[PATCH v2 0/3] ARM: vt8500: Add runtime SoC version identification

[PATCH v2 0/3] ARM: vt8500: Add runtime SoC version identification

[Alexey Charkov]

VIA/WonderMedia SoCs have a chip ID register, which is helpful for
selecting support for correct sets of hardware quirks at runtime, add
code for it.

This will enable the use of SOC bus match tables in individual drivers,
allowing for finer grained feature selection where device trees might
not provide full information about what the hardware expects (such as
with non-user-visible SoC revisions having different behavior within
the same user-visible SoC version).

This series intentionally omits the updates to MAINTAINERS, as there
are multiple VT8500 related submissions this cycle which may go via
different trees (and cause pain in sequencing the merges). It will be
updated separately in a single pass to cover everything VT8500 related.

Signed-off-by: Alexey Charkov <alchark@gmail.com>
---
Changes in v2:
- Moved the DT binding under hwinfo directory
- Changed the compatible string to be based on SoC version
- Reworked the driver into a platform one, and switched to devm_ functions
  (all of the above - thanks Krzysztof)
- Link to v1: https://lore.kernel.org/r/20250423-wmt-soc-driver-v1-0-bd8bf32521c2@gmail.com

---
Alexey Charkov (3):
      dt-bindings: soc: Add VIA/WonderMedia SoC identification
      soc: Add VIA/WonderMedia SoC identification driver
      ARM: dts: vt8500: add DT nodes for the system config ID register

 .../bindings/hwinfo/via,vt8500-scc-id.yaml         |  37 ++++++
 arch/arm/boot/dts/vt8500/vt8500.dtsi               |   5 +
 arch/arm/boot/dts/vt8500/wm8505.dtsi               |   5 +
 arch/arm/boot/dts/vt8500/wm8650.dtsi               |   5 +
 arch/arm/boot/dts/vt8500/wm8750.dtsi               |   5 +
 arch/arm/boot/dts/vt8500/wm8850.dtsi               |   5 +
 drivers/soc/Kconfig                                |   1 +
 drivers/soc/Makefile                               |   1 +
 drivers/soc/vt8500/Kconfig                         |  20 ++++
 drivers/soc/vt8500/Makefile                        |   2 +
 drivers/soc/vt8500/wmt-socinfo.c                   | 125 +++++++++++++++++++++
 11 files changed, 211 insertions(+)
---
base-commit: 37ff6e9a2ce321b7932d3987701757fb4d87b0e6
change-id: 20250423-wmt-soc-driver-de26d67bd4ef

Best regards,
-- 
Alexey Charkov <alchark@gmail.com>

[PATCH v2 1/3] dt-bindings: soc: Add VIA/WonderMedia SoC identification

[Alexey Charkov]

VIA/WonderMedia SoC's have a chip ID register inside their system
configuration controller space, which can be used to identify
appropriate hardware quirks at runtime. Add binding for it.

Signed-off-by: Alexey Charkov <alchark@gmail.com>
---
 .../bindings/hwinfo/via,vt8500-scc-id.yaml         | 37 ++++++++++++++++++++++
 1 file changed, 37 insertions(+)

diff --git a/Documentation/devicetree/bindings/hwinfo/via,vt8500-scc-id.yaml b/Documentation/devicetree/bindings/hwinfo/via,vt8500-scc-id.yaml
new file mode 100644
index 0000000000000000000000000000000000000000..87bdb947dedb47b508528d70543aba067aa03e95
--- /dev/null
+++ b/Documentation/devicetree/bindings/hwinfo/via,vt8500-scc-id.yaml
@@ -0,0 +1,37 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/soc/vt8500/via,vt8500-scc-id.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: VIA/WonderMedia SoC system configuration information
+
+maintainers:
+  - Alexey Charkov <alchark@gmail.com>
+
+description:
+  The system configuration controller on VIA/WonderMedia SoC's contains a chip
+  identifier and revision used to differentiate between different hardware
+  versions of on-chip IP blocks having their own peculiarities which may or
+  may not be captured by their respective DT compatible strings
+
+properties:
+  compatible:
+    items:
+      - const: via,vt8500-scc-id
+
+  reg:
+    maxItems: 1
+
+required:
+  - compatible
+  - reg
+
+additionalProperties: false
+
+examples:
+  - |
+    chipid@d8120000 {
+        compatible = "via,vt8500-scc-id";
+        reg = <0xd8120000 0x4>;
+    };

-- 
2.49.0

[PATCH v2 2/3] soc: Add VIA/WonderMedia SoC identification driver

[Alexey Charkov]

Add a small SOC bus driver to parse the chip ID and revision made
available on VIA/WonderMedia SoCs via their system configuration
controller's SCC_ID register.

