libpayload arm64: Initialize and enable MMU

What this change does:
1) Initialize limited page tables as soon as we jump into libpayload. Basically
two ranges are initialized. One is for the BASE_ADDRESS and other is for the
coreboot_tables. With page tables initialized and MMU enabled, we jump into
code to parse coreboot tables.
2) Once coreboot tables are parsed and we have complete picture of the memory,
we perform a complete page table initialzation and enable MMU and then jump to
payload.

Additionally, we also:
1) Initialize DMA memory on our own depending upon the memory map. It ensures
that the DMA buffer is placed in 32-bit memory.

CQ-DEPEND=CL:216826
BUG=chrome-os-partner:31634
BRANCH=None
TEST=Compiles successfully and we are able to start execution of libpayload in
EL2 and reach kernel login prompt

Change-Id: Ie0f47b7759d4ac65a6920f7f2f7502b889afda6d
Signed-off-by: Furquan Shaikh <furquan@google.com>
Reviewed-on: https://chromium-review.googlesource.com/216824
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Tested-by: Furquan Shaikh <furquan@chromium.org>
Commit-Queue: Furquan Shaikh <furquan@chromium.org>

payloads/libpayload/arch/arm64/main.c

@@ -29,6 +29,7 @@
 
 #include <exception.h>
 #include <libpayload.h>
+#include <arch/mmu.h>
 
 unsigned int main_argc;    /**< The argc value to pass to main() */
 
@@ -48,6 +49,64 @@ static int test_exception(void)
 	return 0;
 }
 
+/*
+ * Func: pre_sysinfo_scan_mmu_setup
+ * Desc: We need to setup and enable MMU before we can go to scan coreboot
+ * tables. However, we are not sure what all memory regions to map. Thus,
+ * initializing minimum required memory ranges
+ */
+static void pre_sysinfo_scan_mmu_setup(void)
+{
+	uint64_t start = (uint64_t)&_start;
+	uint64_t end = (uint64_t)&_end;
+
+	/* Memory range 1: Covers the area occupied by payload */
+	mmu_presysinfo_memory_used(start, end - start);
+
+	/*
+	 * Memory range 2: Coreboot tables
+	 *
+	 * Maximum size is assumed 2 pages in case it crosses the GRANULE_SIZE
+	 * boundary
+	 */
+	mmu_presysinfo_memory_used((uint64_t)get_cb_header_ptr(),
+				   2 * GRANULE_SIZE);
+
+	mmu_presysinfo_enable();
+}
+
+/*
+ * Func: post_sysinfo_scan_mmu_setup
+ * Desc: Once we have scanned coreboot tables, we have complete information
+ * about different memory ranges. Thus, we can perform a complete mmu
+ * initialization. Also, this takes care of DMA area setup
+ */
+static void post_sysinfo_scan_mmu_setup(void)
+{
+	struct memrange *ranges;
+	uint64_t nranges;
+	struct mmu_ranges mmu_ranges;
+	struct mmu_memrange *dma_range;
+
+	/* Get memrange info from lib_sysinfo */
+	lib_sysinfo_get_memranges(&ranges, &nranges);
+
+	/* Get memory ranges for mmu init from lib_sysinfo memrange */
+	dma_range = mmu_init_ranges_from_sysinfo(ranges, nranges, &mmu_ranges);
+
+	/* Disable mmu */
+	mmu_disable();
+
+	/* Init mmu */
+	mmu_init(&mmu_ranges);
+
+	/* Enable mmu */
+	mmu_enable();
+
+	/* Init dma memory */
+	init_dma_memory((void *)dma_range->base, dma_range->size);
+}
+
 /**
  * This is our C entry function - set up the system
  * and jump into the payload entry point.
@@ -57,12 +116,17 @@ void start_main(void)
 {
 	extern int main(int argc, char **argv);
 
+	pre_sysinfo_scan_mmu_setup();
+
 	/* Gather system information. */
 	lib_get_sysinfo();
 
 #ifndef CONFIG_LP_SKIP_CONSOLE_INIT
 	console_init();
 #endif
+
+	post_sysinfo_scan_mmu_setup();
+
 	printf("ARM64: Libpayload %s\n",__func__);
 	exception_init();