From 817c8f0bb112747f2a53670b1bfb85489a9399a7 Mon Sep 17 00:00:00 2001 From: Miquel Raynal Date: Thu, 23 Jan 2025 23:24:42 +0100 Subject: [PATCH] kernel: dma: Soften the dma_map_resources() interest It is not clear who should remap the MMIO resources when using an external DMA engine. Signed-off-by: Miquel Raynal --- .../kernel-driver-development-dma.tex | 6 +++--- 1 file changed, 3 insertions(+), 3 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 fc1c63a1a6..876bb3128e 100644 --- a/slides/kernel-driver-development-dma/kernel-driver-development-dma.tex +++ b/slides/kernel-driver-development-dma/kernel-driver-development-dma.tex @@ -258,8 +258,8 @@ \subsection{Kernel APIs for DMA} \begin{frame}[fragile] \frametitle{\code{dma-mapping}: Setting up streaming I/O mappings} - Physical addresses with MMIO registers shall always be remapped - (otherwise it would not work when they are accessed through an IO-MMU) + Physical addresses with MMIO registers might need to be remapped in order to + be accessed through an IO-MMU: \vfill \begin{minted}[fontsize=\scriptsize]{c} #include @@ -312,7 +312,7 @@ \subsection{Kernel APIs for DMA} \item The CPU shall only access the buffer after unmapping! \item If however the same memory region has to be used for several DMA transfers, the same mapping can be kept in place. In this case the - data must be synchronized before CPU access: + data must be synchronized before access: \begin{itemize} \item The CPU needs to access the data: \begin{minted}[fontsize=\small]{c}