MPAMCFG_CMAX, MPAM Cache Maximum Capacity Partition Configuration Register

The MPAMCFG_CMAX characteristics are:

Purpose

The MPAMCFG_CMAX is a 32-bit read/write register that controls the maximum fraction of the cache capacity that the PARTID selected by MPAMCFG_PART_SEL is permitted to allocate.

MPAMCFG_CMAX_s controls the cache maximum capacity for the Secure PARTID selected by the Secure instance of MPAMCFG_PART_SEL. MPAMCFG_CMAX_ns controls the cache maximum capacity for the Non-secure PARTID selected by the Non-secure instance of MPAMCFG_PART_SEL. MPAMCFG_CMAX_rt controls the cache maximum capacity for the Root PARTID selected by the Root instance of MPAMCFG_PART_SEL. MPAMCFG_CMAX_rl controls the cache maximum capacity for the Realm PARTID selected by the Realm instance of MPAMCFG_PART_SEL.

If MPAMF_IDR.HAS_RIS is 1, the control settings accessed are those of the resource instance currently selected by MPAMCFG_PART_SEL.RIS and the PARTID selected by MPAMCFG_PART_SEL.PARTID_SEL.

Configuration

The power domain of MPAMCFG_CMAX is IMPLEMENTATION DEFINED.

This register is present only when FEAT_MPAM is implemented, MPAMF_IDR.HAS_CCAP_PART == 1 and MPAMF_CCAP_IDR.NO_CMAX == 0. Otherwise, direct accesses to MPAMCFG_CMAX are RES0.

The power and reset domain of each MSC component is specific to that component.

Attributes

MPAMCFG_CMAX is a 32-bit register.

Field descriptions

31	30	29	28	27	26	25	24	23	22	21	20	19	18	17	16	15	14	13	12	11	10	9	8	7	6	5	4	3	2	1	0
SOFTLIM	RES0															CMAX

SOFTLIM, bit [31]
When (FEAT_MPAMv0p1 is implemented or FEAT_MPAMv1p1 is implemented) and MPAMF_CCAP_IDR.HAS_CMAX_SOFTLIM == 1:

Soft limiting of CMAX. Soft limiting allows some allocations by a PARTID when its cache use is above the CMAX maximum cache capacity.

SOFTLIM	Meaning
0b0	When CMAX cache capacity is exceeded, the partition is not allowed to increase its cache capacity usage. It is only permitted to replace a line that was previously occupied by a line allocated by that PARTID.
0b1	When CMAX cache capacity is exceeded, the partition is permitted to allocate capacity beyond CMAX, but only from invalid lines or lines belonging to disabled PARTIDs.

Otherwise:

Reserved, RES0.

Bits [30:16]

Reserved, RES0.

CMAX, bits [15:0]

Maximum cache capacity usage in fixed-point fraction format by the partition selected by MPAMCFG_PART_SEL. The fraction represents the portion of the total cache capacity that the PARTID is permitted to allocate.

The implemented width of the fixed-point fraction is given in MPAMF_CCAP_IDR.CMAX_WD. Unimplemented bits within the field are RAZ/WI. The implemented bits of the CMAX field are always the most significant bits of the field.

The fixed-point fraction CMAX is less than 1. The implied binary point is between bits 15 and 16. In an implementation with w implemented bits, the largest fraction of the cache that can be represented is 1- (0.5)^w.

Accessing MPAMCFG_CMAX

This register is within the MPAM feature page memory frames.

In a system that supports Secure, Non-secure, Root, and Realm memory maps, there must be MPAM feature pages in all four address maps:

MPAMCFG_CMAX_s must only be accessible from the Secure MPAM feature page.
MPAMCFG_CMAX_ns must only be accessible from the Non-secure MPAM feature page.
MPAMCFG_CMAX_rt must only be accessible from the Root MPAM feature page.
MPAMCFG_CMAX_rl must only be accessible from the Realm MPAM feature page.

MPAMCFG_CMAX_s, MPAMCFG_CMAX_ns, MPAMCFG_CMAX_rt, and MPAMCFG_CMAX_rl must be separate registers:

The Secure instance (MPAMCFG_CMAX_s) accesses the cache capacity partitioning used for Secure PARTIDs.
The Non-secure instance (MPAMCFG_CMAX_ns) accesses the cache capacity partitioning used for Non-secure PARTIDs.
The Root instance (MPAMCFG_CMAX_rt) accesses the cache capacity partitioning used for Root PARTIDs.
The Realm instance (MPAMCFG_CMAX_rl) accesses the cache capacity partitioning used for Realm PARTIDs.

When RIS is implemented, loads and stores to MPAMCFG_CMAX access the cache maximum capacity partitioning configuration settings for the cache resource instance selected by MPAMCFG_PART_SEL.RIS and the PARTID selected by MPAMCFG_PART_SEL.PARTID_SEL.

When RIS is not implemented, loads and stores to MPAMCFG_CMAX access the cache maximum capacity partitioning configuration settings for the PARTID selected by MPAMCFG_PART_SEL.PARTID_SEL.

When PARTID narrowing is implemented, loads and stores to MPAMCFG_CMAX access the cache maximum capacity partitioning configuration settings for the internal PARTID selected by MPAMCFG_PART_SEL.PARTID_SEL, and MPAMCFG_PART_SEL.INTERNAL must be 1.

When PARTID narrowing is not implemented, loads and stores to MPAMCFG_CMAX access the cache maximum capacity partitioning configuration settings for the request PARTID selected by MPAMCFG_PART_SEL.PARTID_SEL, and MPAMCFG_PART_SEL.INTERNAL must be 0.

MPAMCFG_CMAX can be accessed through the memory-mapped interfaces:

Component	Frame	Offset	Instance
MPAM	MPAMF_BASE_s	0x0108	MPAMCFG_CMAX_s

Accesses on this interface are RW.

Component	Frame	Offset	Instance
MPAM	MPAMF_BASE_ns	0x0108	MPAMCFG_CMAX_ns