driver-api/dmaengine/pxa_dma.rst

8 a) Transfers hot queuing
9 A driver submitting a transfer and issuing it should be granted the transfer
10 is queued even on a running DMA channel.
14 A transfer which is submitted and issued on a phy doesn't wait for a phy to
15 stop and restart, but is submitted on a "running channel". The other
17 a new transfer.
20 Any issued transfer with DMA_PREP_INTERRUPT should trigger a callback call.
26 A driver should be able to query if a channel is running or not. For the
27 multimedia case, such as video capture, if a transfer is submitted and then
28 a check of the DMA channel reports a "stopped channel", the transfer should
30 know if a channel is in running or stopped state.
36 A driver should be able to request a priority, especially the real-time
41 a) Virtual channels
42 Same concept as in sa11x0 driver, ie. a driver was assigned a "virtual
46 b) Transfer anatomy for a scatter-gather transfer
61       Transfers a single u32 to a well known dma coherent memory to leave
62       a trace that this transfer is done. The "well known" is unique per
63       physical channel, meaning that a read of this value will tell which
82 After a call to dmaengine_submit(b3), the chain will look like:
105   "align bit" must be set, and the channel restarted As a consequence,
106   such a transfer tx_submit() will be queued on the submitted queue, and
110 Each time a transfer is completed on a channel, an interrupt might be
112 descriptor of a transfer, the "status updater", will write the latest
117 any lock to find out what is the latest completed transfer in a running
121 When a transfer flagged as "DMA_PREP_INTERRUPT" is finished, the dma irq
122 is raised. Upon this interrupt, a tasklet is scheduled for the physical
132 If a transfer is completed while this handling is done, a dma irq will
133 be raised, and the tasklet will be scheduled once again, having a new
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,