Messages in this thread | | | From | Geert Uytterhoeven <> | Date | Mon, 7 Nov 2016 19:57:11 +0100 | Subject | Re: [PATCH 2/2] swiotlb: Add swiotlb=nobounce debug option |
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Hi Konrad,
On Mon, Oct 31, 2016 at 6:52 PM, Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> wrote: > On Mon, Oct 31, 2016 at 04:45:04PM +0100, Geert Uytterhoeven wrote: >> On architectures like arm64, swiotlb is tied intimately to the core >> architecture DMA support. In addition, ZONE_DMA cannot be disabled. >> >> To aid debugging and catch devices not supporting DMA to memory outside >> the 32-bit address space, add a kernel command line option >> "swiotlb=nobounce", which disables the use of bounce buffers. >> If specified, trying to map memory that cannot be used with DMA will >> fail, and a warning will be printed (rate-limited). > > I would make the 'swiotlb_force' an enum. And then instead of this > being 'nobounce' just do the inverse of 'force', that is the > 'noforce' would trigger this no bounce effect. > > So: > > enum { > NORMAL, /* Default - depending on the hardware DMA mask and such. */ > FORCE, /* swiotlb=force */ > NO_FORCE, /* swiotlb=noforce */
Fine for me, but swiotlb_force is exported to platform code. Hence all users should be updated?
Gr{oetje,eeting}s,
Geert
-- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds
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