[RFC PATCH 0/2] sh: Add Casio fx-9750GIII board support

[RFC PATCH 0/2] sh: Add Casio fx-9750GIII board support

[Artem Novak]

Add initial board support for the Casio fx-9750GIII graphing calculator,
based on the Renesas SH7305 (SH4A) processor.

The series introduces the board Device Tree 
and minimal SuperH machine registration.

The Casio board Device Tree binding
has been submitted separately.

This RFC depends on SH7305 CPU and SoC support,
which is not yet available upstream.

The board Device Tree passes dtbs_check, and the machine vector compiles using
Casio GCC 14.3.0. The two patches also apply cleanly to Linux v7.3-rc2.
Hardware boot testing with an unmodified upstream kernel has not yet been
accomplished.

I need comments, they are obviously welcome.

Artem Novak (2):
  sh: dts: add Casio fx-9750GIII board
  sh: fx9750giii: add board support

 arch/sh/Makefile                        |  1 +
 arch/sh/boards/Kconfig                  | 12 ++++++++++++
 arch/sh/boards/Makefile                 |  1 +
 arch/sh/boards/mach-fx9750giii/Makefile |  2 ++
 arch/sh/boards/mach-fx9750giii/setup.c  | 14 ++++++++++++++
 arch/sh/boot/dts/Makefile               |  1 +
 arch/sh/boot/dts/fx9750giii.dts         | 15 +++++++++++++++
 7 files changed, 46 insertions(+)
 create mode 100644 arch/sh/boards/mach-fx9750giii/Makefile
 create mode 100644 arch/sh/boards/mach-fx9750giii/setup.c
 create mode 100644 arch/sh/boot/dts/fx9750giii.dts

-- 
2.56.0

[RFC PATCH 1/2] sh: dts: add Casio fx-9750GIII board

[Artem Novak]

Describe the Casio fx-9750GIII graphing calculator, which uses the Renesas SH7305 processor.

Added the board Device Tree and its DTB build rule.
The description uses existing SH7305 SoC include
and affirm the calculator memory region.

Signed-off-by: Artem Novak <artem122novak@gmail.com>
---
 arch/sh/boot/dts/Makefile       |  1 +
 arch/sh/boot/dts/fx9750giii.dts | 15 +++++++++++++++
 2 files changed, 16 insertions(+)
 create mode 100644 arch/sh/boot/dts/fx9750giii.dts

diff --git a/arch/sh/boot/dts/Makefile b/arch/sh/boot/dts/Makefile
index d109978a5eb9..4887fb16dbf2 100644
--- a/arch/sh/boot/dts/Makefile
+++ b/arch/sh/boot/dts/Makefile
@@ -1,2 +1,3 @@
 # SPDX-License-Identifier: GPL-2.0-only
+dtb-$(CONFIG_SH_FX9750GIII) += fx9750giii.dtb
 obj-$(CONFIG_BUILTIN_DTB) += $(addsuffix .dtb.o, $(CONFIG_BUILTIN_DTB_NAME))
diff --git a/arch/sh/boot/dts/fx9750giii.dts b/arch/sh/boot/dts/fx9750giii.dts
new file mode 100644
index 000000000000..bccae22e4899
--- /dev/null
+++ b/arch/sh/boot/dts/fx9750giii.dts
@@ -0,0 +1,15 @@
+// SPDX-License-Identifier: GPL-2.0-only
+// Copyright (C) 2026 Artem Novak
+/dts-v1/;
+
+#include "sh7305.dtsi"
+
+/ {
+	model = "Casio fx-9750GIII";
+	compatible = "casio,fx-9750giii", "renesas,sh7305";
+
+	memory@8000000 {
+		device_type = "memory";
+		reg = <0x08000000 0x00080000>;
+	};
+};
-- 
2.56.0

[RFC PATCH 2/2] sh: fx9750giii: add board support

[Artem Novak]

Add minimal machine support for the Casio fx-9750GIII graphing calculator.

Introducing a board Kconfig option and registration on its machine vector.
Wire the board directory into the SuperH build system.

