LPDDR4x SPD tools README

Tools for generating SPD files for LPDDR4x memory used in memory down configurations on Intel Tiger Lake (TGL) and Jasper Lake (JSL) based platforms. These tools generate SPDs following JESD209-4C specification and Intel recommendations (doc #616599, #610202) for LPDDR4x SPD.

There are two tools provided that assist TGL and JSL based mainboards to generate SPDs and Makefile to integrate these SPDs in coreboot build. These tools can also be used to allocate DRAM IDs (configure DRAM hardware straps) for any LPDDR4x memory part used by the board.

• gen_spd.go: Generates de-duplicated SPD files using a global memory part list provided by the mainboard in JSON format. Additionally, generates a SPD manifest file(in CSV format) with information about what memory part from the global list uses which of the generated SPD files.

• gen_part_id.go: Allocates DRAM strap IDs for different LPDDR4x memory parts used by the board. Takes as input list of memory parts used by the board (with one memory part on each line) and the SPD manifest file generated by gen_spd.go. Generates Makefile.inc for integrating the generated SPD files in the coreboot build.

Tool 1 - gen_spd.go

This program takes as input:

• Pointer to directory where the generated SPD files and manifest will be placed.
• JSON file containing a global list of memory parts with their attributes as per the datasheet. This is the list of all known LPDDR4x memory parts irrespective of their usage on the board.
• SoC platform name for which the SPDs are being generated. Currently supported platform names are TGL and JSL.

Input JSON file requires the following two fields for every memory part:

• name: Name of the memory part
• attribs: List of attributes of the memory part as per its datasheet. These attributes match the part specifications and are independent of any SoC expectations. Tool takes care of translating the physical attributes of the memory part to match JEDEC and Intel MRC expectations.

attribs field further contains two types of sub-fields:

• Mandatory: These attributes have to be provided for a memory part.
• Optional: These attributes can be provided by memory part if it wants to override the defaults.

Mandatory attribs

• densityPerChannelGb: Density in Gb of the physical channel.

• banks: Number of banks per physical channel. This is typically 8 for LPDDR4x memory parts.

• channelsPerDie: Number of physical channels per die. Valid values: 1, 2, 4. For a part with x16 bit width, number of channels per die is 1 or 2. For a part with x8 bit width, number of channels can be 2 or 4 (4 is basically when two dual-channel byte mode devices are combined as shown in Figure 3 in JESD209-4C).

• diesPerPackage: Number of physical dies in each SDRAM package. As per JESD209-4C, “Standard LPDDR4 package ballmaps allocate one ZQ ball per die.” Thus, number of diesPerPackage is the number of ZQ balls on the package.

• bitWidthPerChannel: Width of each physical channel. Valid values: 8, 16 bits.

• ranksPerChannel: Number of ranks per physical channel. Valid values: 1, 2. If the channels across multiple dies share the same DQ/DQS pins but use a separate CS, then ranks is 2 else it is 1.

• speedMbps: Maximum data rate supported by the part in Mbps. Valid values: 3200, 3733, 4267 Mbps.

Optional attribs

• trfcabNs: Minimum Refresh Recovery Delay Time (tRFCab) for all banks in nanoseconds. As per JESD209-4C, this is dependent on the density per channel. Default values used:

  • 6Gb : 280ns
  • 8Gb : 280ns
  • 12Gb: 380ns
  • 16Gb: 380ns

• trfcpbNs: Minimum Refresh Recovery Delay Time (tRFCab) per bank in nanoseconds. As per JESD209-4C, this is dependent on the density per channel. Default values used:

  • 6Gb : 140ns
  • 8Gb : 140ns
  • 12Gb: 190ns
  • 16Gb: 190ns

• trpabMinNs: Minimum Row Precharge Delay Time (tRPab) for all banks in nanoseconds. As per JESD209-4C, this is max(21ns, 4nck) which defaults to 21ns.

• trppbMinNs: Minimum Row Precharge Delay Time (tRPpb) per bank in nanoseconds. As per JESD209-4C, this is max(18ns, 4nck) which defaults to 18ns.

• tckMinPs: SDRAM minimum cycle time (tckMin) value in picoseconds. This is typically calculated based on the speedMbps attribute. (1 / speedMbps) * 2. Default values used(taken from JESD209-4C):

  • 4267 Mbps: 468ps
  • 3733 Mbps: 535ps
  • 3200 Mbps: 625ps

• tckMaxPs: SDRAM maximum cycle time (tckMax) value in picoseconds. Default value used: 31875ps. As per JESD209-4C, TCKmax should be 100ns (100000ps) for all speed grades. But the SPD byte to encode this field is only 1 byte. Hence, the maximum value that can be encoded is 31875ps.

• taaMinPs: Minimum CAS Latency Time(taaMin) in picoseconds. This value defaults to nck * tckMin, where nck is minimum CAS latency.

