Re: use of alloc_bootmem for a PCI-e device

[Jean-Francois Dagenais <jeff.dagenais@gmail.com>]

On Nov 23, 2011, at 14:31, Michal Nazarewicz wrote:

> On Wed, 23 Nov 2011 20:30:30 +0100, Jean-Francois Dagenais <jeff.dagenais@gmail.com> wrote:
>> I am maintaining a kernel for an embedded product. We have an FPGA
>> acquisition device interfaced through PCI-e on different intel platforms.
>> The acquisition device needs an extra large physically contiguous memory
>> area to autonomously dump acquired data into.
> 
> [...]
> 
>> We are doing another incarnation of the product on an Atom E6xx which has
>> no such IOMMU and am looking into ways of allocating a huge chunk of ram.
>> Kind of like integrated gfx chips do with RAM, but I don't have the assistance
>> of the BIOS.
> 
> One trick that you might try to use (even though it's a bit hackish) is to
> pass ram=### on Linux command line where the number passed is actual memory
> minus size of the buffer you need.  Other then that, you might take a look
> at CMA (CMAv17 it was sent last week or so to linux-mm) which in one of the
> initialisation steps needs to grab memory regions.
Thanks for that, I am looking into it.

Looks like it can do what I want. Are there any mainline merge plans?

Unless I am mistaken, because of SWIOTLB, only x86_32 is supported, correct?

Since I want to allocate the buffer once at startup, then keep it until shutdown,
can you suggest a simpler, less flexible alternative? (other than the boot args
method which I consider a fallback plan).

> 
> -- 
> Best regards,                                         _     _
> .o. | Liege of Serenely Enlightened Majesty of      o' \,=./ `o
> ..o | Computer Science,  Michał “mina86” Nazarewicz    (o o)
> ooo +----<email/xmpp: mpn@google.com>--------------ooO--(_)--Ooo--
Thanks for helping!
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