[RFC][PATCH 3/3] arm64: renesas: Add TFA BL31 handoff support

[Marek Vasut]

Implement custom U_BOOT_FIT_LOADABLE_HANDLER and armv8_switch_to_el2_prep()
handling in case the TFA was loaded. The loadables handler sets up custom
handoff structure used by Renesas TFA fork in fixed location in DRAM and
indicates the TFA has been loaded.

The custom armv8_switch_to_el2_prep() handling tests whether the TFA BL31
was previously loaded and the custom handoff structure was set up, and if
so, jumps to TFA BL31 which switches from EL3 to EL2 and then returns to
U-Boot just past bl in armv8_switch_to_el2() to finish starting the Linux
kernel.

The jump to Linux through TFA works in such a way that the custom
armv8_switch_to_el2_prep() handler configures the custom handoff structure
such that the target jump address of the TFA BL31 on exit is set to the
armv8_switch_to_el2() + 4, which is just past the bl, and just before the
U-Boot code which implements the Linux kernel boot from either EL. The
registers passed through the TFA BL31 are all the registers passed into
armv8_switch_to_el2_prep() to assure maximum compatibility with all the
boot modes. The armv8_switch_to_el2_prep() handler jumps to the TFA BL31,
which does its setup, drops EL from EL3 to EL2 and finally jumps to the
armv8_switch_to_el2() + 4 entry point, which then allows U-Boot to boot
the Linux kernel the usual way.

In order to build suitable kernel fitImage, build TFA first, temporarily
from downstream repository:
remote: https://github.com/renesas-rcar/arm-trusted-firmware.git
branch: rcar_gen4_v2.7_v4x

```
$ git clean -fqdx
$ MBEDTLS_DIR=/path/to/mbedtls/ make -j$(nproc) bl31 \
	PLAT=rcar_gen4 ARCH=aarch64 LSI=V4H SPD=none \
	CTX_INCLUDE_AARCH32_REGS=0 MBEDTLS_COMMON_MK=1 \
	PTP_NONSECURE_ACCESS=1 LOG_LEVEL=20 DEBUG=0 \
	ENABLE_ASSERTIONS=0 E=0
```

Build Linux kernel Image and device tree from current mainline Linux
kernel repository, obtain 'Image' and 'r8a779g0-white-hawk.dtb' .

Bundle the files together using provided fit-image.its fitImage description:
```
$ mkimage -f fit-image.its fitImage
```

To start the kernel fiImage generated in previous step, load fitImage
to DRAM and use the 'bootm' command to start it:
=> load 0x58000000 ... fitImage && bootm 0x58000000

Signed-off-by: Marek Vasut <marek.vasut+renesas at mailbox.org>
---
Cc: Andre Przywara <andre.przywara at arm.com>
Cc: Caleb Connolly <caleb.connolly at linaro.org>
Cc: Igor Opaniuk <igor.opaniuk at gmail.com>
Cc: Ilias Apalodimas <ilias.apalodimas at linaro.org>
Cc: Julien Masson <jmasson at baylibre.com>
Cc: Mattijs Korpershoek <mkorpershoek at baylibre.com>
Cc: Maxim Moskalets <maximmosk4 at gmail.com>
Cc: Michael Walle <mwalle at kernel.org>
Cc: Nobuhiro Iwamatsu <iwamatsu at nigauri.org>
Cc: Patrick Rudolph <patrick.rudolph at 9elements.com>
Cc: Paul Barker <paul.barker.ct at bp.renesas.com>
Cc: Paul-Erwan Rio <paulerwan.rio at gmail.com>
Cc: Peter Hoyes <Peter.Hoyes at arm.com>
Cc: Raymond Mao <raymond.mao at linaro.org>
Cc: Sam Protsenko <semen.protsenko at linaro.org>
Cc: Simon Glass <sjg at chromium.org>
Cc: Sughosh Ganu <sughosh.ganu at linaro.org>
Cc: Tom Rini <trini at konsulko.com>
Cc: u-boot at lists.denx.de
---
 board/renesas/rcar-common/gen4-common.c | 118 ++++++++++++++++++++++++
 1 file changed, 118 insertions(+)

diff --git a/board/renesas/rcar-common/gen4-common.c b/board/renesas/rcar-common/gen4-common.c
index 2abe9660cf8..2ca9fbe7851 100644
--- a/board/renesas/rcar-common/gen4-common.c
+++ b/board/renesas/rcar-common/gen4-common.c
@@ -7,11 +7,13 @@
 
 #include <asm/arch/renesas.h>
 #include <asm/arch/sys_proto.h>
+#include <asm/armv8/mmu.h>
 #include <asm/global_data.h>
 #include <asm/io.h>
 #include <asm/mach-types.h>
 #include <asm/processor.h>
 #include <asm/system.h>
+#include <image.h>
 #include <linux/errno.h>
 