• trcdMinNs: Minimum RAS# to CAS# Delay Time (tRCDmin) in nanoseconds. As per JESD209-4C, this is max(18ns, 4nck) which defaults to 18ns.

• casLatencies: List of CAS latencies supported by the part. This is dependent on the attrib speedMbps. Default values used:

  • 4267: "6 10 14 20 24 28 32 36".
  • 3733: "6 10 14 20 24 28 32".
  • 3200: "6 10 14 20 24 28".

Example JSON file

{
    "parts": [
        {
            "name": "MEMORY_PART_A",
            "attribs": {
                "densityPerChannelGb": 8,
                "banks": 8,
                "channelsPerDie": 2,
                "diesPerPackage": 2,
                "bitWidthPerChannel": 16,
                "ranksPerChannel": 1,
                "speedMbps": 4267
            }
        },
        {
            "name": "MEMORY_PART_B",
            "attribs": {
                "densityPerChannelGb": 8,
                "banks": 8,
                "channelsPerDie": 1,
                "diesPerPackage": 2,
                "bitWidthPerChannel": 16,
                "ranksPerChannel": 1,
                "speedMbps": 3733,
                "casLatencies": "14 20 24 28 32",
                "tckMaxPs": "1250"
            }
        }
    ]
}

Output

This tool generates the following files using the global list of memory parts in JSON format as described above:

• De-duplicated SPDs required for the different memory parts. These SPD files are named (spd_1.hex, spd_2.hex, spd_3.hex and so on) and placed in the directory provided as an input to the tool.
• CSV file representing which of the deduplicated SPD files is used by which memory part. This file is named as spd_manifest.generated.txt and placed in the directory provided as an input to the tool along with the generated SPD files. Example CSV file:

  MEMORY_PART_A, spd_1.hex
  MEMORY_PART_B, spd_2.hex
  MEMORY_PART_C, spd_3.hex
  MEMORY_PART_D, spd_2.hex
  MEMORY_PART_E, spd_2.hex
  

Tool 2 - gen_part_id.go

This program takes as input:

• Pointer to directory where the SPD files and the manifest file spd_manifest.generated.txt (in CSV format) are placed by gen_spd.go
• File containing list of memory parts used by the board. Each line of the file is supposed to contain one memory part name as present in the global list of memory parts provided to gen_spd.go
• Pointer to directory where the generated Makefile.inc should be placed by the tool.

Output

This program provides the following:

• Prints out the list of DRAM hardware strap IDs that should be allocated to each memory part listed in the input file.
• Makefile.inc is generated in the provided directory to integrate SPDs generated by gen_spd.go with the coreboot build for the board.
• dram_id.generated.txt is generated in the same directory as Makefile. This contains the part IDs assigned to the different memory parts. (Useful to integrate in board schematics).

Sample output (dram_id.generated.txt):

DRAM Part Name                 ID to assign
MEMORY_PART_A                  0 (0000)
MEMORY_PART_B                  1 (0001)
MEMORY_PART_C                  2 (0010)
MEMORY_PART_D                  1 (0001)

Sample Makefile.inc:

## SPDX-License-Identifier: GPL-2.0-or-later
## This is an auto-generated file. Do not edit!!

SPD_SOURCES =
SPD_SOURCES += spd_1.hex      # ID = 0(0b0000)  Parts = MEMORY_PART_A
SPD_SOURCES += spd_2.hex      # ID = 1(0b0001)  Parts = MEMORY_PART_B, MEMORY_PART_D
SPD_SOURCES += spd_3.hex      # ID = 2(0b0010)  Parts = MEMORY_PART_C

Note of caution

This program assigns DRAM IDs using the order of DRAM part names provided in the input file. Thus, when adding a new memory part to the list, it should always go to the end of the input text file. This guarantees that the memory parts that were already assigned IDs do not change.

How to build the tools?

# go build gen_spd.go
# go build gen_part_id.go

How to use the tools?

# ./gen_spd <spd_dir> <mem_parts_list_json> <platform>
# ./gen_part_id <spd_dir> <makefile_dir> <mem_parts_used_file>

Need to add a new memory part for a board?

• If the memory part is not present in the global list of memory parts, then add the memory part name and attributes as per the datasheet to the file containing the global list.
  • Use gen_spd.go with input as the file containing the global list of memory parts to generate de-duplicated SPDs.
  • If a new SPD file is generated, use git add to add it to the tree and push a CL for review.
• Update the file containing memory parts used by board (variant) to add the new memory part name at the end of the file.
  • Use gen_part_id.go providing it pointer to the location where SPD files are stored and file containing the list of memory parts used by the board(variant).
  • Use git add to add Makefile.inc and dram_id.generated.txt with updated changes and push a CL for review.