This is intended to select appropriate sets of on-chip device quirks
at runtime, as it has been found that even within the same SoC
version there can be register-incompatible differences, such as
with the SDMMC controller on WM8505 rev. A0-A1 vs. rev. A2.

The list of SoC versions is compiled from various vendor source dumps
and not all of them have corresponding mainline driver support.
Some of them also have been seen with varying on-chip markings while
sharing the same hardware chip ID's (as is the case with e.g. WM8850
vs. WM8950). In such cases the selection of names to use here among
those seen in various source dumps and chip markings was arbitrary.

Suggested by Krzysztof at [1] - thanks a lot!

[1] https://lore.kernel.org/all/14de236b-e2a7-4bde-986d-1e5ffddd01b4@kernel.org/

Signed-off-by: Alexey Charkov <alchark@gmail.com>
---
 drivers/soc/Kconfig              |   1 +
 drivers/soc/Makefile             |   1 +
 drivers/soc/vt8500/Kconfig       |  20 +++++++
 drivers/soc/vt8500/Makefile      |   2 +
 drivers/soc/vt8500/wmt-socinfo.c | 125 +++++++++++++++++++++++++++++++++++++++
 5 files changed, 149 insertions(+)

diff --git a/drivers/soc/Kconfig b/drivers/soc/Kconfig
index 6a8daeb8c4b96cd29d56343b338a423140b89896..37ca3f094f8994c7e9c7c99c3ba47d168d41ce30 100644
--- a/drivers/soc/Kconfig
+++ b/drivers/soc/Kconfig
@@ -28,6 +28,7 @@ source "drivers/soc/tegra/Kconfig"
 source "drivers/soc/ti/Kconfig"
 source "drivers/soc/ux500/Kconfig"
 source "drivers/soc/versatile/Kconfig"
+source "drivers/soc/vt8500/Kconfig"
 source "drivers/soc/xilinx/Kconfig"
 
