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include: Update dimm_info documentation 

Reference the JEDEC SPD spec and clarify some comments.

BRANCH=dimm-info
BUG=b:65403853
TEST=Documentation change only

Signed-off-by: Raul E Rangel <rrangel@chromium.org>
Change-Id: I1f2a3a70919c34f17472904323ec5accdfc876be
Reviewed-on: https://review.coreboot.org/25301
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
This commit is contained in:
Raul E Rangel 2018-03-20 12:37:27 -06:00 committed by Aaron Durbin
parent 8cf149007f
commit 5041e9b416
1 changed files with 52 additions and 3 deletions
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55
src/include/memory_info.h
View File

@ -23,24 +23,73 @@
#define DIMM_INFO_PART_NUMBER_SIZE 19
#define DIMM_INFO_TOTAL 8 /* Maximum num of dimm is 8 */
/*
/**
* If this table is filled and put in CBMEM,
* then these info in CBMEM will be used to generate smbios type 17 table
*
* Values are specified according to the JEDEC SPD Standard.
*/
struct dimm_info {
/*
* Size of the module in MiB.
*/
uint32_t dimm_size;
/*
* SMBIOS (not SPD) device type.
*
* See the smbios.h smbios_memory_device_type enum.
*/
uint16_t ddr_type;
uint16_t ddr_frequency;
uint8_t rank_per_dimm;
uint8_t channel_num;
uint8_t dimm_num;
uint8_t bank_locator;
/* The last byte is '\0' for the end of string */
/*
* The last byte is '\0' for the end of string.
*
* Even though the SPD spec defines this field as a byte array the value
* is passed directly to SMBIOS as a string, and thus must be printable
* ASCII.
*/
uint8_t serial[DIMM_INFO_SERIAL_SIZE];
/* The last byte is '\0' for the end of string */
/*
* The last byte is '\0' for the end of string
*
* Must contain only printable ASCII.
*/
uint8_t module_part_number[DIMM_INFO_PART_NUMBER_SIZE];
/*
* SPD Manufacturer ID
*/
uint16_t mod_id;
/*
* SPD Module Type.
*
* See spd.h for valid values.
*
* e.g., SPD_RDIMM, SPD_SODIMM, SPD_MICRO_DIMM
*/
uint8_t mod_type;
/*
* SPD bus width.
*
* Bits 0 - 2 encode the primary bus width:
* 0b000 = 8 bit width
* 0b001 = 16 bit width
* 0b010 = 32 bit width
* 0b011 = 64 bit width
*
* Bits 3 - 4 encode the extension bits (ECC):
* 0b00 = 0 extension bits
* 0b01 = 8 bit of ECC
*
* e.g.,
* 64 bit bus with 8 bits of ECC (72 bits total): 0b1011
* 64 bit bus with 0 bits of ECC (64 bits total): 0b0011
*
* See the smbios.h smbios_memory_bus_width enum.
*/
uint8_t bus_width;
} __packed;