Hi,
my processor is MPC8247, on Linux 2.6.11
in MPC8247 manual reference, the interrupt of DMA unit belonged PCI bridge.
that is different from SDMA and IDMA. through i do not know what 's the
different. heard SDMA is used to transfer between CPM and 60x. DMA is used
to transfer between 60x bus and PCI, or 60x bus - 60x bus. i am not sure.
Whether or not you get packing bytes when you access a
16-bit device and transfer the data to a 32-bit destination
depends on how the device is mapped. For example, a 16-bit
device can be implemented such that it responds to 8-bit,
16-bit, and 32-bit requests, but the 32-bit requests will
require more wait-states, since the device has to be
read from twice before constructing a 32-bit word to
place on the PCI bus.
ya, that's it
Its also possible that the DMA controller can be configured
to deal with different source and destination widths. However
without knowing what processor or DMA controller you are
asking about, theres not much to say.
in the manual reference charpter 9.13 DMA, source and destination address
can be configured. i can not find the hint about source and destination
widths configured.
I won't have a chance to look at the MPC8247 manual, so
I'll just give a general comment.
If you are DMAing from an internal peripheral, then it's
width will be hard-coded and can be read from the user-manual.
If you are DMAing from a local bus then the local bus definition
should determine what happens. For example, on the MPC8349, you
can put 16-bit flash on the local bus, and configure the local
bus controller to know that it is 16-bits wide. A 32-bit access
by the CPU or DMA controller will generate two reads on the
local bus.
You can investigate to see whether the MPC8247 works similarly.
Cheers,
Dave
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