 endmenu
diff --git a/drivers/soc/Makefile b/drivers/soc/Makefile
index 2037a8695cb2898659a434803dcdfa2d95b1dbd6..777255401252eab554f56bded7ff8ea5611704bf 100644
--- a/drivers/soc/Makefile
+++ b/drivers/soc/Makefile
@@ -34,4 +34,5 @@ obj-$(CONFIG_ARCH_TEGRA)	+= tegra/
 obj-y				+= ti/
 obj-$(CONFIG_ARCH_U8500)	+= ux500/
 obj-y				+= versatile/
+obj-y				+= vt8500/
 obj-y				+= xilinx/
diff --git a/drivers/soc/vt8500/Kconfig b/drivers/soc/vt8500/Kconfig
new file mode 100644
index 0000000000000000000000000000000000000000..2b2350678c3f70297c51f94eb77674c01be773d8
--- /dev/null
+++ b/drivers/soc/vt8500/Kconfig
@@ -0,0 +1,20 @@
+# SPDX-License-Identifier: GPL-2.0-only
+
+if ARCH_VT8500 || COMPILE_TEST
+
+menu "VIA/WonderMedia SoC drivers"
+
+config WMT_SOCINFO
+	bool "VIA/WonderMedia SoC Information driver"
+	default ARCH_VT8500
+	select SOC_BUS
+	default ARCH_VT8500
+	help
+	  Say yes to support decoding of VIA/WonderMedia system configuration
+	  register information. This currently includes just the chip ID register
+	  which helps identify the exact hardware revision of the SoC the kernel
+	  is running on (to know if any revision-specific quirks are required)
+
+endmenu
+
+endif
diff --git a/drivers/soc/vt8500/Makefile b/drivers/soc/vt8500/Makefile
new file mode 100644
index 0000000000000000000000000000000000000000..05964c5f2890989c1d794af4f5af10f849a497bc
--- /dev/null
+++ b/drivers/soc/vt8500/Makefile
@@ -0,0 +1,2 @@
+# SPDX-License-Identifier: GPL-2.0-only
+obj-$(CONFIG_WMT_SOCINFO)	+= wmt-socinfo.o
diff --git a/drivers/soc/vt8500/wmt-socinfo.c b/drivers/soc/vt8500/wmt-socinfo.c
new file mode 100644
index 0000000000000000000000000000000000000000..461f8c1ae56ee367dc2c84a58ff8fada0dfdaed0
--- /dev/null
+++ b/drivers/soc/vt8500/wmt-socinfo.c
@@ -0,0 +1,125 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright 2025 Alexey Charkov <alchark@gmail.com>
+ * Based on aspeed-socinfo.c
+ */
+
+#include <linux/dev_printk.h>
+#include <linux/device.h>
+#include <linux/io.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/sys_soc.h>
+
+static const struct {
+	const char *name;
+	const u32 id;
+} chip_id_table[] = {
+	/* VIA */
+	{ "VT8420", 0x3300 },
+	{ "VT8430", 0x3357 },
+	{ "VT8500", 0x3400 },
+
+	/* WonderMedia */
+	{ "WM8425", 0x3429 },
+	{ "WM8435", 0x3437 },
+	{ "WM8440", 0x3451 },
+	{ "WM8505", 0x3426 },
+	{ "WM8650", 0x3465 },
+	{ "WM8750", 0x3445 },
+	{ "WM8850", 0x3481 },
+	{ "WM8880", 0x3498 },
+};
+
+static const char *sccid_to_name(u32 sccid)
+{
+	u32 id = sccid >> 16;
+	unsigned int i;
+
+	for (i = 0 ; i < ARRAY_SIZE(chip_id_table) ; ++i) {
+		if (chip_id_table[i].id == id)
+			return chip_id_table[i].name;
+	}
+
+	return "Unknown";
+}
+
+static int wmt_socinfo_probe(struct platform_device *pdev)
+{
+	struct device_node *np = pdev->dev.of_node;
+	struct soc_device_attribute *attrs;
+	struct soc_device *soc_dev;
+	char letter, digit;
+	void __iomem *reg;
+	u32 sccid;
+
+	reg = devm_of_iomap(&pdev->dev, np, 0, NULL);
+	if (IS_ERR(reg))
+		return PTR_ERR(reg);
+
+	sccid = readl(reg);
+
+	attrs = devm_kzalloc(&pdev->dev, sizeof(*attrs), GFP_KERNEL);
+	if (!attrs)
+		return -ENOMEM;
+
+	/*
+	 * Machine: VIA APC Rock
+	 * Family: WM8850
+	 * Revision: A2
+	 * SoC ID: raw silicon revision id (34810103 in hexadecimal)
+	 */
+
+	attrs->family = sccid_to_name(sccid);
+
+	letter = (sccid >> 8) & 0xf;
+	letter = (letter - 1) + 'A';
+	digit = sccid & 0xff;
+	digit = (digit - 1) + '0';
+	attrs->revision = devm_kasprintf(&pdev->dev, GFP_KERNEL,
+					 "%c%c", letter, digit);
+
+	attrs->soc_id = devm_kasprintf(&pdev->dev, GFP_KERNEL, "%08x", sccid);
+
+	if (!attrs->revision || !attrs->soc_id)
+		return -ENOMEM;
+
+	soc_dev = soc_device_register(attrs);
+	if (IS_ERR(soc_dev))
+		return PTR_ERR(soc_dev);
+
+	dev_info(&pdev->dev,
+		 "VIA/WonderMedia %s rev %s (%s)\n",
+		 attrs->family,
+		 attrs->revision,
+		 attrs->soc_id);
+
+	platform_set_drvdata(pdev, soc_dev);
+	return 0;
+}
+
+static void wmt_socinfo_remove(struct platform_device *pdev)
+{
+	struct soc_device *soc_dev = platform_get_drvdata(pdev);
+
+	soc_device_unregister(soc_dev);
+}
+
+static const struct of_device_id wmt_socinfo_ids[] = {
+	{ .compatible = "via,vt8500-scc-id" },
+	{ /* Sentinel */ },
+};
+
+static struct platform_driver wmt_socinfo = {
+	.probe = wmt_socinfo_probe,
+	.remove = wmt_socinfo_remove,
+	.driver = {
+		.name = "wmt-socinfo",
+		.of_match_table = wmt_socinfo_ids,
+	},
+};
+module_platform_driver(wmt_socinfo);
+
+MODULE_AUTHOR("Alexey Charkov <alchark@gmail.com>");
+MODULE_DESCRIPTION("VIA/WonderMedia socinfo driver");
+MODULE_LICENSE("GPL");

