On Sun, 2019-11-10 at 15:36 +1300, Michael Schmitz wrote: > All of the old board-specific drivers used a max transfer length of > 0x1000000, only the fastlane driver used 0xfffc. That lower limit > might be due to a DMA limitation on the fastlane board. We could > accommodate the different limit for this board by using a board- > specific dma_length_limit() callback... Sure, that implies the minimum dma burst length is 4 bytes ... > > case for any of the cards the zorro_esp drives, it might be better > > to lower the max length to 61440 (64k-4k) so the residual is a > > page. > > For the benefit of keeping the code simple, and avoid retesting the > fastlane board, that might indeed be the better solution. ... which means you don't have to lower the limit by 4k as I suggested, because I was being incredibly conservative about what the dma burst length might be, just use 0xfffc as the default. I think raising to 0x1000000 for boards which can support it is fine too if you want to add the extra logic to the driver. James
