On Friday, August 13, 2010 10:13:08 pm Janusz Krzysztofik wrote: > Friday 13 August 2010 11:11:52 Marin Mitov napisał(a): > > On Friday, August 13, 2010 11:52:41 am Guennadi Liakhovetski wrote: > > > On Fri, 13 Aug 2010, Janusz Krzysztofik wrote: > > > > Thursday 12 August 2010 23:38:17 Guennadi Liakhovetski napisał(a): > > > > > 1. We've discussed this dynamic switching a bit on IRC today. The > > > > > first reaction was - you probably should concentrate on getting the > > > > > contiguous version to work reliably. I.e., to reserve the memory in > > > > > the board init code similar, how other contig users currently do it. > > > > > > > > I already tried before to find out how I could allocate memory at init > > > > without reinventing a new videobuf-dma-contig implementation. Since in > > > > the Documentation/video4linux/videobuf I've read that videobuf does not > > > > currently play well with drivers that play tricks by allocating DMA > > > > space at system boot time, I've implemented the alternate sg path. > > > > > > > > If it's not quite true what the documentation says and you can give me > > > > a hint how this could be done, I might try again. > > > > > > For an example look at > > > arch/arm/mach-mx3/mach-pcm037.c::pcm037_camera_alloc_dma(). > > Yes, this is the solution that suffers from the already discussed limitation > of not being able to remap a memory with different attributes, which affects > OMAP1 as well. > > > For preallocating dma-coherent memory for device personal use during device > > probe() time (when the memory is less fragmented compared to open() time) > > see also dt3155_alloc_coherent/dt3155_free_coherent in > > drivers/staging/dt3155v4l/dt3155vfl.c (for x86 arch, I do not know if it > > works for arm arch) > > With this workaround applied, I get much better results, thank you Marin. > However, it seems not bullet proof, since mmap still happens to fail for a > reason not quite clear to me: > This is just a preallocation of coherent memory kept for further private driver use, should not be connected to mmap problem. > > Maybe I should preallocate a few more pages than will be actually used by the > driver? > > Anyways, I'm not sure if this piece of code could be accepted for inclusion > into the mainline tree, perhaps only under drivers/staging. The idea for the piece of code I have proposed to you is taken from the functions dma_declare_coherent_memory()/dma_release_declared_memory() in mainline drivers/base/dma-coherent.c > > Thanks, > Janusz > -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