-- 
2.49.0

[PATCH v2 3/3] ARM: dts: vt8500: add DT nodes for the system config ID register

[Alexey Charkov]

Every VIA/WonderMedia SoC has a 32-bit chip ID register at the
MMIO address 0xd8120000. Add respective device tree nodes to let
the system code access it at runtime for the selection of appropriate
hardware quirks where needed.

Signed-off-by: Alexey Charkov <alchark@gmail.com>
---
 arch/arm/boot/dts/vt8500/vt8500.dtsi | 5 +++++
 arch/arm/boot/dts/vt8500/wm8505.dtsi | 5 +++++
 arch/arm/boot/dts/vt8500/wm8650.dtsi | 5 +++++
 arch/arm/boot/dts/vt8500/wm8750.dtsi | 5 +++++
 arch/arm/boot/dts/vt8500/wm8850.dtsi | 5 +++++
 5 files changed, 25 insertions(+)

diff --git a/arch/arm/boot/dts/vt8500/vt8500.dtsi b/arch/arm/boot/dts/vt8500/vt8500.dtsi
index 09f5ed3e6821b72fc440f9de3df0ad484d2c4e17..2ba021585d4889f29777a12473964c29f999f3a0 100644
--- a/arch/arm/boot/dts/vt8500/vt8500.dtsi
+++ b/arch/arm/boot/dts/vt8500/vt8500.dtsi
@@ -55,6 +55,11 @@ pinctrl: pinctrl@d8110000 {
 			#gpio-cells = <2>;
 		};
 
+		chipid@d8120000 {
+			compatible = "via,vt8500-scc-id";
+			reg = <0xd8120000 0x4>;
+		};
+
 		pmc@d8130000 {
 			compatible = "via,vt8500-pmc";
 			reg = <0xd8130000 0x1000>;
diff --git a/arch/arm/boot/dts/vt8500/wm8505.dtsi b/arch/arm/boot/dts/vt8500/wm8505.dtsi
index c81810b967bb349419a5ac7db4e788faec3695fb..99c064c916b2279797f71261ca9306e9dcd4bbd8 100644
--- a/arch/arm/boot/dts/vt8500/wm8505.dtsi
+++ b/arch/arm/boot/dts/vt8500/wm8505.dtsi
@@ -66,6 +66,11 @@ pinctrl: pinctrl@d8110000 {
 			#gpio-cells = <2>;
 		};
 
+		chipid@d8120000 {
+			compatible = "via,vt8500-scc-id";
+			reg = <0xd8120000 0x4>;
+		};
+
 		pmc@d8130000 {
 			compatible = "via,vt8500-pmc";
 			reg = <0xd8130000 0x1000>;
diff --git a/arch/arm/boot/dts/vt8500/wm8650.dtsi b/arch/arm/boot/dts/vt8500/wm8650.dtsi
index 555008120a3e315591d2ca49a39d354925d570fd..0d6c7bd87f7dcce0eef056d04c38ab1de5d52639 100644
--- a/arch/arm/boot/dts/vt8500/wm8650.dtsi
+++ b/arch/arm/boot/dts/vt8500/wm8650.dtsi
@@ -62,6 +62,11 @@ pinctrl: pinctrl@d8110000 {
 			#gpio-cells = <2>;
 		};
 
