| Max Filippov | 93e294a | 2013-03-04 23:48:14 +0400 | [diff] [blame] | 1 | MMUv3 initialization sequence. |
| 2 | |
| 3 | The code in the initialize_mmu macro sets up MMUv3 memory mapping |
| 4 | identically to MMUv2 fixed memory mapping. Depending on |
| 5 | CONFIG_INITIALIZE_XTENSA_MMU_INSIDE_VMLINUX symbol this code is |
| 6 | located in one of the following address ranges: |
| 7 | |
| 8 | 0xF0000000..0xFFFFFFFF (will keep same address in MMU v2 layout; |
| 9 | typically ROM) |
| 10 | 0x00000000..0x07FFFFFF (system RAM; this code is actually linked |
| 11 | at 0xD0000000..0xD7FFFFFF [cached] |
| 12 | or 0xD8000000..0xDFFFFFFF [uncached]; |
| 13 | in any case, initially runs elsewhere |
| 14 | than linked, so have to be careful) |
| 15 | |
| 16 | The code has the following assumptions: |
| 17 | This code fragment is run only on an MMU v3. |
| 18 | TLBs are in their reset state. |
| 19 | ITLBCFG and DTLBCFG are zero (reset state). |
| 20 | RASID is 0x04030201 (reset state). |
| 21 | PS.RING is zero (reset state). |
| 22 | LITBASE is zero (reset state, PC-relative literals); required to be PIC. |
| 23 | |
| 24 | TLB setup proceeds along the following steps. |
| 25 | |
| 26 | Legend: |
| 27 | VA = virtual address (two upper nibbles of it); |
| 28 | PA = physical address (two upper nibbles of it); |
| 29 | pc = physical range that contains this code; |
| 30 | |
| 31 | After step 2, we jump to virtual address in 0x40000000..0x5fffffff |
| 32 | that corresponds to next instruction to execute in this code. |
| 33 | After step 4, we jump to intended (linked) address of this code. |
| 34 | |
| 35 | Step 0 Step1 Step 2 Step3 Step 4 Step5 |
| 36 | ============ ===== ============ ===== ============ ===== |
| 37 | VA PA PA VA PA PA VA PA PA |
| 38 | ------ -- -- ------ -- -- ------ -- -- |
| 39 | E0..FF -> E0 -> E0 E0..FF -> E0 F0..FF -> F0 -> F0 |
| 40 | C0..DF -> C0 -> C0 C0..DF -> C0 E0..EF -> F0 -> F0 |
| 41 | A0..BF -> A0 -> A0 A0..BF -> A0 D8..DF -> 00 -> 00 |
| 42 | 80..9F -> 80 -> 80 80..9F -> 80 D0..D7 -> 00 -> 00 |
| 43 | 60..7F -> 60 -> 60 60..7F -> 60 |
| 44 | 40..5F -> 40 40..5F -> pc -> pc 40..5F -> pc |
| 45 | 20..3F -> 20 -> 20 20..3F -> 20 |
| 46 | 00..1F -> 00 -> 00 00..1F -> 00 |