[PATCH 0/5] Convert Lichee Pi 4A to use S-Mode proper U-Boot

[PATCH 0/5] Convert Lichee Pi 4A to use S-Mode proper U-Boot

[Yao Zi]

RISC-V software usually expects that HARTs are running under S mode when
leaving the firmware, for example, the UEFI specification explicitly
states requirements for S mode.

This series separates M-mode-only code for TH1520 port out, and
configures binman to pack the OpenSBI firmware to initialize the S-mode
environment. Then S-mode proper U-Boot is enabled on our Lichee Pi 4A
port.

Note that booting on Lichee Pi 4A is broken between PATCH 3 and 4,
affecting bisectability. Considering TH1520 port is still in an early
stage and separating the changes make the commit cleaner, I personally
consider it's acceptable.

Yao Zi (5):
  riscv: cpu: th1520: Build spl.c for SPL only
  riscv: cpu: th1520: Support cache enabling/disabling in M mode only
  riscv: dts: th1520: Prepare binman configuration for loading OpenSBI
  board: thead: licheepi4a: Run proper U-Boot in S-Mode
  doc: thead: lpi4a: Update for S-Mode proper U-Boot support

 arch/riscv/cpu/th1520/Makefile          |   2 +-
 arch/riscv/cpu/th1520/cache.c           |   2 +
 arch/riscv/dts/thead-th1520-binman.dtsi |  32 +++++-
 configs/th1520_lpi4a_defconfig          |   1 +
 doc/board/thead/lpi4a.rst               | 125 +++++++-----------------
 5 files changed, 68 insertions(+), 94 deletions(-)

-- 
2.49.0

[PATCH 1/5] riscv: cpu: th1520: Build spl.c for SPL only

[Yao Zi]

Symbols in spl.c only function correctly in SPL stage. Build the file
for SPL only to avoid weak symbols in proper U-Boot being unexpectedly
reloaded.

Fixes: 5fe9ced3552 ("riscv: cpu: Add TH1520 CPU support")
Signed-off-by: Yao Zi <ziyao@disroot.org>
---
 arch/riscv/cpu/th1520/Makefile | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/riscv/cpu/th1520/Makefile b/arch/riscv/cpu/th1520/Makefile
index 5d806c06e2e..d971ea7390d 100644
--- a/arch/riscv/cpu/th1520/Makefile
+++ b/arch/riscv/cpu/th1520/Makefile
@@ -5,4 +5,4 @@
 obj-y += cache.o
 obj-y += cpu.o
 obj-y += dram.o
-obj-y += spl.o
+obj-$(CONFIG_SPL_BUILD) += spl.o
-- 
2.49.0

Re: [PATCH 1/5] riscv: cpu: th1520: Build spl.c for SPL only

[Leo Liang]

On Fri, May 30, 2025 at 09:48:47AM +0000, Yao Zi wrote:
> [EXTERNAL MAIL]
> 
> Symbols in spl.c only function correctly in SPL stage. Build the file
> for SPL only to avoid weak symbols in proper U-Boot being unexpectedly
> reloaded.
> 
> Fixes: 5fe9ced3552 ("riscv: cpu: Add TH1520 CPU support")
> Signed-off-by: Yao Zi <ziyao@disroot.org>
> ---
>  arch/riscv/cpu/th1520/Makefile | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

Reviewed-by: Leo Yu-Chi Liang <ycliang@andestech.com>

[PATCH 2/5] riscv: cpu: th1520: Support cache enabling/disabling in M mode only

[Yao Zi]

These operations rely on a customized M-mode CSR, MHCR, which isn't
available when running in S mode.

Let's fallback to the generic weak stub when running in S mode to avoid
illegal accesses.

Signed-off-by: Yao Zi <ziyao@disroot.org>
---
 arch/riscv/cpu/th1520/cache.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/riscv/cpu/th1520/cache.c b/arch/riscv/cpu/th1520/cache.c
index 08aa1f789fd..b2fec229363 100644
--- a/arch/riscv/cpu/th1520/cache.c
+++ b/arch/riscv/cpu/th1520/cache.c
@@ -11,6 +11,7 @@
 #define  CSR_MHCR_IE		BIT(0)
 #define  CSR_MHCR_DE		BIT(1)
 
