b8fad3d029
This patch adds a mechanism to set aside a region of cache-coherent
(i.e. usually uncached) virtual memory, which can be used to communicate
with DMA devices without automatic cache snooping (common on ARM)
without the need of explicit flush/invalidation instructions in the
driver code.
This works by setting aside said region in the (board-specific) page
table setup, as exemplary done in this patch for the Snow and Pit
boards. It uses a new mechanism for adding board-specific Coreboot table
entries to describe this region in an entry with the LB_DMA tag.
Libpayload's memory allocator is enhanced to be able to operate on
distinct types/regions of memory. It provides dma_malloc() and
dma_memalign() functions for use in drivers, which by default just
operate on the same heap as their traditional counterparts. However, if
the Coreboot table parsing code finds a CB_DMA section, further requests
through the dma_xxx() functions will return memory from the region
described therein instead.
Change-Id: Ia9c249249e936bbc3eb76e7b4822af2230ffb186
Signed-off-by: Julius Werner <jwerner@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/167155
(cherry picked from commit
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| .. | ||
| assembler.h | ||
| cache.c | ||
| Config.in | ||
| coreboot.c | ||
| dummy_media.c | ||
| exception.c | ||
| exception_asm.S | ||
| head.S | ||
| libpayload.ldscript | ||
| main.c | ||
| Makefile.inc | ||
| memcpy.S | ||
| memset.S | ||
| sysinfo.c | ||
| timer.c | ||
| util.S | ||
| virtual.c | ||