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arm: libpayload: Add cache coherent DMA memory definition and management

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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, Pit and Kirby
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.

BUG=chrome-os-partner:21969
TEST=Manual

Change-Id: Ia9c249249e936bbc3eb76e7b4822af2230ffb186
Signed-off-by: Julius Werner <jwerner@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/167155
This commit is contained in:
Julius Werner 2013-08-27 15:48:32 -07:00 • committed by Caroline Tice
commit d142ccdcd9
9 changed files with 158 additions and 42 deletions
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7
src/lib/coreboot_table.c
View file

@ -79,7 +79,7 @@ static struct lb_record *lb_last_record(struct lb_header *header)
return rec;
}
static struct lb_record *lb_new_record(struct lb_header *header)
struct lb_record *lb_new_record(struct lb_header *header)
{
struct lb_record *rec;
rec = lb_last_record(header);
@ -364,6 +364,8 @@ static void lb_strings(struct lb_header *header)
}
void __attribute__((weak)) lb_board(struct lb_header *header) { /* NOOP */ }
static struct lb_forward *lb_forward(struct lb_header *header, struct lb_header *next_header)
{
struct lb_record *rec;
@ -576,6 +578,9 @@ unsigned long write_coreboot_table(
#endif
add_cbmem_pointers(head);
/* Add board-specific table entries, if any. */
lb_board(head);
/* Remember where my valid memory ranges are */
return lb_table_fini(head);
}