After DMA redesign, the pxa_camera dynamic behaviour should
be documented so that future contributors understand how it
works, and improve it.
Signed-off-by: Robert Jarzmik <robert.jarzmik@xxxxxxx>
---
Documentation/video4linux/pxa_camera.txt | 49 ++++++++++++++++++++++++++++++
1 files changed, 49 insertions(+), 0 deletions(-)
diff --git a/Documentation/video4linux/pxa_camera.txt b/Documentation/video4linux/pxa_camera.txt
index b1137f9..b595e94 100644
--- a/Documentation/video4linux/pxa_camera.txt
+++ b/Documentation/video4linux/pxa_camera.txt
@@ -26,6 +26,55 @@ Global video workflow
Once the last buffer is filled in, the QCI interface stops.
+ c) Capture global finite state machine schema
+
+ +----+ +---+ +----+
+ | DQ | | Q | | DQ |
+ | v | v | v
+ +-----------+ +------------------------+
+ | STOP | | Wait for capture start |
+ +-----------+ Q +------------------------+
++-> | QCI: stop | ------------------> | QCI: run | <------------+
+| | DMA: stop | | DMA: stop | |
+| +-----------+ +-----> +------------------------+ |
+| / | |
+| / +---+ +----+ | |
+|capture list empty / | Q | | DQ | | QCI Irq EOF |
+| / | v | v v |
+| +--------------------+ +----------------------+ |
+| | DMA hotlink missed | | Capture running | |
+| +--------------------+ +----------------------+ |
+| | QCI: run | +-----> | QCI: run | <-+ |
+| | DMA: stop | / | DMA: run | | |
+| +--------------------+ / +----------------------+ | Other |
+| ^ /DMA still | | channels |
+| | capture list / running | DMA Irq End | not |
+| | not empty / | | finished |
+| | / v | yet |
+| +----------------------+ +----------------------+ | |
+| | Videobuf released | | Channel completed | | |
+| +----------------------+ +----------------------+ | |
+| | QCI: run | | QCI: run | --+ |
+| | DMA: run | | DMA: run | |
+| +----------------------+ +----------------------+ |
+| ^ / | |
+| | no overrun / | overrun |
+| | / v |
+| +--------------------+ / +----------------------+ |
+| | Frame completed | / | Frame overran | |
+| +--------------------+ <-----+ +----------------------+ restart frame |
++-- | QCI: run | | QCI: stop | --------------+
+ | DMA: run | | DMA: stop |
+ +--------------------+ +----------------------+
+
+ Legend: - each box is a FSM state
+ - each arrow is the condition to transition to another state
+ - an arrow with a comment is a mandatory transition (no condition)
+ - arrow "Q" means : a buffer was enqueued
+ - arrow "DQ" means : a buffer was dequeued
+ - "QCI: stop" means the QCI interface is not enabled
+ - "DMA: stop" means all 3 DMA channels are stopped
+ - "DMA: run" means at least 1 DMA channel is still running
DMA usage
---------
--
1.6.2.1
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