Re: DMA transfer is not working if highmem is enabled

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Hi,



 Request you to check if the memory allocation is done using GFP_DMA
in kmalloc ???

Thanks
Sekhar

2010/10/20 Trübenbach, Ralf <Ralf.Truebenbach@xxxxxx>:
> Hello,
>
> I have a problem with our VME driver (sources see below) and high
> memory. I would like to transfer the content of a user space alloced
> buffer to another VME device using DMA (see vme4l-core.c->vme4l_zc_dma()).
> The actual driver version uses page_address() and virt_to_bus() to get
> the bus addresses needed to fill the DMA scatter list. Unfortunately
> this is not working with highmem.
>
> I tried with page_to_phys() instead of page_address/virt_to_bus which
> seems to work. But is this correct for all architectures? As far as I
> understood I have to use the bus addresses and not the physical
> addresses to fill the DMA scatter list.
>
> Maybe someone knows an example where I can have a look at, or any other
> suggestions?
>
> Thank you,
>
> Ralf
>
>
> Sources:
> --------
> http://codeviewer.org/view/code:12ed  vme4l-core.c
> http://codeviewer.org/view/code:12ee  vme4l-tsi148.c
> http://codeviewer.org/view/code:12ef  vme4l-tsi148.h
> http://codeviewer.org/view/code:12f0  vme4l-menpldz002.c
> http://codeviewer.org/view/code:12f1  vme4l-core.h
> or (complete):
> http://www.men.de/download/free/13z014-90/13z014-90_02_11.zip
>
> Best Regards/Mit freundlichen Gruessen
>
> Ralf Trübenbach
>
> ------------------------------------------------------------------------
>
> Ralf Trübenbach, Software Design
> MEN Mikro Elektronik GmbH
> Neuwieder Straße 5-7
> 90411 Nürnberg, Germany
> Phone +49-911-99 33 5-0
> Fax +49-911-99 33 5-910
> Ralf.Truebenbach@xxxxxx
> www.men.de
>
>
>
> MEN Mikro Elektronik GmbH - Manfred Schmitz (CTO), Udo Fuchs (CFO)
> - Handelsregister/Trade Register AG Nürnberg HRB 5540
>
>
>
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