+#if CONFIG_IS_ENABLED(RISCV_MMODE)
 void icache_enable(void)
 {
 	csr_write(CSR_MHCR, csr_read(CSR_MHCR) | CSR_MHCR_IE);
@@ -30,3 +31,4 @@ int dcache_status(void)
 {
 	return (csr_read(CSR_MHCR) & CSR_MHCR_DE) != 0;
 }
+#endif /* CONFIG_IS_ENABLED(RISCV_MMODE) */
-- 
2.49.0

Re: [PATCH 2/5] riscv: cpu: th1520: Support cache enabling/disabling in M mode only

[Leo Liang]

On Fri, May 30, 2025 at 09:48:48AM +0000, Yao Zi wrote:
> [EXTERNAL MAIL]
> 
> These operations rely on a customized M-mode CSR, MHCR, which isn't
> available when running in S mode.
> 
> Let's fallback to the generic weak stub when running in S mode to avoid
> illegal accesses.
> 
> Signed-off-by: Yao Zi <ziyao@disroot.org>
> ---
>  arch/riscv/cpu/th1520/cache.c | 2 ++
>  1 file changed, 2 insertions(+)

Reviewed-by: Leo Yu-Chi Liang <ycliang@andestech.com>

[PATCH 3/5] riscv: dts: th1520: Prepare binman configuration for loading OpenSBI

[Yao Zi]

Add an OpenSBI entry to the FIT image. As it expects an FDT to be
passed, corresponding FDT entry is generated with of-list as well.

As SPL now passes a full FDT for following stages, proper U-Boot image
is packed into u-boot-with-spl.bin without a devicetree copy included.

Signed-off-by: Yao Zi <ziyao@disroot.org>
---
 arch/riscv/dts/thead-th1520-binman.dtsi | 32 +++++++++++++++++++++----
 1 file changed, 28 insertions(+), 4 deletions(-)

diff --git a/arch/riscv/dts/thead-th1520-binman.dtsi b/arch/riscv/dts/thead-th1520-binman.dtsi
index f060639e1c6..7b535e8402c 100644
--- a/arch/riscv/dts/thead-th1520-binman.dtsi
+++ b/arch/riscv/dts/thead-th1520-binman.dtsi
@@ -30,24 +30,48 @@
 		fit,fdt-list = "of-list";
 
 		images {
+			opensbi {
+				description = "OpenSBI fw_dynamic Firmware";
+				type = "firmware";
+				os = "opensbi";
+				arch = "riscv";
+				load = /bits/ 64 <CONFIG_SPL_OPENSBI_LOAD_ADDR>;
+				entry = /bits/ 64 <CONFIG_SPL_OPENSBI_LOAD_ADDR>;
+
+				opensbi_blob: opensbi {
+					filename = "fw_dynamic.bin";
+					missing-msg = "opensbi";
+				};
+			};
+
 			uboot {
 				description = "U-Boot";
 				type = "standalone";
+				firmware = "opensbi";
 				os = "U-boot";
 				arch = "riscv";
 				compression = "none";
 				load = /bits/ 64 <CONFIG_TEXT_BASE>;
 
-				uboot_blob: u-boot {
+				uboot_nodtb_blob: u-boot-nodtb {
 				};
 			};
+
+			@fdt-SEQ {
+				fit,operation = "gen-fdt-nodes";
+				description = "NAME";
+				type = "flat_dt";
+				compression = "none";
+			};
 		};
 
 		configurations {
-			default = "conf-th1520-lichee-pi-4a";
+			default = "@conf-DEFAULT-SEQ";
 
-			conf-th1520-lichee-pi-4a {
-				description = "th1520-lichee-pi-4a";
+			@conf-SEQ {
+				description = "NAME";
+				fdt = "fdt-SEQ";
+				firmware = "opensbi";
 				loadables = "uboot";
 			};
 		};
-- 
2.49.0

Re: [PATCH 3/5] riscv: dts: th1520: Prepare binman configuration for loading OpenSBI

[Leo Liang]

On Fri, May 30, 2025 at 09:48:49AM +0000, Yao Zi wrote:
> [EXTERNAL MAIL]
> 
> Add an OpenSBI entry to the FIT image. As it expects an FDT to be
> passed, corresponding FDT entry is generated with of-list as well.
> 
> As SPL now passes a full FDT for following stages, proper U-Boot image
> is packed into u-boot-with-spl.bin without a devicetree copy included.
> 
> Signed-off-by: Yao Zi <ziyao@disroot.org>
> ---
>  arch/riscv/dts/thead-th1520-binman.dtsi | 32 +++++++++++++++++++++----
>  1 file changed, 28 insertions(+), 4 deletions(-)

Reviewed-by: Leo Yu-Chi Liang <ycliang@andestech.com>

[PATCH 4/5] board: thead: licheepi4a: Run proper U-Boot in S-Mode

[Yao Zi]

RISC-V software usually expects S mode when leaving the firmware, e.g.
UEFI applications could only run in S mode. Let's convert proper U-Boot
of Lichee Pi 4A port to run in S mode.

