[BUG] XHCI getting ZONE_DMA32 memory > than its bus_dma_limit

[Jeremy Linton]

Hi,

Using 5.8rc3:

The rpi4 has a 3G dev->bus_dma_limit on its XHCI controller. With a usb3 
hub, plus a few devices plugged in, randomly devices will fail 
operations. This appears to because xhci_alloc_container_ctx() is 
getting buffers > 3G via dma_pool_zalloc().

Tracking that down, it seems to be caused by dma_alloc_from_pool() using 
dev_to_pool()->dma_direct_optimal_gfp_mask() to "optimistically" select 
the atomic_pool_dma32 but then failing to verify that the allocations in 
the pool are less than the dev bus_dma_limit.

Thanks,