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>

4 files changed, 101 insertions, 2 deletions

diff --git a/Documentation/lib/payloads/fit.md b/Documentation/lib/payloads/fit.md
index c6ccc7b868f3..ef5e892c36c0 100644
--- a/Documentation/lib/payloads/fit.md
+++ b/Documentation/lib/payloads/fit.md
@@ -5,6 +5,7 @@
 
 ## Supported architectures
 
+* aarch32
 * aarch64
 * riscv
 
@@ -26,6 +27,13 @@ The section must be named in order to be found by the FIT parser:
 
 The FIT parser needs architecure support.
 
+### aarch32
+The source code can be found in `src/arch/arm/fit_payload.c`.
+
+On aarch32 the kernel (a section named 'kernel') must be in **Image**
+format and it needs a devicetree (a section named 'fdt') to boot.
+The kernel will be placed close to "*DRAMSTART*".
+
 ### aarch64
 The source code can be found in `src/arch/arm64/fit_payload.c`.
 
diff --git a/payloads/Kconfig b/payloads/Kconfig
index cfb28d6e81df..627bb95c9c19 100644
--- a/payloads/Kconfig
+++ b/payloads/Kconfig
@@ -30,7 +30,7 @@ config PAYLOAD_ELF
 
 config PAYLOAD_FIT
 	bool "A FIT payload"
-	depends on ARCH_ARM64 || ARCH_RISCV
+	depends on ARCH_ARM64 || ARCH_RISCV || ARCH_ARM
 	select PAYLOAD_FIT_SUPPORT
 	help
 	  Select this option if you have a payload image (a FIT file) which
@@ -97,7 +97,7 @@ config PAYLOAD_FIT_SUPPORT
 	bool "FIT support"
 	default n
 	default y if PAYLOAD_LINUX && (ARCH_ARM || ARCH_ARM64 || ARCH_RISCV)
-	depends on ARCH_ARM64 || ARCH_RISCV
+	depends on ARCH_ARM64 || ARCH_RISCV || ARCH_ARM
 	select FLATTENED_DEVICE_TREE
 	help
 	  Select this option if your payload is of type FIT.
diff --git a/src/arch/arm/Makefile.inc b/src/arch/arm/Makefile.inc
index eef26506852c..241bfe50517c 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 000000000000..f5470071d437
--- /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;
+}