Read RPMC Parameters

RPMC Support Using eSPI OOB (eRPMC)

Architecture Specification

ID	Date	Version	Classification
739180	03/01/2023		Public

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This command is used to read RPMC parameters values.

RPMC Parameter table is as defined below:

Bits	Description
31:8	Reserved
7:4	Document Version. Default=0.
3:0	Num_RPMC: Number of supported RPMC Devices (Note)

RPMC Parameters, RPMC Device n:

Bits	Description
31:28	Update_Rate: Rate of update = 5(2*Update_Rate) seconds
27:26	RPMC Device
25	MC_Size: 0= Monotonic counter size is 32 bits, 1=Reserved. Default =0.
24	SHA_Size: 0=SHA-256, 1=SHA-384. Default =0.
23:16	Reserved
15:8	OP1: OP1 Opcode for RPMC Devices. Default= 9Bh
7:0	Num_Counter-1: Number of supported Monotonic Counters-1 (Note)

If RPMC is supported in FW in the EC device only, reports one device and number of supported counters. Num_RPMC is zero if RPMC is not supported in EC device.
If RPMC is supported by EC device and/or the EC device passing commands to SPI RPMC devices, reports the number of flash devices supported and the number of monotonic counters in each RPMC device.

Read RPMC Parameters Command:

Byte #	7	6		5		4	3	2		1	0
0	eSPI Cycle Type: OOB Message=21h
1	Tag[3:0]=0h						Length[11:8]=0h
2	Length[7:0]=0Bh
3	Dest Slave Addr[7:1]=07h										0
4	Command Code=0Fh
5	Byte Count=08h
6	Source Slave Address[7:1]= 08h										1
7	MCTP Reserved=0h						Header Version
8	Destination Endpoint ID
9	Source Endpoint ID
10	SOM		EOM		Packet Seq #		TO		Message Tag
11	IC		Message Type=7Dh
12	RPMC Device= 00h
13	Opcode = 9Fh

Response:

Byte #	7	6		5		4	3		2		1	0
0	eSPI Cycle Type: OOB Message=21h
1	Tag[3:0]=0h						Length[11:8]=0h
2	Length[7:0]=12h
3	Dest Slave Addr[7:1]=08h											0
4	Command Code=0Fh
5	Byte Count=0Fh
6	Source Slave Address[7:1]= 07h											1
7	MCTP Reserved=0h							Header Version
8	Destination Endpoint ID
9	Source Endpoint ID
10	SOM		EOM		Packet Seq #			TO		Message Tag
11	IC		Message Type=7Dh
12	Extended Status[7:0]
13	RPMC Parameter Table[31:24]
…	…
16	RPMC Parameter Table[7:0]
17	RPMC Parameters, RPMC Device 0[31:24]
…	…
20	RPMC Parameters, RPMC Device 0[7:0]

Note:This command may return up to three additional DWs, depending on number of RPMC Devices.

If the received transaction has errors, the device does not execute the transaction and posts the corresponding error in extended status.

Expected Extended Status [7:0] results:

Extended Status [7:0]	Description
10000000	Successful completion.
0XXXXXX1	N/A. This bit cannot be read as 1, eRPMC not supported.
0XXXXX1X	This bit is only set when incorrect payload size is received.

Examples of RPMC Devices Supported

The following show examples of different RPMC devices (EC, SPI flash devices or both). Parameter table values and relevant MCTP command parameters for each example are shown.

EC is RPMC Device

RPMC Parameter Table:

Bits	Description	Value
31:8	Reserved	000000h
7:4	Document Version. Default=0.	0h
3:2	Reserved	00b
1:0	Num_RPMC: Number of supported RPMC Devices	01b

RPMC Parameters, RPMC Device 0:

Bits	Description	Value
31:28	Update_Rate	0h
27:26	RPMC Device	00b
25	MC_Size	0b
24	SHA_Size: 0=SHA-256, 1=SHA-384. Default =0.	0b
23:16	Reserved	00h
15:8	OP1: OP1 Opcode for RPMC Devices. Default= 9Bh	9Bh
7:0	Num_Counter-1: Number of supported Monotonic Counters-1	0-FFh