 #define RST_BASE	0xE6160000 /* Domain0 */
@@ -88,3 +90,119 @@ int ft_board_setup(void *blob, struct bd_info *bd)
 {
 	return 0;
 }
+
+/* R-Car Gen4 TFA BL31 handoff structure and handling. */
+struct param_header {
+	u8			type;
+	u8			version;
+	u16			size;
+	u32			attr;
+};
+
+struct tfa_image_info {
+	struct param_header	h;
+	uintptr_t		image_base;
+	u32			image_size;
+	u32			image_max_size;
+};
+
+struct aapcs64_params {
+	u64			arg0;
+	u64			arg1;
+	u64			arg2;
+	u64			arg3;
+	u64			arg4;
+	u64			arg5;
+	u64			arg6;
+	u64			arg7;
+};
+
+struct entry_point_info {
+	struct param_header	h;
+	uintptr_t		pc;
+	u32			spsr;
+	struct aapcs64_params	args;
+};
+
+struct bl2_to_bl31_params_mem {
+	struct tfa_image_info	bl32_image_info;
+	struct tfa_image_info	bl33_image_info;
+	struct entry_point_info	bl33_ep_info;
+	struct entry_point_info	bl32_ep_info;
+};
+
+/* Default jump address, return to U-Boot */
+#define BL33_BASE	0x44100000
+/* Custom parameters address passed to TFA by ICUMXA loader */
+#define PARAMS_BASE	0x46422200
+
+/* Usually such a structure is produced by ICUMXA and passed in at 0x46422200 */
+static const struct bl2_to_bl31_params_mem blinfo_template = {
+	.bl33_ep_info.h.type = 1,	/* PARAM_EP */
+	.bl33_ep_info.h.version = 2,	/* Version 2 */
+	.bl33_ep_info.h.size = sizeof(struct entry_point_info),
+	.bl33_ep_info.h.attr = 0x81,	/* Executable | Non-Secure */
+	.bl33_ep_info.spsr = 0x2c9,	/* Mode=EL2, SP=ELX, Exceptions=OFF */
+	.bl33_ep_info.pc = BL33_BASE,
+
+	.bl33_image_info.h.type = 1,	/* PARAM_EP */
+	.bl33_image_info.h.version = 2,	/* Version 2 */
+	.bl33_image_info.h.size = sizeof(struct image_info),
+	.bl33_image_info.h.attr = 0,
+	.bl33_image_info.image_base = BL33_BASE,
+};
+
+static bool tfa_bl31_image_loaded;
+static ulong tfa_bl31_image_addr;
+
+static void tfa_bl31_image_process(ulong image, size_t size)
+{
+	/* Custom parameters address passed to TFA by ICUMXA loader */
+	struct bl2_to_bl31_params_mem *blinfo = (struct bl2_to_bl31_params_mem *)PARAMS_BASE;
+
+	/* Clear a page and copy template */
+	memset((void *)PARAMS_BASE, 0, PAGE_SIZE);
+	memcpy(blinfo, &blinfo_template, sizeof(*blinfo));
+	tfa_bl31_image_addr = image;
+	tfa_bl31_image_loaded = true;
+}
+
+U_BOOT_FIT_LOADABLE_HANDLER(IH_TYPE_TFA_BL31, tfa_bl31_image_process);
+
+void armv8_switch_to_el2_prep(u64 args, u64 mach_nr, u64 fdt_addr,
+			      u64 arg4, u64 entry_point, u64 es_flag)
+{
+	typedef void __noreturn (*image_entry_noargs_t)(void);
+	image_entry_noargs_t image_entry =
+		(image_entry_noargs_t)(void *)tfa_bl31_image_addr;
+	struct bl2_to_bl31_params_mem *blinfo =
+		(struct bl2_to_bl31_params_mem *)PARAMS_BASE;
+
+	/*
+	 * Destination address in arch/arm/cpu/armv8/transition.S
+	 * right past the first bl in armv8_switch_to_el2() to let
+	 * the rest of U-Boot pre-Linux code run. The code does run
+	 * without stack pointer!
+	 */
+	const u64 ep = ((u64)(uintptr_t)&armv8_switch_to_el2) + 4;
+
+	/* If TFA BL31 was not part of the fitImage, do regular boot. */
+	if (!tfa_bl31_image_loaded)
+		return;
+
+	/*
+	 * Set up kernel entry point and parameters:
+	 * x0 is FDT address, x1..x3 must be 0
+	 */
+	blinfo->bl33_ep_info.pc = ep;
+	blinfo->bl33_ep_info.args.arg0 = args;
+	blinfo->bl33_ep_info.args.arg1 = mach_nr;
+	blinfo->bl33_ep_info.args.arg2 = fdt_addr;
+	blinfo->bl33_ep_info.args.arg3 = arg4;
+	blinfo->bl33_ep_info.args.arg4 = entry_point;
+	blinfo->bl33_ep_info.args.arg5 = es_flag;
+	blinfo->bl33_image_info.image_base = ep;
+
+	/* Jump to TFA BL31 */
+	image_entry();
+}
-- 
2.45.2