[PATCH v2 0/4] Simplify retrieving FDT from SBI in S-Mode

[PATCH v2 0/4] Simplify retrieving FDT from SBI in S-Mode

[Yao Zi]

A typical bootflow of S-Mode RISC-V U-Boot looks like,

  -------    -------    ----------
  | SPL | -> | SBI | -> | U-Boot |
  -------    -------    ----------
                |
     M-Mode     |       S-Mode
                |

Both the most popular SBI implementation, OpenSBI, and U-Boot require a
FDT to function. The common solution is to pick an appropriate
devicetree at SPL stage and pass it to OpenSBI, which is also capable of
passing its (possibly modified) devicetree to the next stage (proper
U-Boot here) program.

The problem is although we retrieve the FDT passed by SBI in RISC-V's
start.S, a custom board_fdt_blob_setup is still required to make use of
it, resulting in duplicated similar functions in board-level code.

This series provides a weak version of board_fdt_blob_setup to setup the
SBI-passed FDT, serving as fallback on RISC-V platforms to eliminate the
duplication.

Tested on
 - Milk-V Duo (milkv_duo_defconfig)
 - Starfive VisionFive 2 (starfive_visionfive2_defconfig)
 - QEMU VM (qemu-riscv64_smode_defconfig, sifive_unleashed_defconfig).

Changed from v1
- make the default implementation bail out in XPL stage
- correct commit message of sifive platform chagnes
- don't enable OF_HAS_PRIOR_STAGE by default on all SBI-capable RISC-V
  platforms, as it may break the binman configuration
- Link to v1: https://lore.kernel.org/u-boot/20250227144734.61458-1-ziyao@disroot.org/

Yao Zi (4):
  riscv: lib: Add a default implementation of board_fdt_blob_setup
  board: qemu: riscv: Remove duplicated board_fdt_blob_setup
  board: starfive: Remove duplicated board_fdt_blob_setup
  board: sifive: Remove dead board_fdt_blob_setup

 arch/riscv/lib/Makefile                       |  1 +
 arch/riscv/lib/board.c                        | 19 +++++++++++++++++++
 board/emulation/qemu-riscv/qemu-riscv.c       |  8 --------
 board/sifive/unleashed/unleashed.c            | 11 -----------
 board/sifive/unmatched/unmatched.c            | 10 ----------
 .../visionfive2/starfive_visionfive2.c        | 10 ----------
 6 files changed, 20 insertions(+), 39 deletions(-)
 create mode 100644 arch/riscv/lib/board.c

-- 
2.48.1

[PATCH v2 1/4] riscv: lib: Add a default implementation of board_fdt_blob_setup

[Yao Zi]

It's common for S-Mode proper U-Boot to retrieve a FDT blob along with
taking control from SBI firmware. Add a weak version of
board_fdt_blob_setup to make use of it by default, avoiding copy-pasting
similar functions among boards.

Signed-off-by: Yao Zi <ziyao@disroot.org>
---
 arch/riscv/lib/Makefile |  1 +
 arch/riscv/lib/board.c  | 19 +++++++++++++++++++
 2 files changed, 20 insertions(+)
 create mode 100644 arch/riscv/lib/board.c

diff --git a/arch/riscv/lib/Makefile b/arch/riscv/lib/Makefile
index 268116f3757..b33f9c646dd 100644
--- a/arch/riscv/lib/Makefile
+++ b/arch/riscv/lib/Makefile
@@ -27,6 +27,7 @@ obj-$(CONFIG_$(XPL_)SMP) += smp.o
 obj-$(CONFIG_XPL_BUILD)	+= spl.o
 obj-y   += fdt_fixup.o
 obj-$(CONFIG_$(SPL)CMD_BDI) += bdinfo.o
+obj-$(CONFIG_OF_BOARD) += board.o
 
 # For building EFI apps
 CFLAGS_NON_EFI := -fstack-protector-strong
diff --git a/arch/riscv/lib/board.c b/arch/riscv/lib/board.c
new file mode 100644
index 00000000000..1630355b2b1
--- /dev/null
+++ b/arch/riscv/lib/board.c
@@ -0,0 +1,19 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * RISC-V-specific handling of firmware FDT
+ */
+
+#include <asm/global_data.h>
+#include <linux/errno.h>
+
+DECLARE_GLOBAL_DATA_PTR;
+
+__weak int board_fdt_blob_setup(void **fdtp)
+{
+	if (IS_ENABLED(CONFIG_XPL_BUILD) || !gd->arch.firmware_fdt_addr)
+		return -EEXIST;
+
+	*fdtp = (void *)gd->arch.firmware_fdt_addr;
+
+	return 0;
+}
-- 
2.48.1

Re: [PATCH v2 1/4] riscv: lib: Add a default implementation of board_fdt_blob_setup

[Leo Liang]

