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-rw-r--r--Documentation/soc/intel/broadwell/blobs.md19
1 files changed, 19 insertions, 0 deletions
diff --git a/Documentation/soc/intel/broadwell/blobs.md b/Documentation/soc/intel/broadwell/blobs.md
index b9f99afe667f..01ce7c9827c3 100644
--- a/Documentation/soc/intel/broadwell/blobs.md
+++ b/Documentation/soc/intel/broadwell/blobs.md
@@ -29,6 +29,25 @@ field. For boards with an Intel GbE device, a modification of `refcode` is neede
otherwise `refcode` will disable the Intel GbE device and the OS cannot find it
in the list of PCI devices.
+For the refcode binary extracted from Purism Librem 13 v1 (SHA256:
+8a919ffece61ba21664b1028b0ebbfabcd727d90c1ae2f72b48152b8774323a4,
+.program section starts at file offset 0x2040), we can see the
+following code sequence:
+
+ 1e06b: c6 43 0c 00 movb $0x0,0xc(%ebx)
+ 1e06f: c6 83 7e 03 00 00 00 movb $0x0,0x37e(%ebx)
+ 1e076: c6 83 70 03 00 00 01 movb $0x1,0x370(%ebx)
+ 1e07d: 66 89 43 0a mov %ax,0xa(%ebx)
+ 1e081: c6 83 da 01 00 00 01 movb $0x1,0x1da(%ebx)
+ 1e088: c6 83 86 03 00 00 01 movb $0x1,0x386(%ebx)
+
+The code at 0x1e06f sets the field that is to enable the GbE to the
+hardcoded 0 value. Change the byte at 0x1e075 (file offset 0x200b5)
+to 0x01 to make the refcode support Intel GbE:
+
+ cp refcode.elf refcode_gbe.elf
+ printf '\x01' | dd of=refcode_gbe.elf bs=1 seek=131253 count=1 conv=notrunc
+
## Use Broadwell SoC code for Haswell ULT boards
Haswell ULT boards can use Broadwell SoC code. To use Broadwell code for Haswell ULT