Memory mapping plan
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The document discusses physical to DRAM address mapping. It shows the default mapping which creates unused memory holes for video data. An alternative mapping is proposed to reclaim these holes by using a continuous linear address space. This requires configuring the MIPS MMU to allow virtual addresses to access the alternative physical mapping rather than only the default.
![Physical Address to DRAM Address
Mapping
2048 (16 pages)
64 KB aligned 1920 (15 pages)
Bank 4m Bank 4m+1 (m = 0 or 1) Bank 4m+2 Bank 4m+3 Unused Portion
1/16 for 1920*1080
System Adr System Adr System Adr System Adr
(decimal) (decimal) (decimal) (decimal) 6/16 for 1280*720
Row Adr n
0~127 128~256 1792~1919 1920~2047 19/64 for 720*480
2048~2175 2176~2303 3840~3967 3968~4095
| | | |
| | No bank | | Dual 2KB page size
63488~63615 63616~63743 conflict 65280~65407 65408~65535 DRAM (4KB total)
Line 0~31 case for
Bank 4m + 2 Bank 4m + 3 rectangular Bank 4m Bank 4m + 1 CA[4:0] = HA[6:2]
DRAM CA[9:5] = HA[15:11]
System Adr System Adr System Adr System Adr
(hex) (hex)
access (hex) (hex)
BA[0] = HA[7]
10000~1007f 10080~100ff 10700~1077f 10780~107ff BA[1] = HA[8]^HA[16]
Row Adr n+4 10800~1087f 10880~108ff 10f00~10f7f 10f80~10fff RA[1:0] = HA[10:9]
| | | | RA[12:2] =HA[26 :16]
| | | |
Line 32~63 1f800~1f87f 1f880~1f8ff 1ff00~1ff7f 1ff80~1ffff](https://image.slidesharecdn.com/memorymappingplan-121109121357-phpapp02/85/Memory-mapping-plan-1-320.jpg)
![Alternative Mapping to Reclaim Memory Holes
2048 (16 pages)
64 KB aligned 1920 (15 pages)
Bank 4m Bank 4m+1 (m = 0 or 1) Bank 4m+2 Bank 4m+3 Continuous
address
System Adr System Adr System Adr
System Adr
Row Adr n (hex)
(hex) (hex) (hex)
100000~ e00000~ f00000~
0~fff
100fff e00fff f00fff
Dual 2KB page size
DRAM (4KB total)
Bank 4m + 2 Bank 4m + 3 Bank 4m Bank 4m + 1 CA[9:0] = HA[11:2]
BA[0] = HA[20]
System Adr
BA[1] =
System Adr
System Adr
(hex)
System Adr HA[21]^HA[12]
Row Adr n+4 (hex)
(hex)
e01000~
(hex) RA[1:0] = HA[23:22]
101000~ f01000~
1000~1fff
101fff
e01fff
f01fff RA[9:2] =HA[19:12]
RA[12:10] = HA[26:24]
System Adr
(hex)
fff000~
ffffff](https://image.slidesharecdn.com/memorymappingplan-121109121357-phpapp02/85/Memory-mapping-plan-4-320.jpg)
![MIPS Virtual to Physical Address Mapping
Virtual Address Physical Address
FFFFFFFF FFFFFFFF Same Repetitive
Kernal Mapped kseg3 DRAM Mapping
E0000000 (A[30:29] ignored)
DFFFFFFF
Supervisor Mapped kseg2
C0000000 Alternative DRAM
BFFFFFFF Kernal Unmapped Mapping
kseg1
Uncached Same Repetitive
A0000000 DRAM Mapping
9FFFFFFF
Kernal Unmapped kseg0 (A[30:29] ignored)
80000000
80000000
7FFFFFFF
7FFFFFFF
Default DRAM
User Mapped useg/kuseg Mapping
The upper 96MB
DRAM space
20000000
SPI_Flash/Device 1A000000 overlapped with
96MB
512MB SPI/Device can be
accessed here
00000000 00000000](https://image.slidesharecdn.com/memorymappingplan-121109121357-phpapp02/85/Memory-mapping-plan-6-320.jpg)
Memory mapping plan
