| We Have Atomic Operation Control (ATOMCTL) Register. |
| This register determines the effect of using a S32C1I instruction |
| with various combinations of: |
| |
| 1. With and without an Coherent Cache Controller which |
| can do Atomic Transactions to the memory internally. |
| |
| 2. With and without An Intelligent Memory Controller which |
| can do Atomic Transactions itself. |
| |
| The Core comes up with a default value of for the three types of cache ops: |
| |
| 0x28: (WB: Internal, WT: Internal, BY:Exception) |
| |
| On the FPGA Cards we typically simulate an Intelligent Memory controller |
| which can implement RCW transactions. For FPGA cards with an External |
| Memory controller we let it to the atomic operations internally while |
| doing a Cached (WB) transaction and use the Memory RCW for un-cached |
| operations. |
| |
| For systems without an coherent cache controller, non-MX, we always |
| use the memory controllers RCW, thought non-MX controlers likely |
| support the Internal Operation. |
| |
| CUSTOMER-WARNING: |
| Virtually all customers buy their memory controllers from vendors that |
| don't support atomic RCW memory transactions and will likely want to |
| configure this register to not use RCW. |
| |
| Developers might find using RCW in Bypass mode convenient when testing |
| with the cache being bypassed; for example studying cache alias problems. |
| |
| See Section 4.3.12.4 of ISA; Bits: |
| |
| WB WT BY |
| 5 4 | 3 2 | 1 0 |
| 2 Bit |
| Field |
| Values WB - Write Back WT - Write Thru BY - Bypass |
| --------- --------------- ----------------- ---------------- |
| 0 Exception Exception Exception |
| 1 RCW Transaction RCW Transaction RCW Transaction |
| 2 Internal Operation Internal Operation Reserved |
| 3 Reserved Reserved Reserved |