RPMC OOB Command Parameters, RPMC Device 0:

Parameter	Value
RPMC Device	00h
Counter Addr[7:0]	00h-FFh

Two RPMC SPI Flash Devices, Each with Four Monotonic Counters

RPMC Parameter Table:

Bits	Description	Value
31:8	Reserved	000000h
7:4	Document Version. Default=0.	0h
3:2	Reserved	00b
1:0	Num_RPMC: Number of supported RPMC Devices	02b

RPMC Parameters, RPMC Device 0:

Bits	Description	Value
31:28	Update_Rate	0h
27:26	RPMC Device	00b
25	MC_Size	0b
24	SHA_Size: 0=SHA-256, 1=SHA-384. Default =0.	0b
23:16	Reserved	00h
15:8	OP1: OP1 Opcode for RPMC Devices. Default= 9Bh	9Bh
7:0	Num_Counter-1: Number of supported Monotonic Counters-1	03h

RPMC OOB Command Parameters, RPMC Device 0:

Parameter	Value
RPMC Device	00h
Counter Addr[7:0]	00h-03h

RPMC Parameters, RPMC Device 1:

Bits	Description	Value
31:28	Update_Rate	0h
27:26	RPMC Device	01b
25	MC_Size	0b
24	SHA_Size: 0=SHA-256, 1=SHA-384. Default =0.	0b
23:16	Reserved	00h
15:8	OP1: OP1 Opcode for RPMC Devices. Default= 9Bh	9Bh
7:0	Num_Counter-1: Number of supported Monotonic Counters-1	03h

RPMC OOB Command Parameters, RPMC Device 1:

Parameter	Value
RPMC Device	01h
Counter Addr[7:0]	00h-03h

EC as RPMC Device and Two SPI RPMC Flash Devices

RPMC Parameter Table:

Bits	Description	Value
31:8	Reserved	000000h
7:4	Document Version. Default=0.	0h
3:2	Reserved	00b
1:0	Num_RPMC: Number of supported RPMC Devices	03b

RPMC Parameters, RPMC Device 0 (EC):

Bits	Description	Value
31:28	Update_Rate	0h
27:26	RPMC Device	00b
25	MC_Size	0b
24	SHA_Size: 0=SHA-256, 1=SHA-384. Default =0.	0b
23:16	Reserved	00h
15:8	OP1: OP1 Opcode for RPMC Devices. Default= 9Bh	9Bh
7:0	Num_Counter-1: Number of supported Monotonic Counters-1	FFh

RPMC OOB Command Parameters, RPMC Device 0 (EC):

Parameter	Value
RPMC Device	00h
Counter Addr[7:0]	00h-FFh

RPMC Parameters, RPMC Device 1:

Bits	Description	Value
31:28	Update_Rate	0h
27:26	RPMC Device	01b
25	MC_Size	0b
24	SHA_Size: 0=SHA-256, 1=SHA-384. Default =0.	0b
23:16	Reserved	00h
15:8	OP1: OP1 Opcode for RPMC Devices. Default= 9Bh	9Bh
7:0	Num_Counter-1: Number of supported Monotonic Counters-1	03h

RPMC OOB Command Parameters, RPMC Device 1:

Parameter	Value
RPMC Device	01h
Counter Addr[7:0]	00h-03h

RPMC Parameters, RPMC Device 2:

Bits	Description	Value
31:28	Update_Rate	0h
27:26	RPMC Device	02b
25	MC_Size	0b
24	SHA_Size: 0=SHA-256, 1=SHA-384. Default =0.	0b
23:16	Reserved	00h
15:8	OP1: OP1 Opcode for RPMC Devices. Default= 9Bh	9Bh
7:0	Num_Counter-1: Number of supported Monotonic Counters-1	03h

RPMC OOB Command Parameters, RPMC Device 2:

Parameter	Value
RPMC Device	02h
Counter Addr[7:0]	00h-03h