Signed-off-by: Artem Novak <artem122novak@gmail.com>
---
 arch/sh/Makefile                        |  1 +
 arch/sh/boards/Kconfig                  | 12 ++++++++++++
 arch/sh/boards/Makefile                 |  1 +
 arch/sh/boards/mach-fx9750giii/Makefile |  2 ++
 arch/sh/boards/mach-fx9750giii/setup.c  | 14 ++++++++++++++
 5 files changed, 30 insertions(+)
 create mode 100644 arch/sh/boards/mach-fx9750giii/Makefile
 create mode 100644 arch/sh/boards/mach-fx9750giii/setup.c

diff --git a/arch/sh/Makefile b/arch/sh/Makefile
index 380e3b7dc597..28b431a8c8d9 100644
--- a/arch/sh/Makefile
+++ b/arch/sh/Makefile
@@ -128,6 +128,7 @@ machdir-$(CONFIG_SH_KFR2R09)			+= mach-kfr2r09
 machdir-$(CONFIG_SH_ECOVEC)			+= mach-ecovec24
 machdir-$(CONFIG_SH_SDK7786)			+= mach-sdk7786
 machdir-$(CONFIG_SH_X3PROTO)			+= mach-x3proto
+machdir-$(CONFIG_SH_FX9750GIII)		+= mach-fx9750giii
 machdir-$(CONFIG_SH_LANDISK)			+= mach-landisk
 machdir-y					+= mach-common
 
diff --git a/arch/sh/boards/Kconfig b/arch/sh/boards/Kconfig
index d89b74177233..f1571b0e5f1f 100644
--- a/arch/sh/boards/Kconfig
+++ b/arch/sh/boards/Kconfig
@@ -326,6 +326,18 @@ config SH_LBOX_RE2
 	help
 	  Select L-BOX RE2 if configuring for the NTT COMWARE L-BOX RE2.
 
+
+config SH_FX9750GIII
+	bool "Casio fx-9750GIII"
+	depends on CPU_SUBTYPE_SH7305
+	select OF
+	select OF_EARLY_FLATTREE
+	help
+	  Enable board support for the Casio fx-9750GIII
+	  graphing calculator, based on the Renesas SH7305.
+	  This selects the calculator machine vector and
+	  enables early Device Tree support for the board.
+
 config SH_X3PROTO
 	bool "SH-X3 Prototype board"
 	depends on CPU_SUBTYPE_SHX3
diff --git a/arch/sh/boards/Makefile b/arch/sh/boards/Makefile
index fbbc350ca854..c60d038872e9 100644
--- a/arch/sh/boards/Makefile
+++ b/arch/sh/boards/Makefile
@@ -32,6 +32,7 @@ obj-$(CONFIG_SH_ECOVEC)		+= mach-ecovec24/
 obj-$(CONFIG_SH_SDK7780)	+= mach-sdk7780/
 obj-$(CONFIG_SH_SDK7786)	+= mach-sdk7786/
 obj-$(CONFIG_SH_X3PROTO)	+= mach-x3proto/
+obj-$(CONFIG_SH_FX9750GIII)	+= mach-fx9750giii/
 obj-$(CONFIG_SH_SH7763RDP)	+= mach-sh7763rdp/
 obj-$(CONFIG_SH_LANDISK)	+= mach-landisk/
 obj-$(CONFIG_SH_LBOX_RE2)	+= mach-lboxre2/
diff --git a/arch/sh/boards/mach-fx9750giii/Makefile b/arch/sh/boards/mach-fx9750giii/Makefile
new file mode 100644
index 000000000000..0d6df7044567
--- /dev/null
+++ b/arch/sh/boards/mach-fx9750giii/Makefile
@@ -0,0 +1,2 @@
+# SPDX-License-Identifier: GPL-2.0
+obj-y += setup.o
diff --git a/arch/sh/boards/mach-fx9750giii/setup.c b/arch/sh/boards/mach-fx9750giii/setup.c
new file mode 100644
index 000000000000..233decdd1bfe
--- /dev/null
+++ b/arch/sh/boards/mach-fx9750giii/setup.c
@@ -0,0 +1,14 @@
+// SPDX-License-Identifier: GPL-2.0-only
+// Copyright (C) 2026 Artem Novak
+/*
+ * Casio fx-9750GIII platform support
+ *
+ */
+
+#include <linux/init.h>
+
+#include <asm/machvec.h>
+
+static struct sh_machine_vector mv_fx9750giii __initmv = {
+	.mv_name	= "Casio fx-9750GIII",
+};
-- 
2.56.0

Re: [RFC PATCH 1/2] sh: dts: add Casio fx-9750GIII board

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 3 potential issue(s) to consider:
- [High] sh: dts: missing sh7305.dtsi include breaks fx9750giii.dtb build
- [Medium] sh: dts: fx9750giii uses unselectable Kconfig and missing sh7305.dtsi
- [Low] sh: dts: undocumented compatible strings and vendor prefix in fx9750giii.dts
--

commit 82402ca3074df3c76845795376be9cd0891cff1d
Author: Artem Novak <artem122novak@gmail.com>

sh: dts: add Casio fx-9750GIII board

This commit adds the device tree source file fx9750giii.dts for the Casio
fx-9750GIII graphing calculator and registers fx9750giii.dtb in
arch/sh/boot/dts/Makefile.

