driver-api/dmaengine/pxa_dma.rst

2 PXA/MMP - DMA Slave controller
21 This implies that even if an irq/tasklet is triggered by end of tx1, but
22 at the time of irq/dma tx2 is already finished, tx1->complete() and
23 tx2->complete() should be called.
36 A driver should be able to request a priority, especially the real-time
46 b) Transfer anatomy for a scatter-gather transfer
50    +------------+-----+---------------+----------------+-----------------+
51    | desc-sg[0] | ... | desc-sg[last] | status updater | finisher/linker |
52    +------------+-----+---------------+----------------+-----------------+
54 This structure is pointed by dma->sg_cpu.
57     - desc-sg[i]: i-th descriptor, transferring the i-th sg
60     - status updater
66     - finisher: has ddadr=DADDR_STOP, dcmd=ENDIRQEN
68     - linker: has ddadr= desc-sg[0] of next transfer, dcmd=0
70 c) Transfers hot-chaining
76    +---------+----+---+  +----+----+----+---+
78    +---------+----+-|-+  ^----+----+----+---+
80                     +----+
87    +---------+----+---+  +----+----+----+---+  +----+----+----+---+
89    +---------+----+-|-+  ^----+----+----+-|-+  ^----+----+----+---+
91                     +----+                +----+
95 restarted. Hot-chaining doesn't break the assumption that
100 - if Buffer1 and Buffer2 had all their addresses 8 bytes aligned
102 - and if Buffer3 has at least one address not 4 bytes aligned
104 - then hot-chaining cannot happen, as the channel must be stopped, the
127 - reading the physical channel last updater mark
129 - calling all the transfer callbacks of finished transfers, based on
144  - there are not "acked" transfers (tx0)
146  - a driver submitted an aligned tx1, not chained
148  - a driver submitted an aligned tx2 => tx2 is cold chained to tx1
150  - a driver issued tx1+tx2 => channel is running in aligned mode
152  - a driver submitted an aligned tx3 => tx3 is hot-chained
154  - a driver submitted an unaligned tx4 => tx4 is put in submitted queue,
157  - a driver issued tx4 => tx4 is put in issued queue, not chained
159  - a driver submitted an aligned tx5 => tx5 is put in submitted queue, not
162  - a driver submitted an aligned tx6 => tx6 is put in submitted queue,
167  - issued queue
171       +-----+ +-----+ +-----+ +-----+
172       | tx1 | | tx2 | | tx3 | | tx4 |
173       +---|-+ ^---|-+ ^-----+ +-----+
175           +---+   +---+
176         - submitted queue
177       +-----+ +-----+
179       +---|-+ ^-----+
181           +---+
183 - completed queue : empty
185 - allocated queue : tx0