> -------- Original-Nachricht -------- > Datum: Fri, 09 Jun 2006 20:46:32 -0400 > Von: Lee Revell <rlrevell@xxxxxxxxxxx> > An: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx> > Betreff: Re: RFC: dma_mmap_coherent() for powerpc/ppc architecture and > ALSA? > > On Sat, 2006-06-10 at 10:34 +1000, Benjamin Herrenschmidt wrote: > > > This leads me to the question, if there are any plans to include the > > > dma_mmap_coherent() function (for powerpc/ppc and/or any other > > > platform) in one of the next kernel versions and if an adapation of > > > the ALSA drivers is planned. Or is there a simple way (hack) to fix > > > this problem? > > > > You are welcome to do a patch implementing this :) > > Please cc: alsa-devel when you do so. :) Well, implementing the dma_mmap_coherent() function isn't the problem, because it is already implemented for the ARM architecture. But as far as I understand this would require a rewrite of all the ALSA drivers (or at least a rewrite of the ALSA's DMA helper functions). Original mail included for alsa-devel mailing list: > I'm trying to adapt Linux for the AmigaOne, which is a G3/G4 PPC desktop > system with a non cache coherent northbridge (MAI ArticiaS), a VIA82C686B > southbridge and the U-boot firmware. Due to the cache coherency problem I > compiled in the CONFIG_NOT_COHERENT_CACHE option > (arch/ppc/kernel/dma-mapping.c) in the AmigaOne Linux kernel. > While that fixes the DMA data corruption problem, it causes a kernel oops > or a complete system lookup after starting sound playback. With kernel > versions =<2.6.14 the oops messages refered to a BUG() entry in > mm/rmap.c. Therefore I tried out a newer kernel (2.6.16.15), where the > oops refers to the ALSA function snd_pcm_mmap_data_nopage() implemented > in pcm_native.c. > Well, after searching a while in some old linux kernel threads, I found > this thread here: > http://www.thisishull.net/showthread.php?t=22080&page=3&pp=10 > Based on the information in this thread, I came to the conclusion that > ALSA simply won't work on non cache coherent architectures (except ARM), > because the generic DMA API was never expanded to support the > functionality required by ALSA (namely mapping dma pages into user space > with dma_mmap_coherent()). > This leads me to the question, if there are any plans to include the > dma_mmap_coherent() function (for powerpc/ppc and/or any other platform) > in one of the next kernel versions and if an adapation of the ALSA > drivers is planned. Or is there a simple way (hack) to fix this problem? Gerhard -- Der GMX SmartSurfer hilft bis zu 70% Ihrer Onlinekosten zu sparen! Ideal für Modem und ISDN: http://www.gmx.net/de/go/smartsurfer _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.sourceforge.net/lists/listinfo/alsa-devel
