When scatter-gather mode is enabled, the TMC uses tables in memory to find the addresses of pages of memory to use for trace storage.All pages are 4KB in size, and each is referenced by a single entry in the tables. The tables form a linked list, to ensure that the tables themselves not required to be larger than 4KB.
Figure 2.6 shows the format of the scatter-gather tables.
Table 2.3 shows the format of the 32-bit entries used in this table.
|[31:4]||Bits [39:12] of an address. Bits [11:0] are always zero. The meaning of this field is dependent on the entry type.|
The TMC fetches each page table entry while the previous page is being written to, so that page table reads do not impact performance. When the last entry is reached, the TMC fetches the first entry from the first page table again.