Hi Tomasz, On Friday 12 Aug 2016 16:31:47 Tomasz Figa wrote: > On Tue, Aug 9, 2016 at 7:49 AM, Sricharan R wrote: > > From: Laurent Pinchart <laurent.pinchart+rene...@ideasonboard.com> > > > > The of_configure_dma() function configures both the DMA masks and ops. > > Moving DMA ops configuration to probe time would thus also delay > > configuration of the DMA masks, which might not be safe. To avoid issues > > Do we know any example cases when it might be unsafe? I think we kind > of rely on the fact that DMA mapping (and so DMA masks as well) is not > used before probing the device anyway, because we let the IOMMU > attachment happen at probe time, which essentially makes any earlier > attempts to use DMA mapping on such device incorrect.
I don't know of any such situation, but (if I remember correctly) when I discussed the IOMMU rework with Arnd Bergman and Will Deacon there was a concern that someone, somewhere was relying on the mask being set early. I personally would like to drop this patch, but it might be difficult to ensure this wouldn't cause a regression. There should certainly be no DMA mapping created before IOMMU attachment, but the DMA mask could possibly be used somewhere else. -- Regards, Laurent Pinchart _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu
