On Mon, May 11, 2020 at 04:45:02PM +0300, Serge Semin wrote: > On Mon, May 11, 2020 at 12:58:13PM +0100, Mark Brown wrote: > > That sounds like you need to also impose a limit on the maximum message > > size as well then, with that you should be able to handle messages up > > to whatever that limit is. There's code for that bit already, so long > > as the limit is not too low it should be fine for most devices and > > client drivers can see the limit so they can be updated to work with it > > if needed. > Hmm, this might work. The problem will be with imposing such limitation through > the DW APB SSI driver. In order to do this I need to know: > 1) Whether multi-block LLP is supported by the DW DMA controller. > 2) Maximum DW DMA transfer block size. There is a constraint enumeration interface in the DMA API which you should be able to extend for this if it doesn't already support what you need. > Then I'll be able to use this information in the can_dma() callback to enable > the DMA xfers only for the safe transfers. Did you mean something like this when > you said "There's code for that bit already" ? If you meant the max_dma_len > parameter, then setting it won't work, because it just limits the SG items size > not the total length of a single transfer. You can set max_transfer_size and/or max_message_size in the SPI driver - you should be able to do this on probe.
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