Signed-off-by: Yao Zi <ziyao@disroot.org>
---
 configs/th1520_lpi4a_defconfig | 1 +
 1 file changed, 1 insertion(+)

diff --git a/configs/th1520_lpi4a_defconfig b/configs/th1520_lpi4a_defconfig
index b19dc009fde..32b39b295a8 100644
--- a/configs/th1520_lpi4a_defconfig
+++ b/configs/th1520_lpi4a_defconfig
@@ -11,6 +11,7 @@ CONFIG_SYS_LOAD_ADDR=0x80200000
 # CONFIG_SMP is not set
 CONFIG_TARGET_TH1520_LPI4A=y
 CONFIG_ARCH_RV64I=y
+CONFIG_RISCV_SMODE=y
 CONFIG_OF_BOARD_FIXUP=y
 CONFIG_SYS_BOOT_GET_CMDLINE=y
 CONFIG_SYS_BOOT_GET_KBD=y
-- 
2.49.0

Re: [PATCH 4/5] board: thead: licheepi4a: Run proper U-Boot in S-Mode

[Leo Liang]

On Fri, May 30, 2025 at 09:48:50AM +0000, Yao Zi wrote:
> [EXTERNAL MAIL]
> 
> RISC-V software usually expects S mode when leaving the firmware, e.g.
> UEFI applications could only run in S mode. Let's convert proper U-Boot
> of Lichee Pi 4A port to run in S mode.
> 
> Signed-off-by: Yao Zi <ziyao@disroot.org>
> ---
>  configs/th1520_lpi4a_defconfig | 1 +
>  1 file changed, 1 insertion(+)

Reviewed-by: Leo Yu-Chi Liang <ycliang@andestech.com>

[PATCH 5/5] doc: thead: lpi4a: Update for S-Mode proper U-Boot support

[Yao Zi]

Proper U-Boot for Lichee Pi 4A now runs in S mode instead of M mode,
which means the extra firmware, OpenSBI, must be built and integrated
in the image, and the vendor U-Boot cannot chainload the result image
anymore as it runs in M mode.

Remove redundant information about chainloading and update build steps
to mention OpenSBI firmware.

Signed-off-by: Yao Zi <ziyao@disroot.org>
---
 doc/board/thead/lpi4a.rst | 125 +++++++++++---------------------------
 1 file changed, 36 insertions(+), 89 deletions(-)

diff --git a/doc/board/thead/lpi4a.rst b/doc/board/thead/lpi4a.rst
index 7e4c4ea81ee..acd7ac2698d 100644
--- a/doc/board/thead/lpi4a.rst
+++ b/doc/board/thead/lpi4a.rst
@@ -55,123 +55,70 @@ DDR driver requires a firmware to function, to build it:
 	cd th1520-firmware
 	lua5.4 ddr-generate.lua src/<CONFIGURATION_NAME>.lua th1520-ddr-firmware.bin
 
-4. Build U-Boot images
+4. Build OpenSBI Firmware
 
-The U-Boot is capable of running in M-Mode, so we can directly build it without
-OpenSBI. The DDR firmware should be copied to U-Boot source directory before
+TH1520 port of proper U-Boot runs in S mode, thus OpenSBI is required as
+SBI firmware to setup S-mode environment and provide SBI calls. It could
+be cloned and built for TH1520 as below,
+
+.. code-block:: bash
+
+	git clone https://github.com/riscv-software-src/opensbi.git
+	cd opensbi
+	make PLATFORM=generic
+
+TH1520 support in OpenSBI requires v1.2 or a more recent version.
+
+More detailed description of steps required to build fw_dynamic firmware
+is beyond the scope of this document. Please refer to OpenSBI
+documenation.
+
+5. Build U-Boot images
+
+The DDR firmware should be copied to U-Boot source directory before
 building.
 
