On Fri, Jan 31, 2020 at 05:14:01PM +0530, Kishon Vijay Abraham I wrote:
> > Can you throw in a little debug printk if this comes from
> > dma_direct_possible or swiotlb_map?
> 
> I could see swiotlb_tbl_map_single() returning DMA_MAPPING_ERROR.
> 
> Kernel with debug print:
> https://github.com/kishon/linux-wip.git nvm_dma_issue
> 
> Full log: https://pastebin.ubuntu.com/p/Xf2ngxc3kB/

Ok, this mostly like means we allocate a swiotlb buffer that isn't
actually addressable.  To verify that can you post the output with the
first attached patch?  If it shows the overflow message added there,
please try if the second patch fixes it.