- 1. Physical Address to DRAM Address Mapping 2048 (16 pages) 64 KB aligned 1920 (15 pages) Bank 4m Bank 4m+1 (m = 0 or 1) Bank 4m+2 Bank 4m+3 Unused Portion 1/16 for 1920*1080 System Adr System Adr System Adr System Adr (decimal) (decimal) (decimal) (decimal) 6/16 for 1280*720 Row Adr n 0~127 128~256 1792~1919 1920~2047 19/64 for 720*480 2048~2175 2176~2303 3840~3967 3968~4095 | | | | | | No bank | | Dual 2KB page size 63488~63615 63616~63743 conflict 65280~65407 65408~65535 DRAM (4KB total) Line 0~31 case for Bank 4m + 2 Bank 4m + 3 rectangular Bank 4m Bank 4m + 1 CA[4:0] = HA[6:2] DRAM CA[9:5] = HA[15:11] System Adr System Adr System Adr System Adr (hex) (hex) access (hex) (hex) BA[0] = HA[7] 10000~1007f 10080~100ff 10700~1077f 10780~107ff BA[1] = HA[8]^HA[16] Row Adr n+4 10800~1087f 10880~108ff 10f00~10f7f 10f80~10fff RA[1:0] = HA[10:9] | | | | RA[12:2] =HA[26 :16] | | | | Line 32~63 1f800~1f87f 1f880~1f8ff 1ff00~1ff7f 1ff80~1ffff
- 2. Memory Holes for Video (Boda7503) Data 1920*1080 1280*720 640*480 0000000 Video Data Video Data 1000000 2000000 Memory hole with 3000000 discontinuous address 4000000 5000000 6000000 7000000
- 3. Pros/Cons for the Address Mapping Advantage Simple DRAM memory address mapping All engines and processors see straight forward linear address layout Disadvantage Create unused scattered holes in system memory for video (Boda7503 generated) data The unused holes are difficult for software to utilize
- 4. Alternative Mapping to Reclaim Memory Holes 2048 (16 pages) 64 KB aligned 1920 (15 pages) Bank 4m Bank 4m+1 (m = 0 or 1) Bank 4m+2 Bank 4m+3 Continuous address System Adr System Adr System Adr System Adr Row Adr n (hex) (hex) (hex) (hex) 100000~ e00000~ f00000~ 0~fff 100fff e00fff f00fff Dual 2KB page size DRAM (4KB total) Bank 4m + 2 Bank 4m + 3 Bank 4m Bank 4m + 1 CA[9:0] = HA[11:2] BA[0] = HA[20] System Adr BA[1] = System Adr System Adr (hex) System Adr HA[21]^HA[12] Row Adr n+4 (hex) (hex) e01000~ (hex) RA[1:0] = HA[23:22] 101000~ f01000~ 1000~1fff 101fff e01fff f01fff RA[9:2] =HA[19:12] RA[12:10] = HA[26:24] System Adr (hex) fff000~ ffffff
- 5. Alternative Mapping to Reclaim Memory Holes Default Address Space Address Space of Extra Mapping 00000000 80000000 01000000 Same Video Data 81000000 With different address 02000000 82000000 03000000 83000000 04000000 84000000 05000000 Memory hole with 85000000 discontinuous address 06000000 86000000 07000000 Memory hole with 87000000 continuous address
- 6. MIPS Virtual to Physical Address Mapping Virtual Address Physical Address FFFFFFFF FFFFFFFF Same Repetitive Kernal Mapped kseg3 DRAM Mapping E0000000 (A[30:29] ignored) DFFFFFFF Supervisor Mapped kseg2 C0000000 Alternative DRAM BFFFFFFF Kernal Unmapped Mapping kseg1 Uncached Same Repetitive A0000000 DRAM Mapping 9FFFFFFF Kernal Unmapped kseg0 (A[30:29] ignored) 80000000 80000000 7FFFFFFF 7FFFFFFF Default DRAM User Mapped useg/kuseg Mapping The upper 96MB DRAM space 20000000 SPI_Flash/Device 1A000000 overlapped with 96MB 512MB SPI/Device can be accessed here 00000000 00000000
- 7. MIPS Virtual to Physical Address Mapping Kseg1/kseg0 cannot access alternate DRAM mapping region For 512MB DRAM, 96MB is wasted if software use only kseg1/kseg0 Software must configure MMU for kseg3/kseg2/useg to access alternative DRAM mapping space or the 96MB DRAM space that conflicts with SPI_Flash/Device space on kseg1/kseg0.