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

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 d142ccdcd902a9d6ab4d495fbe6cbe85c61a5f01)
Signed-off-by: Isaac Christensen <isaac.christensen@se-eng.com>
Reviewed-on: http://review.coreboot.org/6622
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>

1 files changed, 16 insertions, 0 deletions

diff --git a/src/mainboard/google/pit/mainboard.c b/src/mainboard/google/pit/mainboard.c
index 77c54a189f..467b9d04e9 100644
--- a/src/mainboard/google/pit/mainboard.c
+++ b/src/mainboard/google/pit/mainboard.c
@@ -45,6 +45,10 @@
 #define DRAM_START	(CONFIG_SYS_SDRAM_BASE >> 20)
 #define DRAM_SIZE	CONFIG_DRAM_SIZE_MB
 
+/* Arbitrary range of DMA memory for depthcharge's drivers */
+#define DMA_START	(0x77300000)
+#define DMA_SIZE	(0x00100000)
+
 static struct edid edid = {
 	.ha = 1366,
 	.va = 768,
@@ -452,6 +456,7 @@ static void mainboard_enable(device_t dev)
 
 	/* set up caching for the DRAM */
 	mmu_config_range(DRAM_START, DRAM_SIZE, DCACHE_WRITEBACK);
+	mmu_config_range(DMA_START >> 20, DMA_SIZE >> 20, DCACHE_OFF);
 	tlb_invalidate_all();
 
 	/* this is going to move, but we must have it now and we're
@@ -472,3 +477,14 @@ struct chip_operations mainboard_ops = {
 	.name	= "Samsung/Google ARM Chromebook",
 	.enable_dev = mainboard_enable,
 };
+
+void lb_board(struct lb_header *header)
+{
+	struct lb_range *dma;
+
+	dma = (struct lb_range *)lb_new_record(header);
+	dma->tag = LB_TAB_DMA;
+	dma->size = sizeof(*dma);
+	dma->range_start = (intptr_t)DMA_START;
+	dma->range_size = DMA_SIZE;
+}