> diff --git a/arch/sh/boot/dts/Makefile b/arch/sh/boot/dts/Makefile
> index d109978a5eb9c..4887fb16dbf23 100644
> --- a/arch/sh/boot/dts/Makefile
> +++ b/arch/sh/boot/dts/Makefile
> @@ -1,2 +1,3 @@
>  # SPDX-License-Identifier: GPL-2.0-only
> +dtb-$(CONFIG_SH_FX9750GIII) += fx9750giii.dtb

[Severity: Medium]
Can CONFIG_SH_FX9750GIII ever be enabled to build fx9750giii.dtb?

In arch/sh/boot/dts/Makefile, dtb-$(CONFIG_SH_FX9750GIII) references
CONFIG_SH_FX9750GIII, which is not defined in this patch. Although the
follow-up commit ("sh: fx9750giii: add board support") adds config
SH_FX9750GIII in arch/sh/boards/Kconfig, it specifies:

    depends on CPU_SUBTYPE_SH7305

which is not defined anywhere in arch/sh/Kconfig or the kernel tree.

Because CONFIG_SH_FX9750GIII remains unselectable, fx9750giii.dtb is only
placed in $(dtb-), where scripts/Makefile.dtbs promotes it into $(dtb-y) when
CONFIG_OF_ALL_DTBS=y is enabled:

    dtb-$(CONFIG_OF_ALL_DTBS) += $(dtb-)

At that point, cmd_dtc in scripts/Makefile.dtbs attempts to preprocess
arch/sh/boot/dts/fx9750giii.dts and fails because sh7305.dtsi is missing.

>  obj-$(CONFIG_BUILTIN_DTB) += $(addsuffix .dtb.o, $(CONFIG_BUILTIN_DTB_NAME))
> diff --git a/arch/sh/boot/dts/fx9750giii.dts b/arch/sh/boot/dts/fx9750giii.dts
> new file mode 100644
> index 0000000000000..bccae22e48994
> --- /dev/null
> +++ b/arch/sh/boot/dts/fx9750giii.dts
> @@ -0,0 +1,15 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +// Copyright (C) 2026 Artem Novak
> +/dts-v1/;
> +
> +#include "sh7305.dtsi"

[Severity: High]
Where is sh7305.dtsi defined in the kernel tree?

The commit message states "The description uses existing SH7305 SoC include",
and arch/sh/boot/dts/fx9750giii.dts includes sh7305.dtsi, but no sh7305.dtsi
file exists in arch/sh/boot/dts/, scripts/dtc/include-prefixes/, or anywhere
else in the repository (nor is it added in the follow-up commit
"sh: fx9750giii: add board support"). Without it, the board device tree also
lacks the SoC definitions (cpu nodes, interrupt controller, timers, clocks,
and root #address-cells and #size-cells).

When building fx9750giii.dtb directly, setting
CONFIG_BUILTIN_DTB_NAME="fx9750giii", or building under CONFIG_OF_ALL_DTBS=y
(where scripts/Makefile.dtbs promotes $(dtb-) into $(dtb-y)), cmd_dtc in
scripts/Makefile.dtbs runs:

    $(HOSTCC) -E $(dtc_cpp_flags) -x assembler-with-cpp -o $(dtc-tmp) $< ; \

Doesn't this cause a build regression when the preprocessor fails with
"sh7305.dtsi: No such file or directory"?

> +
> +/ {
> +	model = "Casio fx-9750GIII";
> +	compatible = "casio,fx-9750giii", "renesas,sh7305";

[Severity: Low]
Should the vendor prefix and compatible strings in the root node "/" of
arch/sh/boot/dts/fx9750giii.dts be documented in the device tree bindings
first?

The vendor prefix "casio" is not listed in
Documentation/devicetree/bindings/vendor-prefixes.yaml, and neither
"casio,fx-9750giii" nor "renesas,sh7305" is documented under
Documentation/devicetree/bindings/ (such as
Documentation/devicetree/bindings/soc/renesas/renesas.yaml), which causes
scripts/checkpatch.pl and dtbs_check warnings when validating fx9750giii.dts.

