Merge tag 'dma-mapping-4.19' of git://git.infradead.org/users/hch/dma-mapping

Pull dma-mapping updates from Christoph Hellwig:

 - a series from Robin to fix bus imposed dma limits by adding a
   separate mask for them to struct device instead of trying to squeeze
   a second meaning out of the existing dma mask as we did before.

   This has ACKs from the various other subsystems touched

 - a small swiotlb cleanup from Kees (acked by Konrad)

 - conversion of nios2 and sh to the new generic dma-noncoherent code.

   Various other architecture conversions will come through the
   architectures maintainers trees.

* tag 'dma-mapping-4.19' of git://git.infradead.org/users/hch/dma-mapping:
  sh: use generic dma_noncoherent_ops
  sh: split arch/sh/mm/consistent.c
  sh: use dma_direct_ops for the CONFIG_DMA_COHERENT case
  sh: introduce a sh_cacheop_vaddr helper
  sh: simplify get_arch_dma_ops
  OF: Don't set default coherent DMA mask
  ACPI/IORT: Don't set default coherent DMA mask
  iommu/dma: Respect bus DMA limit for IOVAs
  of/device: Set bus DMA mask as appropriate
  ACPI/IORT: Set bus DMA mask as appropriate
  dma-mapping: Generalise dma_32bit_limit flag
  ACPI/IORT: Support address size limit for root complexes
  of/platform: Initialise default DMA masks
  nios2: use generic dma_noncoherent_ops
  swiotlb: clean up reporting
  dma-mapping: relax warning for per-device areas

1 files changed, 8 insertions, 1 deletions

diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
index f9cc309507d9..1db6a6b46d0d 100644
--- a/include/linux/dma-mapping.h
+++ b/include/linux/dma-mapping.h
@@ -538,10 +538,17 @@ static inline void dma_free_attrs(struct device *dev, size_t size,
 	const struct dma_map_ops *ops = get_dma_ops(dev);
 
 	BUG_ON(!ops);
-	WARN_ON(irqs_disabled());
 
 	if (dma_release_from_dev_coherent(dev, get_order(size), cpu_addr))
 		return;
+	/*
+	 * On non-coherent platforms which implement DMA-coherent buffers via
+	 * non-cacheable remaps, ops->free() may call vunmap(). Thus getting
+	 * this far in IRQ context is a) at risk of a BUG_ON() or trying to
+	 * sleep on some machines, and b) an indication that the driver is
+	 * probably misusing the coherent API anyway.
+	 */
+	WARN_ON(irqs_disabled());
 
 	if (!ops->free || !cpu_addr)
 		return;