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From:   Jeremy Linton <jeremy.linton@arm.com>
Subject: [BUG] XHCI getting ZONE_DMA32 memory > than its bus_dma_limit
Message-ID: <34619bdf-6527-ae82-7e4d-e2ea7c67ed56@arm.com>
Date:   Thu, 2 Jul 2020 12:49:14 -0500
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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,