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