On Fri, Mar 07, 2025 at 01:13:41PM +0000, Yao Zi wrote:
> It's common for S-Mode proper U-Boot to retrieve a FDT blob along with
> taking control from SBI firmware. Add a weak version of
> board_fdt_blob_setup to make use of it by default, avoiding copy-pasting
> similar functions among boards.
> 
> Signed-off-by: Yao Zi <ziyao@disroot.org>
> ---
>  arch/riscv/lib/Makefile |  1 +
>  arch/riscv/lib/board.c  | 19 +++++++++++++++++++
>  2 files changed, 20 insertions(+)
>  create mode 100644 arch/riscv/lib/board.c

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

Re: [PATCH v2 1/4] riscv: lib: Add a default implementation of board_fdt_blob_setup

[Leo Liang]

Hi Yao,

On Fri, Mar 07, 2025 at 01:13:41PM +0000, Yao Zi wrote:
> It's common for S-Mode proper U-Boot to retrieve a FDT blob along with
> taking control from SBI firmware. Add a weak version of
> board_fdt_blob_setup to make use of it by default, avoiding copy-pasting
> similar functions among boards.
> 
> Signed-off-by: Yao Zi <ziyao@disroot.org>
> Reviewed-by: Leo Yu-Chi Liang <ycliang@andestech.com>
> ---
>  arch/riscv/lib/Makefile |  1 +
>  arch/riscv/lib/board.c  | 19 +++++++++++++++++++
>  2 files changed, 20 insertions(+)
>  create mode 100644 arch/riscv/lib/board.c
> 
> diff --git a/arch/riscv/lib/Makefile b/arch/riscv/lib/Makefile
> index 268116f3757..b33f9c646dd 100644
> --- a/arch/riscv/lib/Makefile
> +++ b/arch/riscv/lib/Makefile
> @@ -27,6 +27,7 @@ obj-$(CONFIG_$(XPL_)SMP) += smp.o
>  obj-$(CONFIG_XPL_BUILD)	+= spl.o
>  obj-y   += fdt_fixup.o
>  obj-$(CONFIG_$(SPL)CMD_BDI) += bdinfo.o
> +obj-$(CONFIG_OF_BOARD) += board.o
>  
>  # For building EFI apps
>  CFLAGS_NON_EFI := -fstack-protector-strong
> diff --git a/arch/riscv/lib/board.c b/arch/riscv/lib/board.c
> new file mode 100644
> index 00000000000..1630355b2b1
> --- /dev/null
> +++ b/arch/riscv/lib/board.c
> @@ -0,0 +1,19 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * RISC-V-specific handling of firmware FDT
> + */
> +
> +#include <asm/global_data.h>
> +#include <linux/errno.h>
> +
> +DECLARE_GLOBAL_DATA_PTR;
> +
> +__weak int board_fdt_blob_setup(void **fdtp)
> +{
> +	if (IS_ENABLED(CONFIG_XPL_BUILD) || !gd->arch.firmware_fdt_addr)
> +		return -EEXIST;

We don't need this check "CONFIG_XPL_BUILD", do we?
We do need this setup function for SPL and adding this would fail CI test.

> +
> +	*fdtp = (void *)gd->arch.firmware_fdt_addr;

We should add proper casting to suppress compile warning for 32 bit.

Best regards,
Leo
> +
> +	return 0;
> +}

Re: [PATCH v2 1/4] riscv: lib: Add a default implementation of board_fdt_blob_setup

[Leo Liang]

Hi Yao,

On Fri, Mar 07, 2025 at 01:13:41PM +0000, Yao Zi wrote:
> It's common for S-Mode proper U-Boot to retrieve a FDT blob along with
> taking control from SBI firmware. Add a weak version of
> board_fdt_blob_setup to make use of it by default, avoiding copy-pasting
> similar functions among boards.
> 
> Signed-off-by: Yao Zi <ziyao@disroot.org>
> Reviewed-by: Leo Yu-Chi Liang <ycliang@andestech.com>
> ---
>  arch/riscv/lib/Makefile |  1 +
>  arch/riscv/lib/board.c  | 19 +++++++++++++++++++
>  2 files changed, 20 insertions(+)
>  create mode 100644 arch/riscv/lib/board.c
> 
> diff --git a/arch/riscv/lib/Makefile b/arch/riscv/lib/Makefile
> index 268116f3757..b33f9c646dd 100644
> --- a/arch/riscv/lib/Makefile
> +++ b/arch/riscv/lib/Makefile
> @@ -27,6 +27,7 @@ obj-$(CONFIG_$(XPL_)SMP) += smp.o
>  obj-$(CONFIG_XPL_BUILD)	+= spl.o
>  obj-y   += fdt_fixup.o
>  obj-$(CONFIG_$(SPL)CMD_BDI) += bdinfo.o
> +obj-$(CONFIG_OF_BOARD) += board.o
>  
>  # For building EFI apps
>  CFLAGS_NON_EFI := -fstack-protector-strong
> diff --git a/arch/riscv/lib/board.c b/arch/riscv/lib/board.c
> new file mode 100644
> index 00000000000..1630355b2b1
> --- /dev/null
> +++ b/arch/riscv/lib/board.c
> @@ -0,0 +1,19 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * RISC-V-specific handling of firmware FDT
> + */
> +
> +#include <asm/global_data.h>
> +#include <linux/errno.h>
> +
> +DECLARE_GLOBAL_DATA_PTR;
> +
> +__weak int board_fdt_blob_setup(void **fdtp)
> +{
> +	if (IS_ENABLED(CONFIG_XPL_BUILD) || !gd->arch.firmware_fdt_addr)
> +		return -EEXIST;
> +
> +	*fdtp = (void *)gd->arch.firmware_fdt_addr;

I could fix the 'CONFIG_XPL_BUILD' check and add casting when merging.
Thanks for the patch!