-.. code-block:: console
+.. code-block:: bash
 
 	cd <U-Boot-dir>
 	cp <path-to-ddr-firmware> th1520-ddr-firmware.bin
 	make th1520_lpi4a_defconfig
-	make
+	make OPENSBI=<opensbi_dir>/build/platform/generic/firmware/fw_dynamic.bin
 
-This will generate u-boot-dtb.bin and u-boot-with-spl.bin. The former contains
-only proper U-Boot and is for chainloading; the later contains also SPL and
-DDR firmware and is ready for booting by BROM directly.
+This will generate u-boot-with-spl.bin, which contains SPL, DDR firmware,
+OpenSBI firmware and proper U-Boot.
 
 Booting
 ~~~~~~~
 
-Currently, we rely on vendor u-boot to initialize the clock, pinctrl subsystem,
-and chain load the mainline u-boot image either via tftp or emmc storage,
-then bootup from it.
-
-Sample boot log from Lichee PI 4A board via tftp
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-
-.. code-block:: none
-
-	brom_ver 8
-	[APP][E] protocol_connect failed, exit.
-
-	U-Boot SPL 2020.01-00016-g8c870a6be8 (May 20 2023 - 01:04:49 +0000)
-	FM[1] lpddr4x dualrank freq=3733 64bit dbi_off=n sdram init
-	ddr initialized, jump to uboot
-	image has no header
+u-boot-with-spl.bin should be loaded to SRAM through fastboot. Connect
+the board to computer with Type-C cable and run
 
+.. code-block:: bash
 
-	U-Boot 2020.01-00016-g8c870a6be8 (May 20 2023 - 01:04:49 +0000)
+	fastboot flash ram u-boot-with-spl.bin
+	fastboot reboot
 
-	CPU:   rv64imafdcvsu
-	Model: T-HEAD c910 light
-	DRAM:  8 GiB
-	C910 CPU FREQ: 750MHz
-	AHB2_CPUSYS_HCLK FREQ: 250MHz
-	AHB3_CPUSYS_PCLK FREQ: 125MHz
-	PERISYS_AHB_HCLK FREQ: 250MHz
-	PERISYS_APB_PCLK FREQ: 62MHz
-	GMAC PLL POSTDIV FREQ: 1000MHZ
-	DPU0 PLL POSTDIV FREQ: 1188MHZ
-	DPU1 PLL POSTDIV FREQ: 1188MHZ
-	MMC:   sdhci@ffe7080000: 0, sd@ffe7090000: 1
-	Loading Environment from MMC... OK
-	Error reading output register
-	Warning: cannot get lcd-en GPIO
-	LCD panel cannot be found : -121
-	splash screen startup cost 16 ms
-	In:    serial
-	Out:   serial
-	Err:   serial
-	Net:
-	Warning: ethernet@ffe7070000 using MAC address from ROM
-	eth0: ethernet@ffe7070000ethernet@ffe7070000:0 is connected to ethernet@ffe7070000.  Reconnecting to ethernet@ffe7060000
-
-	Warning: ethernet@ffe7060000 (eth1) using random MAC address - 42:25:d4:16:5f:fc
-	, eth1: ethernet@ffe7060000
-	Hit any key to stop autoboot:  2
-	ethernet@ffe7060000 Waiting for PHY auto negotiation to complete.. done
-	Speed: 1000, full duplex
-	Using ethernet@ffe7070000 device
-	TFTP from server 192.168.8.50; our IP address is 192.168.8.45
-	Filename 'u-boot-dtb.bin'.
-	Load address: 0x1c00000
-	Loading: * #########################
-		 8 MiB/s
-	done
-	Bytes transferred = 376686 (5bf6e hex)
-	## Starting application at 0x01C00000 ...
-
-        U-Boot 2023.07-rc2-00004-g1befbe31c1 (May 23 2023 - 18:40:01 +0800)
-
-        CPU:   rv64imafdc
-        Model: Sipeed Lichee Pi 4A
-        DRAM:  8 GiB
-        Core:  13 devices, 6 uclasses, devicetree: separate
-        Loading Environment from <NULL>... OK
-        In:    serial@ffe7014000
-        Out:   serial@ffe7014000
-        Err:   serial@ffe7014000
-        Model: Sipeed Lichee Pi 4A
-        LPI4A=>
-
-SPL support is still in an early stage and not all of the functionalities are
-available when booting from mainline SPL. When using mainline SPL,
-u-boot-with-spl.bin should be loaded to SRAM through fastboot.
-
-Sample boot log from Lichee PI 4A board via fastboot and mainline SPL
