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GDMA CONTROLLER
S3C2501X
9-6
9.3.1.1 Problem Solving with Programmable Round-Robin
S3C2501X has stuff to thing about with GDMA arbiter. This only applies to GDMA arbiter with Round-Robin
priority. Assuming all '0's are set for GDMA programmable priority register for Round-Robin, HPRIR (all same
bus occupancy in Round-Robin), and only three of six channels of GDMA are used, the problem arises as
follows.
Number
DPRIR
Channel
Expected Bus
Occupancy
Actual GDMA
Channel Run
Real System
Bus Occupancy
1
0
GDMA 0
1/3
GDMA 0
1/6
2
0
GDMA 1
1/3
GDMA 1
1/6
3
0
GDMA 2
1/3
GDMA 2
1/6
4
0
Not used
0
GDMA 0
1/6
5
0
Not used
0
GDMA 0
1/6
6
0
Not used
0
GDMA 0
1/6
When DPRIR is 0x0 and only GDMA channel 0, 1, and 2 are used, the expected bus occupancy for each channel
is 1/3. However, S3C2501X does not work in that way, instead, GDMA channel 0 gets 4/6 of the bus occupancy,
GDMA 1 1/6, and GDMA 2 1/6. In short, GDMA 0 is run four times more than GDMA 1, and 2. This is because
S3C2501X is designed to turn the bus occupancy to the next channel when there is non-used GDMA channel. For
instance,
Number 1: GDMA 0
Number 2: GDMA 1
Number 3: GDMA 2
Number 4: No GDMA
→
go to number 5: No GDMA
→
go to number 6: No GDMA
→
go to number 1: GDMA 0
Number 5: No GDMA
→
go to number 6: No GDMA
→
go to number 1: GDMA 0
Number 6: No GDMA
→
go to number 1: GDMA 0
Summary of Contents for S3C2501X
Page 18: ......
Page 275: ...MEMORY CONTROLLER S3C2501X 5 60 NOTES ...
Page 289: ...I2C CONTROLLER S3C2501X 6 14 NOTES ...
Page 373: ...GDMA CONTROLLER S3C2501X 9 24 NOTES ...
Page 435: ...I O PORTS S3C2501X 12 12 NOTES ...