCII "NVGI" as a little-endian u32.
+const IFR_SIGNATURE: u32 = 0x4947564E;
+/// ROM directory signature: ASCII "RFRD" as a little-endian u32.
+const ROM_DIRECTORY_SIGNATURE: u32 = 0x44524652;
+
 impl<'a> VbiosIterator<'a> {
     fn new(dev: &'a device::Device, bar0: &'a Bar0) -> Result<Self> {
+        let sig = bar0.try_read32(ROM_OFFSET)?;
+
+        let current_offset = if sig == IFR_SIGNATURE {
+            let fixed1 = bar0.try_read32(ROM_OFFSET + 4)?;
+            let version = ((fixed1 >> 8) & 0xff) as u8;
+
+            match version {
+                // Note: We do not actually expect to see v1 or v2 on these GPUs
+                1 | 2 => {
+                    let fixed_data_size = ((fixed1 >> 16) & 0x7fff) as usize;
+                    bar0.try_read32(ROM_OFFSET + fixed_data_size + 4)? as usize
+                }
+                3 => {
+                    let fixed2 = bar0.try_read32(ROM_OFFSET + 8)?;
+                    let total_data_size = (fixed2 & 0x000f_ffff) as usize;
+                    let dir_offset = bar0.try_read32(ROM_OFFSET + total_data_size)? as usize + 4096;
+                    let dir_sig = bar0.try_read32(ROM_OFFSET + dir_offset)?;
+                    if dir_sig != ROM_DIRECTORY_SIGNATURE {
+                        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", version);
+                    return Err(EINVAL);
+                }
+            }
+        } else {
+            0
+        };
+
         Ok(Self {
             dev,
             bar0,
             data: KVec::new(),
-            current_offset: 0,
+            current_offset,
             last_found: false,
         })
     }
-- 
2.53.0