arch/arm: Enable FIT payloads

Implements fit_payload_arch for the arm (aarch32) architecture, so that
FIT images can be used. The implementation is very similar to the
existing implementations for arm64 and riscv, and has mostly been
lifted from these other ports.

TEST: Booted Beaglebone Black (in progress port, to be submitted soon!)
with a FIT image containing a 5.4 kernel, dtb and initramfs.

Change-Id: I6b50c6f06b83c00a5b3622b5bbafe67130b6d233
Signed-off-by: Sam Lewis <sam.vr.lewis@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/44377
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Julius Werner <jwerner@chromium.org>

2 files changed, 91 insertions, 0 deletions

diff --git a/src/arch/arm/Makefile.inc b/src/arch/arm/Makefile.inc
index eef2650685..241bfe5051 100644
--- a/src/arch/arm/Makefile.inc
+++ b/src/arch/arm/Makefile.inc
@@ -119,6 +119,7 @@ ramstage-y += memset.S
 ramstage-y += memcpy.S
 ramstage-y += memmove.S
 ramstage-y += clock.c
+ramstage-$(CONFIG_PAYLOAD_FIT_SUPPORT) += fit_payload.c
 
 rmodules_arm-y += memset.S
 rmodules_arm-y += memcpy.S
diff --git a/src/arch/arm/fit_payload.c b/src/arch/arm/fit_payload.c
new file mode 100644
index 0000000000..f5470071d4
--- /dev/null
+++ b/src/arch/arm/fit_payload.c
@@ -0,0 +1,90 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+#include <console/console.h>
+#include <bootmem.h>
+#include <program_loading.h>
+#include <fit.h>
+#include <symbols.h>
+
+/**
+ * Place the region in free memory range.
+ */
+static bool fit_place_mem(const struct range_entry *r, void *arg)
+{
+	struct region *region = arg;
+	resource_t start;
+
+	if (range_entry_tag(r) != BM_MEM_RAM)
+		return true;
+
+	/* Linux 4.15 doesn't like 4KiB alignment. Align to 1 MiB for now. */
+	start = ALIGN_UP(MAX(region->offset, range_entry_base(r)), 1 * MiB);
+
+	if (start + region->size < range_entry_end(r)) {
+		region->offset = (size_t)start;
+		return false;
+	}
+
+	return true;
+}
+
+
+bool fit_payload_arch(struct prog *payload, struct fit_config_node *config,
+		      struct region *kernel,
+		      struct region *fdt,
+		      struct region *initrd)
+{
+	void *arg = NULL;
+
+	/**
+	 * The kernel ARM documentation recommends loading the kernel above 32MiB
+	 * in order to avoid the need to need to relocate prior to decompression.
+	 */
+	kernel->offset = (uintptr_t)_dram + 32 * MiB;
+
+	/**
+	 * The code assumes that bootmem_walk provides a sorted list of memory
+	 * regions, starting from the lowest address.
+	 * The order of the calls here doesn't matter, as the placement is
+	 * enforced in the called functions.
+	 * For details check code on top.
+	 */
+	if (!bootmem_walk(fit_place_mem, kernel))
+		return false;
+
+	/* Mark as reserved for future allocations. */
+	bootmem_add_range(kernel->offset, kernel->size, BM_MEM_PAYLOAD);
+
+	/**
+	 * To ensure the fdt is not overwritten by the kernel decompressor, place
+	 * the fdt above the 128 MB from the start of RAM, as recommended by the
+	 * kernel documentation.
+	 */
+	fdt->offset = (uintptr_t)_dram + 128 * MiB;
+
+	if (!bootmem_walk(fit_place_mem, fdt))
+		return false;
+
+	/* Mark as reserved for future allocations. */
+	bootmem_add_range(fdt->offset, fdt->size, BM_MEM_PAYLOAD);
+
+	/* Place INITRD */
+	if (config->ramdisk) {
+		initrd->offset = fdt->offset + fdt->size;
+
+		if (!bootmem_walk(fit_place_mem, initrd))
+			return false;
+
+		/* Mark as reserved for future allocations. */
+		bootmem_add_range(initrd->offset, initrd->size, BM_MEM_PAYLOAD);
+	}
+
+	/* Kernel expects FDT as argument */
+	arg = (void *)fdt->offset;
+
+	prog_set_entry(payload, (void *)kernel->offset, arg);
+
+	bootmem_dump_ranges();
+
+	return true;
+}