kbuild: rust: keep Rust objects out of Clang LTO with inline helpersgrafted

Under `CONFIG_LTO_CLANG` + `CONFIG_RUST_INLINE_HELPERS`, one may hit
`objtool` errors such as:

    vmlinux.o: error: objtool: _R..._3Gsp4boot+0xd6a:
    can't find jump dest instruction at .text._R..._3Gsp4boot+0x1dfd

The reason is that in such builds, the Clang invocation that compiles
the combined Rust plus helpers bitcode emits LLVM bitcode (again) --
the final code generation happens in the linker's LTO step, which the
`-mllvm` trap options passed to Clang do not reach.

This, in turn, means that unreachable traps are missing, and the
impossible paths do not merely fallthrough to the next symbol, but past
the end of their own section, since LTO builds place each function in
its own section.

Thus filter `CC_FLAGS_LTO` out of the Clang invocation, so that it always
emits machine code directly, with the traps in place.

Assisted-by: LLM
Cc: Gary Guo <gary@garyguo.net>
Cc: Boqun Feng <boqun@kernel.org>
Cc: Alice Ryhl <aliceryhl@google.com>
Cc: Matthew Maurer <mmaurer@google.com>
Cc: Josh Poimboeuf <jpoimboe@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: stable@vger.kernel.org
Fixes: 3a2486cc1da5 ("kbuild: rust: provide an option to inline C helpers into Rust")
Acked-by: Gary Guo <gary@garyguo.net>
Link: https://patch.msgid.link/20260816133233.197500-2-ojeda@kernel.org
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

