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Doc/nb/intel/haswell: Drop outdated section about SPD addresses

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The docs talk about left-shifting SPD addresses by 1. This was necessary
back when mainboard code would directly set the values of the members in
`struct pei_data`, which stopped being the case with commit 1e2821882f
("nb/intel/haswell: Use unshifted SPD addresses in mainboards").

Given that `util/autoport` (which now supports Haswell / Lynx Point) has
documentation on how to figure out the SPD address mapping in a platform
agnostic format, drop the outdated section from Haswell-specific docs.

Change-Id: I3d118b2e116cf2cd0096c8ef27e2fd22e6e548ae
Signed-off-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/91759
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Matt DeVillier <matt.devillier@gmail.com>
This commit is contained in:
Angel Pons 2026-03-19 09:19:48 +01:00 • committed by Matt DeVillier
commit 5e146277ae
1 changed files with 0 additions and 77 deletions
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77
Documentation/northbridge/intel/haswell/mrc.bin.md
View file

@ -27,83 +27,6 @@ Now, place `mrc.bin` in the root of the coreboot directory.
Alternatively, place `mrc.bin` anywhere you want, and set `MRC_FILE` to
its location when building coreboot.
## SPD Addresses
When porting a board from vendor firmware, the SPD addresses can be obtained
through `i2c-tools`, which can be found in many GNU/Linux distributions. A more
[detailed description](https://hannuhartikainen.fi/blog/hacking-ddr3-spd/) of
the procedure and beyond can be found in
[Hannu Hartikainen's blog](https://hannuhartikainen.fi).
First load the kernel modules:
```bash
modprobe i2c-dev
modprobe eeprom
```
Find the SMBus and the addresses of the DIMM's EEPROMs (example output):
```bash
$ decode-dimms | grep Decoding
Decoding EEPROM: /sys/bus/i2c/drivers/eeprom/7-0050
Decoding EEPROM: /sys/bus/i2c/drivers/eeprom/7-0052
```
Alternatively, look at the sys filesystem:
```bash
$ ls -l /sys/bus/i2c/drivers/eeprom/
total 0
lrwxrwxrwx 1 root root 0 Apr 4 01:46 6-0050 -> ../../../../devices/pci0000:00/0000:00:02.0/drm/card0/card0-eDP-1/i2c-6/6-0050/
lrwxrwxrwx 1 root root 0 Apr 4 01:46 7-0050 -> ../../../../devices/pci0000:00/0000:00:1f.3/i2c-7/7-0050/
lrwxrwxrwx 1 root root 0 Apr 4 01:46 7-0052 -> ../../../../devices/pci0000:00/0000:00:1f.3/i2c-7/7-0052/
--w------- 1 root root 4096 Apr 4 01:47 bind
lrwxrwxrwx 1 root root 0 Apr 4 01:47 module -> ../../../../module/eeprom/
--w------- 1 root root 4096 Apr 4 01:46 uevent
--w------- 1 root root 4096 Apr 4 01:47 unbind
```
The correct I2C bus is 7 in this case, and the EEPROMs are at `0x50` and `0x52`.
Note that the above values are actually hex values.
You can check the correctness of the SMBus and the addresses of the EEPROMs via
`i2cdetect`:
```bash
$ i2cdetect -l
i2c-3 unknown i915 gmbus dpc N/A
i2c-1 unknown i915 gmbus vga N/A
i2c-6 unknown DPDDC-A N/A
i2c-4 unknown i915 gmbus dpb N/A
i2c-2 unknown i915 gmbus panel N/A
i2c-0 unknown i915 gmbus ssc N/A
i2c-7 unknown SMBus I801 adapter at f040 N/A
i2c-5 unknown i915 gmbus dpd N/A
```
Probing the SMBus:
```bash
$ i2cdetect -r 7
WARNING! This program can confuse your I2C bus, cause data loss and worse!
I will probe file /dev/i2c-7 using receive byte commands.
I will probe address range 0x03-0x77.
Continue? [Y/n]
0 1 2 3 4 5 6 7 8 9 a b c d e f
00: -- -- -- -- -- -- -- -- -- -- -- -- --
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
30: 30 -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
40: -- -- -- -- 44 -- -- -- -- -- -- -- -- -- -- --
50: UU -- UU -- -- -- -- -- -- -- -- -- -- -- -- --
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
70: -- -- -- -- -- -- -- --
```
The SPD addresses need to be left-shifted by 1 for `mrc.bin`, i.e., multiplied
by 2. For example, if the addresses read through `i2c-tools` when booted from
vendor firmware are `0x50` and `0x52`, the correct values would be `0xa0` and
`0xa4`. This is because the I2C addresses are 7 bits long.
## ECC DRAM
When `mrc.bin` has finished executing, ECC is active on the channels