[bootlin/training-materials updates] master: DMA slides: using commit/invalidate instead of "flushing" for caches (1991e304)

[Michael Opdenacker]

Repository : https://github.com/bootlin/training-materials
On branch  : master
Link       : https://github.com/bootlin/training-materials/commit/1991e30416c707b3c731355be04cd5854c60bbc2

>---------------------------------------------------------------

commit 1991e30416c707b3c731355be04cd5854c60bbc2
Author: Michael Opdenacker <michael.opdenacker at bootlin.com>
Date:   Thu Dec 12 11:07:29 2019 +0100

    DMA slides: using commit/invalidate instead of "flushing" for caches
    
    - That's more explicit and correct in my opinion
    
    Signed-off-by: Michael Opdenacker <michael.opdenacker at bootlin.com>


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1991e30416c707b3c731355be04cd5854c60bbc2
 .../kernel-driver-development-dma.tex                      | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/slides/kernel-driver-development-dma/kernel-driver-development-dma.tex b/slides/kernel-driver-development-dma/kernel-driver-development-dma.tex
index 68c88799..c25291a8 100644
--- a/slides/kernel-driver-development-dma/kernel-driver-development-dma.tex
+++ b/slides/kernel-driver-development-dma/kernel-driver-development-dma.tex
@@ -53,8 +53,8 @@
       the cache than the bus)
     \item But the DMA does not access the CPU cache, so one needs to
       take care of cache coherency (cache content vs. memory content)
-    \item Either flush or invalidate the cache lines corresponding to
-      the buffer accessed by DMA and processor at strategic times
+    \item Either commit or invalidate the cache lines corresponding to
+      the buffer accessed by DMA and processor at the right times
     \end{itemize}
   \end{itemize}
 \end{frame}
@@ -78,17 +78,17 @@
   \begin{itemize}
   \item Before DMA to device
     \begin{itemize}
-    \item Need to make sure that all writes to DMA buffer are
+    \item Need to make sure that all writes to the DMA buffer are
       committed.
     \end{itemize}
   \item After DMA from device
     \begin{itemize}
-    \item Before drivers read from DMA buffer, need to make sure
-      that memory caches are flushed.
+    \item Before drivers read from a DMA buffer, need to make sure
+      that the corresponding memory cache lines are invalidated.
     \end{itemize}
   \item Bidirectional DMA
     \begin{itemize}
-    \item Need to flush caches before and after the DMA transfer.
+    \item Need to do both of the above operations
     \end{itemize}
   \end{itemize}
 \end{frame}
@@ -98,7 +98,7 @@
   The kernel DMA utilities can take care of:
   \begin{itemize}
   \item Either allocating a buffer in a cache coherent area,
-  \item Or making sure caches are flushed when required,
+  \item Or making sure caches are handled when required,
   \item Managing the DMA mappings and IOMMU (if any).
   \item See \kerneldoctext{DMA-API.txt} for details about the
     Linux DMA generic API.