Best regards,
Leo
> +
> +	return 0;
> +}

[PATCH v2 2/4] board: qemu: riscv: Remove duplicated board_fdt_blob_setup

[Yao Zi]

The default version should work for RISC-V QEMU.

Signed-off-by: Yao Zi <ziyao@disroot.org>
Reviewed-by: Leo Yu-Chi Liang <ycliang@andestech.com>
---
 board/emulation/qemu-riscv/qemu-riscv.c | 8 --------
 1 file changed, 8 deletions(-)

diff --git a/board/emulation/qemu-riscv/qemu-riscv.c b/board/emulation/qemu-riscv/qemu-riscv.c
index a90222ea6a4..70190ebe8fc 100644
--- a/board/emulation/qemu-riscv/qemu-riscv.c
+++ b/board/emulation/qemu-riscv/qemu-riscv.c
@@ -63,11 +63,3 @@ int board_fit_config_name_match(const char *name)
 	return 0;
 }
 #endif
-
-int board_fdt_blob_setup(void **fdtp)
-{
-	/* Stored the DTB address there during our init */
-	*fdtp = (void *)(ulong)gd->arch.firmware_fdt_addr;
-
-	return 0;
-}
-- 
2.48.1

[PATCH v2 3/4] board: starfive: Remove duplicated board_fdt_blob_setup

[Yao Zi]

The default version should work for Starfive VisionFive 2.

Signed-off-by: Yao Zi <ziyao@disroot.org>
Reviewed-by: Leo Yu-Chi Liang <ycliang@andestech.com>
---
 board/starfive/visionfive2/starfive_visionfive2.c | 10 ----------
 1 file changed, 10 deletions(-)

diff --git a/board/starfive/visionfive2/starfive_visionfive2.c b/board/starfive/visionfive2/starfive_visionfive2.c
index 3940d45b13f..96fb8dfe934 100644
--- a/board/starfive/visionfive2/starfive_visionfive2.c
+++ b/board/starfive/visionfive2/starfive_visionfive2.c
@@ -115,16 +115,6 @@ int board_late_init(void)
 	return 0;
 }
 
-int board_fdt_blob_setup(void **fdtp)
-{
-	if (gd->arch.firmware_fdt_addr) {
-		*fdtp = (ulong *)(uintptr_t)gd->arch.firmware_fdt_addr;
-		return 0;
-	}
-
-	return -EEXIST;
-}
-
 int ft_board_setup(void *blob, struct bd_info *bd)
 {
 	return fdt_fixup_memory(blob, 0x40000000, gd->ram_size);
-- 
2.48.1

[PATCH v2 4/4] board: sifive: Remove dead board_fdt_blob_setup

[Yao Zi]

CONFIG_OF_BOARD isn't enabled on SiFive Unleashed and Unmatched, thus
board_fdt_blob_setup is actually dead code on these platforms. Let's
remove it.

Signed-off-by: Yao Zi <ziyao@disroot.org>
Reviewed-by: Leo Yu-Chi Liang <ycliang@andestech.com>
---
 board/sifive/unleashed/unleashed.c | 11 -----------
 board/sifive/unmatched/unmatched.c | 10 ----------
 2 files changed, 21 deletions(-)

diff --git a/board/sifive/unleashed/unleashed.c b/board/sifive/unleashed/unleashed.c
index c1c374610c3..f5da289b836 100644
--- a/board/sifive/unleashed/unleashed.c
+++ b/board/sifive/unleashed/unleashed.c
@@ -114,17 +114,6 @@ int misc_init_r(void)
 
 #endif
 
-int board_fdt_blob_setup(void **fdtp)
-{
-	if (gd->arch.firmware_fdt_addr) {
-		*fdtp = (ulong *)(uintptr_t)gd->arch.firmware_fdt_addr;
-
-		return 0;
-	}
-
-	return -EEXIST;
-}
-
 int board_init(void)
 {
 	/* enable all cache ways */
diff --git a/board/sifive/unmatched/unmatched.c b/board/sifive/unmatched/unmatched.c
index 23e03e145ee..a57ce1f10fe 100644
--- a/board/sifive/unmatched/unmatched.c
+++ b/board/sifive/unmatched/unmatched.c
@@ -10,16 +10,6 @@
 #include <dm.h>
 #include <asm/sections.h>
 
-int board_fdt_blob_setup(void **fdtp)
-{
-	if (gd->arch.firmware_fdt_addr) {
-		*fdtp = (ulong *)(uintptr_t)gd->arch.firmware_fdt_addr;
-		return 0;
-	}
-
-	return -EEXIST;
-}
-
 int board_init(void)
 {
 	/* enable all cache ways */
-- 
2.48.1