+		chipid@d8120000 {
+			compatible = "via,vt8500-scc-id";
+			reg = <0xd8120000 0x4>;
+		};
+
 		pmc@d8130000 {
 			compatible = "via,vt8500-pmc";
 			reg = <0xd8130000 0x1000>;
diff --git a/arch/arm/boot/dts/vt8500/wm8750.dtsi b/arch/arm/boot/dts/vt8500/wm8750.dtsi
index 309f6e5129fb817d343cd58a8d90340afd8d6eb9..0158c0ba5dd110957eac38775d3bf3ebd2ab4154 100644
--- a/arch/arm/boot/dts/vt8500/wm8750.dtsi
+++ b/arch/arm/boot/dts/vt8500/wm8750.dtsi
@@ -68,6 +68,11 @@ pinctrl: pinctrl@d8110000 {
 			#gpio-cells = <2>;
 		};
 
+		chipid@d8120000 {
+			compatible = "via,vt8500-scc-id";
+			reg = <0xd8120000 0x4>;
+		};
+
 		pmc@d8130000 {
 			compatible = "via,vt8500-pmc";
 			reg = <0xd8130000 0x1000>;
diff --git a/arch/arm/boot/dts/vt8500/wm8850.dtsi b/arch/arm/boot/dts/vt8500/wm8850.dtsi
index 3f4a514d65e2ac7658b73cc9c4f3cae1407265bc..c4bfb4d30aad0358b39cbf30edf0c63e32167bbd 100644
--- a/arch/arm/boot/dts/vt8500/wm8850.dtsi
+++ b/arch/arm/boot/dts/vt8500/wm8850.dtsi
@@ -65,6 +65,11 @@ pinctrl: pinctrl@d8110000 {
 			#gpio-cells = <2>;
 		};
 
+		chipid@d8120000 {
+			compatible = "via,vt8500-scc-id";
+			reg = <0xd8120000 0x4>;
+		};
+
 		pmc@d8130000 {
 			compatible = "via,vt8500-pmc";
 			reg = <0xd8130000 0x1000>;

-- 
2.49.0

Re: [PATCH v2 1/3] dt-bindings: soc: Add VIA/WonderMedia SoC identification

[Rob Herring (Arm)]

On Sat, 03 May 2025 02:04:23 +0400, Alexey Charkov wrote:
> VIA/WonderMedia SoC's have a chip ID register inside their system
> configuration controller space, which can be used to identify
> appropriate hardware quirks at runtime. Add binding for it.
> 
> Signed-off-by: Alexey Charkov <alchark@gmail.com>
> ---
>  .../bindings/hwinfo/via,vt8500-scc-id.yaml         | 37 ++++++++++++++++++++++
>  1 file changed, 37 insertions(+)
> 

My bot found errors running 'make dt_binding_check' on your patch:

yamllint warnings/errors:

dtschema/dtc warnings/errors:
/builds/robherring/dt-review-ci/linux/Documentation/devicetree/bindings/hwinfo/via,vt8500-scc-id.yaml: $id: Cannot determine base path from $id, relative path/filename doesn't match actual path or filename
 	 $id: http://devicetree.org/schemas/soc/vt8500/via,vt8500-scc-id.yaml
 	file: /builds/robherring/dt-review-ci/linux/Documentation/devicetree/bindings/hwinfo/via,vt8500-scc-id.yaml

doc reference errors (make refcheckdocs):

See https://patchwork.ozlabs.org/project/devicetree-bindings/patch/20250503-wmt-soc-driver-v2-1-8c774ad84d47@gmail.com

The base for the series is generally the latest rc1. A different dependency
should be noted in *this* patch.

If you already ran 'make dt_binding_check' and didn't see the above
error(s), then make sure 'yamllint' is installed and dt-schema is up to
date:

pip3 install dtschema --upgrade

Please check and re-submit after running the above command yourself. Note
that DT_SCHEMA_FILES can be set to your schema file to speed up checking
your schema. However, it must be unset to test all examples with your schema.