BD allocation and IDMA driver question

BD allocation and IDMA driver question

[kas turi]

Hi
 I would like to know what is the difference between
m8260_cpm_hostalloc and m8260_dp_alloc. The FCC driver
uses the former API and the serial driver uses the
latter API. When I try to use m8260_cpm_hostalloc to
allocate buffer descriptor for the SPI driver the
timesys 2.4 kernel hangs. When I use m8260_dp_alloc
the SPI driver works.
  Has anybody developed a IDMA driver for 8260 for 2.4
kernel?
  Thanks in advance.


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Re: BD allocation and IDMA driver question

[Dan Malek]

kas turi wrote:

>  I would like to know what is the difference between
> m8260_cpm_hostalloc and m8260_dp_alloc.

The 'hostalloc' allocates from a small pool of host memory.
This is usually used for small FIFOs as there is only a
page or so for use by the entire system.  The 'dp_alloc'
allocates from the CPM dual ported memory.

> .... The FCC driver
> uses the former API and the serial driver uses the
> latter API.

If you would read the comment in the FCC driver, you may
understand why :-)

> ..... When I try to use m8260_cpm_hostalloc to
> allocate buffer descriptor for the SPI driver the
> timesys 2.4 kernel hangs. When I use m8260_dp_alloc
> the SPI driver works.

The 'hostalloc' returns a kernel virtual address.  You
have to convert this to a physical address for the CPM DMA.

>   Has anybody developed a IDMA driver for 8260 for 2.4
> kernel?

There have been discussions about it on this mailing list.
You may wish to search the archives for more information.


	-- Dan


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