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+This document describes the cx2341x memory map and documents some of the register
+space.
+
+Warning! This information was figured out from searching through the memory and
+registers, this information may not be correct and is certainly not complete, and
+was not derived from anything more than searching through the memory space with
+commands like:
+
+        ivtvctl -O min=0x02000000,max=0x020000ff
+
+So take this as is, I'm always searching for more stuff, it's a large
+register space :-).
+
+Memory Map
+==========
+
+The cx2341x exposes its entire 64M memory space to the PCI host via the PCI BAR0
+(Base Address Register 0). The addresses here are offsets relative to the
+address held in BAR0.
+
+0x00000000-0x00ffffff Encoder memory space
+0x00000000-0x0003ffff Encode.rom
+      ???-???         MPEG buffer(s)
+      ???-???         Raw video capture buffer(s)
+      ???-???         Raw audio capture buffer(s)
+      ???-???         Display buffers (6 or 9)
+
+0x01000000-0x01ffffff Decoder memory space
+0x01000000-0x0103ffff Decode.rom
+      ???-???         MPEG buffers(s)
+0x0114b000-0x0115afff Audio.rom (deprecated?)
+
+0x02000000-0x0200ffff Register Space
+
+Registers
+=========
+
+The registers occupy the 64k space starting at the 0x02000000 offset from BAR0.
+All of these registers are 32 bits wide.
+
+DMA Registers 0x000-0xff:
+
+ 0x00 - Control:
+        0=reset/cancel, 1=read, 2=write, 4=stop
+ 0x04 - DMA status:
+        1=read busy, 2=write busy, 4=read error, 8=write error, 16=link list error
+ 0x08 - pci DMA pointer for read link list
+ 0x0c - pci DMA pointer for write link list
+ 0x10 - read/write DMA enable:
+        1=read enable, 2=write enable
+ 0x14 - always 0xffffffff, if set any lower instability occurs, 0x00 crashes
+ 0x18 - ??
+ 0x1c - always 0x20 or 32, smaller values slow down DMA transactions
+ 0x20 - always value of 0x780a010a
+ 0x24-0x3c - usually just random values???
+ 0x40 - Interrupt status
+ 0x44 - Write a bit here and shows up in Interrupt status 0x40
+ 0x48 - Interrupt Mask
+ 0x4C - always value of 0xfffdffff,
+        if changed to 0xffffffff DMA write interrupts break.
+ 0x50 - always 0xffffffff
+ 0x54 - always 0xffffffff (0x4c, 0x50, 0x54 seem like interrupt masks, are
+        3 processors on chip, Java ones, VPU, SPU, APU, maybe these are the
+        interrupt masks???).
+ 0x60-0x7C - random values
+ 0x80 - first write linked list reg, for Encoder Memory addr
+ 0x84 - first write linked list reg, for pci memory addr
+ 0x88 - first write linked list reg, for length of buffer in memory addr
+        (|0x80000000 or this for last link)
+ 0x8c-0xcc - rest of write linked list reg, 8 sets of 3 total, DMA goes here
+        from linked list addr in reg 0x0c, firmware must push through or
+        something.
+ 0xe0 - first (and only) read linked list reg, for pci memory addr
+ 0xe4 - first (and only) read linked list reg, for Decoder memory addr
+ 0xe8 - first (and only) read linked list reg, for length of buffer
+ 0xec-0xff - Nothing seems to be in these registers, 0xec-f4 are 0x00000000.
+
+Memory locations for Encoder Buffers 0x700-0x7ff:
+
+These registers show offsets of memory locations pertaining to each
+buffer area used for encoding, have to shift them by <<1 first.
+
+0x07F8: Encoder SDRAM refresh
+0x07FC: Encoder SDRAM pre-charge
+
+Memory locations for Decoder Buffers 0x800-0x8ff:
+
+These registers show offsets of memory locations pertaining to each
+buffer area used for decoding, have to shift them by <<1 first.
+
+0x08F8: Decoder SDRAM refresh
+0x08FC: Decoder SDRAM pre-charge
+
+Other memory locations:
+
+0x2800: Video Display Module control
+0x2D00: AO (audio output?) control
+0x2D24: Bytes Flushed
+0x7000: LSB I2C write clock bit (inverted)
+0x7004: LSB I2C write data bit (inverted)
+0x7008: LSB I2C read clock bit
+0x700c: LSB I2C read data bit
+0x9008: GPIO get input state
+0x900c: GPIO set output state
+0x9020: GPIO direction (Bit7 (GPIO 0..7) - 0:input, 1:output)
+0x9050: SPU control
+0x9054: Reset HW blocks
+0x9058: VPU control
+0xA018: Bit6: interrupt pending?
+0xA064: APU command
+
+
+Interrupt Status Register
+=========================
+
+The definition of the bits in the interrupt status register 0x0040, and the
+interrupt mask 0x0048. If a bit is cleared in the mask, then we want our ISR to
+execute.
+
+Bit
+31 Encoder Start Capture
+30 Encoder EOS
+29 Encoder VBI capture
+28 Encoder Video Input Module reset event
+27 Encoder DMA complete
+26
+25 Decoder copy protect detection event
+24 Decoder audio mode change detection event
+23
+22 Decoder data request
+21 Decoder I-Frame? done
+20 Decoder DMA complete
+19 Decoder VBI re-insertion
+18 Decoder DMA err (linked-list bad)
+
+Missing
+Encoder API call completed
+Decoder API call completed
+Encoder API post(?)
+Decoder API post(?)
+Decoder VTRACE event