Messages in this thread | | | Subject | Re: [PATCH net] macmace: Set platform device coherent_dma_mask | From | Michael Schmitz <> | Date | Fri, 4 May 2018 20:16:58 +1200 |
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Hi Geert,
Am 04.05.2018 um 19:24 schrieb Geert Uytterhoeven: > Hi Michael, > >>> Yes, that would be useful. The other assumption could be that >>> platform devices always allow an all-0xff dma mask. >> >> That's not always true (Atari NCR5380 SCSI and floppy would use a 24 >> bit DMA mask). We use bounce buffers allocated from a dedicated lowmem >> pool there currently, and for all I know don't use the DMA API yet. >> >> I bet that is a rare exception though. Setting the default DMA mask >> for platform devices to all-0xff and letting the few odd drivers force >> a different setting seems the best way forward. > > I'd say that's usually a property of the platform, not of the device?
Right - I was thinking 'm68k' as platform, not a particular machine like Mac or Falcon (the 24 bit mask only applies to that particular model anyway).
> So IMHO it belongs in the platform code, not in the device driver code.
OK - let's have a default mask of 64 bit, and allow machine specific platform_init() to override using a new helper function.
Cheers,
Michael
> Gr{oetje,eeting}s, > > Geert >
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