Documentation/core-api/dma-isa-lpc.rst

12 ------------------------
16 	#include <linux/dma-mapping.h>
20 bus addresses (see Documentation/core-api/dma-api.rst for details).
28 -----------------
37 The DMA-able address space is the lowest 16 MB of _physical_ memory.
39 or 128 KiB depending on which channel you use).
45 allocate the memory during boot-up it's a good idea to also pass
52 -------------------
54 To translate the virtual address to a bus address, use the normal DMA
55 API. Do _not_ use isa_virt_to_bus() even though it does the same
66 --------
69 8-bit transfers and the upper four are for 16-bit transfers.
72 channel 4 is used to give DMA access for the second controller (0-3).
73 This means that of the four 16-bits channels only three are usable.)
80 The ability to use 16-bit or 8-bit transfers is _not_ up to you as a
85 -------------
89 Before you use any ISA DMA routines you need to claim the DMA lock
94 The first time you use the DMA controller you should call
96 controller that is used for the non-atomic operations. As long as you
105 be 16-bit aligned for 16-bit transfers) and how many bytes to
109 The final step is enabling the DMA channel and releasing the DMA
113 the channel again. You should also check get_dma_residue() to make
124 	set_dma_mode(channel, DMA_MODE_WRITE);
125 	set_dma_addr(channel, phys_addr);
126 	set_dma_count(channel, num_bytes);
128 	dma_enable(channel);
136 	dma_disable(channel);
138 	residue = dma_get_residue(channel);
146 --------------