[ ... ]

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20261022063936.472520-1-artem122novak@gmail.com?part=1

Re: [RFC PATCH 2/2] sh: fx9750giii: add board support

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 4 potential issue(s) to consider:
- [High] sh: fx9750giii: missing DT memory and init callbacks in mv_fx9750giii
- [Medium] sh: SH_FX9750GIII depends on non-existent symbol CPU_SUBTYPE_SH7305
- [Medium] sh: fx9750giii: missing CPU_SUBTYPE_SH7305 Kconfig and sh7305.dtsi
- [Low] sh: Makefile: machdir-y adds non-existent arch/sh/include/mach-fx9750giii
--

commit c63ad0601911097299cc121ef0d798a2a17535ce
Author: Artem Novak <artem122novak@gmail.com>

sh: fx9750giii: add board support

This commit adds minimal machine support and a Kconfig option for the Casio
fx-9750GIII graphing calculator. It registers the board machine vector and
wires the board directory into the SuperH build system.

> diff --git a/arch/sh/Makefile b/arch/sh/Makefile
> index 7b420424b6d7c..324c7e080eea6 100644
> --- a/arch/sh/Makefile
> +++ b/arch/sh/Makefile
> @@ -123,6 +123,7 @@ machdir-$(CONFIG_SH_KFR2R09)			+= mach-kfr2r09
>  machdir-$(CONFIG_SH_ECOVEC)			+= mach-ecovec24
>  machdir-$(CONFIG_SH_SDK7786)			+= mach-sdk7786
>  machdir-$(CONFIG_SH_X3PROTO)			+= mach-x3proto
> +machdir-$(CONFIG_SH_FX9750GIII)		+= mach-fx9750giii

[Severity: Low]
Should mach-fx9750giii be added to machdir-y here when
arch/sh/include/mach-fx9750giii does not exist?

In arch/sh/Makefile, machdir-y is used to construct compiler header search
paths:

    KBUILD_CPPFLAGS += $(addprefix -I $(srctree)/arch/sh/include/, $(cpuincdir-y) $(machdir-y))

while board directory compilation is handled by obj-$(CONFIG_SH_FX9750GIII)
in arch/sh/boards/Makefile.

When building the kernel with CONFIG_SH_FX9750GIII=y, this passes
-I $(srctree)/arch/sh/include/mach-fx9750giii for a directory that does not
exist, triggering -Wmissing-include-dirs warnings under W=1 (and build
failures with CONFIG_WERROR=y or in subdirectories that enable
-Wmissing-include-dirs). Other boards without board-specific headers under
arch/sh/include/, such as mach-rsk and mach-lboxre2, only add themselves to
arch/sh/boards/Makefile.

[ ... ]

> diff --git a/arch/sh/boards/Kconfig b/arch/sh/boards/Kconfig
> index d89b741772337..f1571b0e5f1f9 100644
> --- a/arch/sh/boards/Kconfig
> +++ b/arch/sh/boards/Kconfig
> @@ -326,6 +326,18 @@ config SH_LBOX_RE2
>  	help
>  	  Select L-BOX RE2 if configuring for the NTT COMWARE L-BOX RE2.
>  
> +
> +config SH_FX9750GIII
> +	bool "Casio fx-9750GIII"
> +	depends on CPU_SUBTYPE_SH7305

[Severity: Medium]
Can CONFIG_SH_FX9750GIII ever be enabled when CPU_SUBTYPE_SH7305 is not
defined in Kconfig?

In arch/sh/boards/Kconfig, config SH_FX9750GIII depends on
CPU_SUBTYPE_SH7305, which is not defined in arch/sh/Kconfig alongside other
processor subtypes (such as config CPU_SUBTYPE_SH7343) or anywhere else in
the kernel tree:

    # SH4AL-DSP Processor Support

    config CPU_SUBTYPE_SH7343
            bool "Support SH7343 processor"

Because Kconfig evaluates undefined symbols as n, this dependency is never
satisfied when configuring the kernel for arch/sh, leaving
CONFIG_SH_FX9750GIII and arch/sh/boards/mach-fx9750giii/ unreachable and
unbuildable.

> +	select OF
> +	select OF_EARLY_FLATTREE
> +	help
> +	  Enable board support for the Casio fx-9750GIII
> +	  graphing calculator, based on the Renesas SH7305.
> +	  This selects the calculator machine vector and
> +	  enables early Device Tree support for the board.

