[PATCH v2 1/2] Documentation/barriers: Add memory barrier dma_mb()
From: Kefeng Wang <hidden>
Date: 2022-05-20 03:05:23
Also in:
linux-doc, lkml
Subsystem:
documentation, linux kernel memory consistency model (lkmm), the rest · Maintainers:
Jonathan Corbet, Alan Stern, Andrea Parri, Will Deacon, Peter Zijlstra, Boqun Feng, Nicholas Piggin, David Howells, Jade Alglave, Luc Maranget, "Paul E. McKenney", Linus Torvalds
The memory barrier dma_mb() is introduced by commit a76a37777f2c
("iommu/arm-smmu-v3: Ensure queue is read after updating prod pointer"),
which is used to ensure that prior (both reads and writes) accesses to
memory by a CPU are ordered w.r.t. a subsequent MMIO write.
Signed-off-by: Kefeng Wang <redacted>
---
Documentation/memory-barriers.txt | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/Documentation/memory-barriers.txt b/Documentation/memory-barriers.txt
index b12df9137e1c..1eabcc0e4eca 100644
--- a/Documentation/memory-barriers.txt
+++ b/Documentation/memory-barriers.txt@@ -1894,10 +1894,13 @@ There are some more advanced barrier functions: (*) dma_wmb(); (*) dma_rmb(); + (*) dma_mb(); These are for use with consistent memory to guarantee the ordering of writes or reads of shared memory accessible to both the CPU and a - DMA capable device. + DMA capable device, in the case of ensure the prior (both reads and + writes) accesses to memory by a CPU are ordered w.r.t. a subsequent + MMIO write, dma_mb(). For example, consider a device driver that shares memory with a device and uses a descriptor status value to indicate if the descriptor belongs
--
2.35.3
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