3 files changed, 190 insertions, 0 deletions

diff --git a/drivers/phy/sophgo/Kconfig b/drivers/phy/sophgo/Kconfig
new file mode 100644
index 000000000..2c943bbe1
--- /dev/null
+++ b/drivers/phy/sophgo/Kconfig
@@ -0,0 +1,19 @@
+# SPDX-License-Identifier: GPL-2.0-only
+#
+# Phy drivers for Sophgo platforms
+#
+
+if ARCH_SOPHGO || COMPILE_TEST
+
+config PHY_SOPHGO_CV1800_USB2
+	tristate "Sophgo CV18XX/SG200X USB 2.0 PHY support"
+	depends on MFD_SYSCON
+	depends on USB_SUPPORT
+	select GENERIC_PHY
+	help
+	  Enable this to support the USB 2.0 PHY used with
+	  the DWC2 USB controller in Sophgo CV18XX/SG200X
+	  series SoC.
+	  If unsure, say N.
+
+endif # ARCH_SOPHGO || COMPILE_TEST
diff --git a/drivers/phy/sophgo/Makefile b/drivers/phy/sophgo/Makefile
new file mode 100644
index 000000000..318060661
--- /dev/null
+++ b/drivers/phy/sophgo/Makefile
@@ -0,0 +1,2 @@
+# SPDX-License-Identifier: GPL-2.0
+obj-$(CONFIG_PHY_SOPHGO_CV1800_USB2)	+= phy-cv1800-usb2.o
diff --git a/drivers/phy/sophgo/phy-cv1800-usb2.c b/drivers/phy/sophgo/phy-cv1800-usb2.c
new file mode 100644
index 000000000..6fe846534
--- /dev/null
+++ b/drivers/phy/sophgo/phy-cv1800-usb2.c
@@ -0,0 +1,169 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2025 Inochi Amaoto <inochiama@outlook.com>
+ */
+
+#include <linux/clk.h>
+#include <linux/bitfield.h>
+#include <linux/debugfs.h>
+#include <linux/kernel.h>
+#include <linux/mfd/syscon.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_address.h>
+#include <linux/platform_device.h>
+#include <linux/phy/phy.h>
+#include <linux/regmap.h>
+#include <linux/spinlock.h>
+
+#define REG_USB_PHY_CTRL		0x048
+
+#define PHY_VBUS_POWER_EN		BIT(0)
+#define PHY_VBUS_POWER			BIT(1)
+#define PHY_ID_OVERWRITE_EN		BIT(6)
+#define PHY_ID_OVERWRITE_MODE		BIT(7)
+#define PHY_ID_OVERWRITE_MODE_HOST	FIELD_PREP(BIT(7), 0)
+#define PHY_ID_OVERWRITE_MODE_DEVICE	FIELD_PREP(BIT(7), 1)
+
+#define PHY_APP_CLK_RATE		125000000
+#define PHY_LPM_CLK_RATE		12000000
+#define PHY_STB_CLK_RATE		333334
+
+struct cv1800_usb_phy {
+	struct phy	*phy;
+	struct regmap	*syscon;
+	spinlock_t	lock;
+	struct clk	*usb_app_clk;
+	struct clk	*usb_lpm_clk;
+	struct clk	*usb_stb_clk;
+	bool		support_otg;
+};
+
+static int cv1800_usb_phy_set_mode(struct phy *_phy,
+				   enum phy_mode mode, int submode)
+{
+	struct cv1800_usb_phy *phy = phy_get_drvdata(_phy);
+	unsigned int regval = 0;
+	int ret;
+
+	dev_info(&phy->phy->dev, "set mode %d", (int)mode);
+
+	switch (mode) {
+	case PHY_MODE_USB_DEVICE:
+		regval = PHY_ID_OVERWRITE_EN | PHY_ID_OVERWRITE_MODE_DEVICE;
+		regmap_clear_bits(phy->syscon, REG_USB_PHY_CTRL, PHY_VBUS_POWER);
+		break;
+	case PHY_MODE_USB_HOST:
+		regval = PHY_ID_OVERWRITE_EN | PHY_ID_OVERWRITE_MODE_HOST;
+		regmap_set_bits(phy->syscon, REG_USB_PHY_CTRL, PHY_VBUS_POWER);
+		break;
+	case PHY_MODE_USB_OTG:
+		if (!phy->support_otg)
+			return 0;
+
+		ret = regmap_read(phy->syscon, REG_USB_PHY_CTRL, &regval);
+		if (ret)
+			return ret;
+
+		regval = FIELD_GET(PHY_ID_OVERWRITE_MODE, regval);
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	return regmap_update_bits(phy->syscon, REG_USB_PHY_CTRL,
+				  PHY_ID_OVERWRITE_EN | PHY_ID_OVERWRITE_MODE,
+				  regval);
+}
+
+static int cv1800_usb_phy_set_clock(struct cv1800_usb_phy *phy)
+{
+	int ret;
+
+	ret = clk_set_rate(phy->usb_app_clk, PHY_APP_CLK_RATE);
+	if (ret)
+		return ret;
+
+	ret = clk_set_rate(phy->usb_lpm_clk, PHY_LPM_CLK_RATE);
+	if (ret)
+		return ret;
+
+	return clk_set_rate(phy->usb_stb_clk, PHY_STB_CLK_RATE);
+}
+
+static const struct phy_ops cv1800_usb_phy_ops = {
+	.set_mode	= cv1800_usb_phy_set_mode,
+	.owner		= THIS_MODULE,
+};
+
+static int cv1800_usb_phy_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct device *parent = dev->parent;
+	struct cv1800_usb_phy *phy;
+	struct phy_provider *phy_provider;
+	int ret;
+
+	if (!parent)
+		return -ENODEV;
+
+	phy = devm_kmalloc(dev, sizeof(*phy), GFP_KERNEL);
+	if (!phy)
+		return -ENOMEM;
+
+	phy->syscon = syscon_node_to_regmap(parent->of_node);
+	if (IS_ERR_OR_NULL(phy->syscon))
+		return -ENODEV;
+
+	phy->support_otg = false;
+
+	spin_lock_init(&phy->lock);
+
+	phy->usb_app_clk = devm_clk_get_enabled(dev, "app");
+	if (IS_ERR(phy->usb_app_clk))
+		return dev_err_probe(dev, PTR_ERR(phy->usb_app_clk),
+			"Failed to get app clock\n");
+
+	phy->usb_lpm_clk = devm_clk_get_enabled(dev, "lpm");
+	if (IS_ERR(phy->usb_lpm_clk))
+		return dev_err_probe(dev, PTR_ERR(phy->usb_lpm_clk),
+			"Failed to get lpm clock\n");
+
+	phy->usb_stb_clk = devm_clk_get_enabled(dev, "stb");
+	if (IS_ERR(phy->usb_stb_clk))
+		return dev_err_probe(dev, PTR_ERR(phy->usb_stb_clk),
+			"Failed to get stb clock\n");
+
+	phy->phy = devm_phy_create(dev, NULL, &cv1800_usb_phy_ops);
+	if (IS_ERR(phy->phy))
+		return dev_err_probe(dev, PTR_ERR(phy->phy),
+			"Failed to create phy\n");
+
+	ret = cv1800_usb_phy_set_clock(phy);
+	if (ret)
+		return ret;
+
+	phy_set_drvdata(phy->phy, phy);
+	phy_provider = devm_of_phy_provider_register(dev, of_phy_simple_xlate);
+
+	return PTR_ERR_OR_ZERO(phy_provider);
+}
+
+static const struct of_device_id cv1800_usb_phy_ids[] = {
+	{ .compatible = "sophgo,cv1800b-usb2-phy" },
+	{ },
+};
+MODULE_DEVICE_TABLE(of, cv1800_usb_phy_ids);
+
+static struct platform_driver cv1800_usb_phy_driver = {
+	.probe = cv1800_usb_phy_probe,
+	.driver = {
+		.name = "cv1800-usb2-phy",
+		.of_match_table = cv1800_usb_phy_ids,
+	 },
+};
+module_platform_driver(cv1800_usb_phy_driver);
+
+MODULE_AUTHOR("Inochi Amaoto <inochiama@outlook.com>");
+MODULE_DESCRIPTION("CV1800/SG2000 SoC USB 2.0 PHY driver");
+MODULE_LICENSE("GPL");