SPRUJ28E November 2021 – September 2024 AM68 , AM68A , TDA4AL-Q1 , TDA4VE-Q1 , TDA4VL-Q1
Through the WBINV_CTRL memory-mapped-register MSMC provides control for software to trigger a coherent invalidation of MSMC’s external and/or internal SRAM snoop filter(s). If a ‘1’ is written to the EMIF_SF_WBINV field in the register, then MSMC will invalidate the external snoop filter, writing back any dirty data to EMIF. If a ‘1’ is written to the SRAM_SFINV field in the register, then MSMC will invalidate the internal SRAM snoop filter and write back any dirty data into its own SRAM. If both fields are written to simultaneously, then MSMC will invalidate the external snoop filter before invalidating the internal SRAM snoop filter immediately afterwards. As part of the write back invalidation procedure, MSMC will request all coherent masters to invalidate any lines that MSMC is tracking. The behavior tree is shown in the figure below.
When the write back invalidation of the external and/or internal SRAM SF is triggered theWBINV_ACTIVE field of the WBINV_CTRL memory mapped register will be set to ‘1’ until all invalidations are complete at which time it will be reset to ‘0’. Due to shared hardware betweensnoop filter invalidation and cache resizing for looping though all of the snoop filter entries, any write to EMIF_SF_WBINV, SRAM_SF_WBINV, or the CACHE_SIZE field within the CACHE_CTRL memory mapped register will be ignored if the WBINV_ACTIVE bit is ‘1’. Similarly, writes to EMIF_SF_WBINV and SRAM_SF_WBINV are ignored if a cache resize is in progress.
MSMC will maintain coherency for any transactions that arrive during a write back invalidation procedure, although the snoop filter state for any addresses they access is not ensured to be invalid until the operation is complete. The snoop filter state for any address accessed during the invalidation of the associated snoop filter is dependent on whether or not the access occurs before or after MSMC has performed its write back invalidation on that particular snoop filter entry.