ARM SMMU versions 1 and 2: Difference between revisions
| [unchecked revision] | [unchecked revision] |
Content deleted Content added
mNo edit summary |
No edit summary |
||
Line 46:
** When the SSD space is present in the SMMU, the SMMU_SSDRn registers are present.
** These SMMU_SSDRn registers are bitfields, 32 bits each. If bit<N> is 1 then device<N> is non-secure, else it is secure.
The Stream Mapping table is global and shared between Secure and non-secure mode. Secure mode must decide how many Stream Mapping register groups it will expose for non-secure mode's use. ARM recommends that secure mode software leaves at least one Stream mapping register group for use by non-secure software.
Having an SMMU_S2CR which has been allocated to secure be configured to mode point to a context bank which is non-secure is UNPREDICTABLE. Having an SMMU_S2CR which has been allocated to non-secure mode be configured to point to a context bank which is secure will trigger an Unimplemented Context Bank SMMU Fault. 'This proviso doesn't make much sense unless SMMU_CBn_* registers are mode-specific'.
=== Translation, bypass and faulting ===
Line 132 ⟶ 136:
When a client transaction comes in from upstream, if client transaction processing is enabled (SMMU_sCR0.CLIENTPD==0), the SMMU must decide what SMMU context to use to translate the transaction into the output transaction which will eventually be emitted downstream by the SMMU. The process of determining which Context bank should be used to handle client transactions sent by a particular upstream StreamID is an "associative search" [sic] which uses one of 3 methods: Stream Matching, Compressed Stream Indexing or Stream Indexing.
The Stream Mapping table is global and shared between Secure and non-secure mode. Secure mode must decide how many Stream Mapping register groups it will expose for non-secure mode's use. ARM recommends that secure mode software leaves at least one Stream mapping register group for use by non-secure software. To set the number of Stream mapping regs exposed to non-secure mode, use SMMU_SCR1.NSNUMSMRGO. The SMMU will intelligently deduce the number of SMR regs to tell non-secure mode about, and will report the appropriate number to a non-secure reader through SMMU_IDR0.NUMSMRG.
| |||