[Severity: Medium]
Is this series also missing sh7305.dtsi in addition to the
CPU_SUBTYPE_SH7305 Kconfig definition?

In the subsequent commit in this series ("sh: dts: add Casio fx-9750GIII
board"), arch/sh/boot/dts/Makefile registers:

    dtb-$(CONFIG_SH_FX9750GIII) += fx9750giii.dtb

and arch/sh/boot/dts/fx9750giii.dts contains:

    #include "sh7305.dtsi"

However, sh7305.dtsi does not exist anywhere in the kernel tree. When
building dtbs with CONFIG_OF_ALL_DTBS=y or building fx9750giii.dtb directly
(or if CONFIG_SH_FX9750GIII is enabled), preprocessing
arch/sh/boot/dts/fx9750giii.dts fails because sh7305.dtsi is missing.

[ ... ]

> diff --git a/arch/sh/boards/mach-fx9750giii/setup.c b/arch/sh/boards/mach-fx9750giii/setup.c
> new file mode 100644
> index 0000000000000..233decdd1bfef
> --- /dev/null
> +++ b/arch/sh/boards/mach-fx9750giii/setup.c
> @@ -0,0 +1,14 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +// Copyright (C) 2026 Artem Novak
> +/*
> + * Casio fx-9750GIII platform support
> + *
> + */
> +
> +#include <linux/init.h>
> +
> +#include <asm/machvec.h>
> +
> +static struct sh_machine_vector mv_fx9750giii __initmv = {
> +	.mv_name	= "Casio fx-9750GIII",
> +};

[Severity: High]
Will leaving .mv_mem_init, .mv_mem_reserve, .mv_init_irq, and .mv_clk_init
unset in mv_fx9750giii corrupt the device tree and memory layout during
early boot?

During early boot on this platform, _stext calls sh_fdt_init() ->
early_init_dt_scan() -> early_init_dt_scan_memory(), which registers the
512 KB device tree memory region at 0x08000000 via memblock_add().

However, in arch/sh/boards/mach-fx9750giii/setup.c, mv_fx9750giii only sets
.mv_name and leaves .mv_mem_init, .mv_mem_reserve, .mv_init_irq, and
.mv_clk_init as NULL.

When setup_arch() -> sh_mv_setup() runs in arch/sh/kernel/machvec.c, a NULL
.mv_mem_init is replaced with generic_mem_init():

    mv_set(irq_demux);
    mv_set(mode_pins);
    mv_set(mem_init);

Then setup_arch() -> paging_init() in arch/sh/mm/init.c invokes
sh_mv.mv_mem_init() and checks sh_mv.mv_mem_reserve:

    sh_mv.mv_mem_init();

    early_reserve_mem();

    /*
     * Once the early reservations are out of the way, give the
     * platforms a chance to kick out some memory.
     */
    if (sh_mv.mv_mem_reserve)
            sh_mv.mv_mem_reserve();

In arch/sh/mm/init.c, generic_mem_init() unconditionally adds
__MEMORY_SIZE (64 MB by default via CONFIG_MEMORY_SIZE) on top of the
512 KB device tree memory node:

    void __init generic_mem_init(void)
    {
            memblock_add(__MEMORY_START, __MEMORY_SIZE);
    }

Furthermore, because .mv_mem_reserve is NULL, the in-RAM flattened device
tree blob and device tree reserved-memory regions are never reserved in
memblock before setup_arch() calls unflatten_device_tree(), allowing the
page allocator to overwrite live device_node structures. Leaving
.mv_init_irq and .mv_clk_init NULL also skips irqchip_init() and
of_clk_init(NULL) during init_IRQ() and clk_init().

For comparison, sh_of_generic_mv in arch/sh/boards/of-generic.c initializes
these callbacks for device tree platforms:

    static struct sh_machine_vector __initmv sh_of_generic_mv = {
            .mv_setup       = sh_of_setup,
            .mv_name        = "devicetree", /* replaced by DT root's model */
            .mv_irq_demux   = sh_of_irq_demux,
            .mv_init_irq    = sh_of_init_irq,
            .mv_clk_init    = sh_of_clk_init,
            .mv_mode_pins   = noopi,
            .mv_mem_init    = noop,
            .mv_mem_reserve = sh_of_mem_reserve,
    };

Should mv_fx9750giii wire up these device tree callbacks (or use the
generic device tree machine vector)?

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20261022063936.472520-1-artem122novak@gmail.com?part=2