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+Sample boot log from Lichee PI 4A board via fastboot
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 .. code-block:: none
 
-	brom_ver 8
 	[APP][E] protocol_connect failed, exit.
-	Starting download of 636588 bytes
+	Starting download of 940681 bytes
 
-	downloading of 636588 bytes finished
+	downloading of 940681 bytes finished
 
-	U-Boot SPL 2025.04-rc2-00049-geaa9fc99d4cd-dirty (Apr 26 2025 - 13:31:41 +0000)
+	U-Boot SPL 2025.07-rc3-00005-g3a0ef515b8bb (May 29 2025 - 10:42:46 +0000)
 	Trying to boot from RAM
 
 
-	U-Boot 2025.04-rc2-00049-geaa9fc99d4cd-dirty (Apr 26 2025 - 13:31:41 +0000)
+	U-Boot 2025.07-rc3-00005-g3a0ef515b8bb (May 29 2025 - 10:42:46 +0000)
 
 	CPU:   thead,c910
 	Model: Sipeed Lichee Pi 4A
 	DRAM:  8 GiB
-	Core:  30 devices, 9 uclasses, devicetree: separate
+	Core:  110 devices, 9 uclasses, devicetree: separate
 	MMC:   mmc@ffe7080000: 0, mmc@ffe7090000: 1
 	Loading Environment from <NULL>... OK
 	In:    serial@ffe7014000
-- 
2.49.0

Re: [PATCH 5/5] doc: thead: lpi4a: Update for S-Mode proper U-Boot support

[Leo Liang]

On Fri, May 30, 2025 at 09:48:51AM +0000, Yao Zi wrote:
> [EXTERNAL MAIL]
> 
> Proper U-Boot for Lichee Pi 4A now runs in S mode instead of M mode,
> which means the extra firmware, OpenSBI, must be built and integrated
> in the image, and the vendor U-Boot cannot chainload the result image
> anymore as it runs in M mode.
> 
> Remove redundant information about chainloading and update build steps
> to mention OpenSBI firmware.
> 
> Signed-off-by: Yao Zi <ziyao@disroot.org>
> ---
>  doc/board/thead/lpi4a.rst | 125 +++++++++++---------------------------
>  1 file changed, 36 insertions(+), 89 deletions(-)

Reviewed-by: Leo Yu-Chi Liang <ycliang@andestech.com>

Re: [PATCH 0/5] Convert Lichee Pi 4A to use S-Mode proper U-Boot

[Tom Plant]

For what it's worth, tested with OpenSBI 1.6 on a Lichee Pi 4A 8GB.
Tested-by: Tom Plant <tom@tplant.com.au>

Re: [PATCH 0/5] Convert Lichee Pi 4A to use S-Mode proper U-Boot

[Ricardo B. Marlière]

On Fri May 30, 2025 at 6:48 AM -03, Yao Zi wrote:
> RISC-V software usually expects that HARTs are running under S mode when
> leaving the firmware, for example, the UEFI specification explicitly
> states requirements for S mode.
>
> This series separates M-mode-only code for TH1520 port out, and
> configures binman to pack the OpenSBI firmware to initialize the S-mode
> environment. Then S-mode proper U-Boot is enabled on our Lichee Pi 4A
> port.
>
> Note that booting on Lichee Pi 4A is broken between PATCH 3 and 4,
> affecting bisectability. Considering TH1520 port is still in an early
> stage and separating the changes make the commit cleaner, I personally
> consider it's acceptable.
>
> Yao Zi (5):
>   riscv: cpu: th1520: Build spl.c for SPL only
>   riscv: cpu: th1520: Support cache enabling/disabling in M mode only
>   riscv: dts: th1520: Prepare binman configuration for loading OpenSBI
>   board: thead: licheepi4a: Run proper U-Boot in S-Mode
>   doc: thead: lpi4a: Update for S-Mode proper U-Boot support
>
>  arch/riscv/cpu/th1520/Makefile          |   2 +-
>  arch/riscv/cpu/th1520/cache.c           |   2 +
>  arch/riscv/dts/thead-th1520-binman.dtsi |  32 +++++-
>  configs/th1520_lpi4a_defconfig          |   1 +
>  doc/board/thead/lpi4a.rst               | 125 +++++++-----------------
>  5 files changed, 68 insertions(+), 94 deletions(-)

I also tested with OpenSBI 1.6 on a Lichee Pi 4A 8GB.

Tested-by: Ricardo B. Marlière <ricardo@marliere.net>