Re: [PATCH v2] dmaengine: mpc512x: fix dead empty check in mpc_dma_prep_slave_sg()

[Maoyi Xie]

Thanks all. I'm dropping this one. Using list_first_entry_or_null activates
the recovery path, and calling mpc_dma_process_completed() from prep context
isn't safe. It runs client callbacks inline and can roll completed_cookie
backwards. The empty free list is real but rare (all 64 descriptors in
flight). The safe fix is to return NULL there without that call and let the
tasklet reclaim, but I can't test it on hardware, so I'll leave it to you.

Best,
Maoyi