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>

1 files changed, 338 insertions, 0 deletions

diff --git a/drivers/phy/broadcom/phy-bcm-sr-usb.c b/drivers/phy/broadcom/phy-bcm-sr-usb.c
new file mode 100644
index 000000000..6bcfe8360
--- /dev/null
+++ b/drivers/phy/broadcom/phy-bcm-sr-usb.c
@@ -0,0 +1,338 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2016-2018 Broadcom
+ */
+
+#include <linux/delay.h>
+#include <linux/io.h>
+#include <linux/iopoll.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/phy/phy.h>
+#include <linux/platform_device.h>
+
+enum bcm_usb_phy_version {
+	BCM_SR_USB_COMBO_PHY,
+	BCM_SR_USB_HS_PHY,
+};
+
+enum bcm_usb_phy_reg {
+	PLL_CTRL,
+	PHY_CTRL,
+	PHY_PLL_CTRL,
+};
+
+/* USB PHY registers */
+
+static const u8 bcm_usb_combo_phy_ss[] = {
+	[PLL_CTRL]		= 0x18,
+	[PHY_CTRL]		= 0x14,
+};
+
+static const u8 bcm_usb_combo_phy_hs[] = {
+	[PLL_CTRL]	= 0x0c,
+	[PHY_CTRL]	= 0x10,
+};
+
+static const u8 bcm_usb_hs_phy[] = {
+	[PLL_CTRL]	= 0x8,
+	[PHY_CTRL]	= 0xc,
+};
+
+enum pll_ctrl_bits {
+	PLL_RESETB,
+	SSPLL_SUSPEND_EN,
+	PLL_SEQ_START,
+	PLL_LOCK,
+};
+
+static const u8 u3pll_ctrl[] = {
+	[PLL_RESETB]		= 0,
+	[SSPLL_SUSPEND_EN]	= 1,
+	[PLL_SEQ_START]		= 2,
+	[PLL_LOCK]		= 3,
+};
+
+#define HSPLL_PDIV_MASK		0xF
+#define HSPLL_PDIV_VAL		0x1
+
+static const u8 u2pll_ctrl[] = {
+	[PLL_RESETB]	= 5,
+	[PLL_LOCK]	= 6,
+};
+
+enum bcm_usb_phy_ctrl_bits {
+	CORERDY,
+	PHY_RESETB,
+	PHY_PCTL,
+};
+
+#define PHY_PCTL_MASK	0xffff
+#define SSPHY_PCTL_VAL	0x0006
+
+static const u8 u3phy_ctrl[] = {
+	[PHY_RESETB]	= 1,
+	[PHY_PCTL]	= 2,
+};
+
+static const u8 u2phy_ctrl[] = {
+	[CORERDY]		= 0,
+	[PHY_RESETB]		= 5,
+	[PHY_PCTL]		= 6,
+};
+
+struct bcm_usb_phy_cfg {
+	uint32_t type;
+	uint32_t version;
+	void __iomem *regs;
+	struct phy *phy;
+	const u8 *offset;
+};
+
+#define PLL_LOCK_RETRY_COUNT	1000
+
+enum bcm_usb_phy_type {
+	USB_HS_PHY,
+	USB_SS_PHY,
+};
+
+#define NUM_BCM_SR_USB_COMBO_PHYS	2
+
+static inline void bcm_usb_reg32_clrbits(void __iomem *addr, uint32_t clear)
+{
+	writel(readl(addr) & ~clear, addr);
+}
+
+static inline void bcm_usb_reg32_setbits(void __iomem *addr, uint32_t set)
+{
+	writel(readl(addr) | set, addr);
+}
+
+static int bcm_usb_pll_lock_check(void __iomem *addr, u32 bit)
+{
+	u32 data;
+	int ret;
+
+	ret = readl_poll_timeout_atomic(addr, data, (data & bit), 1,
+					PLL_LOCK_RETRY_COUNT);
+	if (ret)
+		pr_err("%s: FAIL\n", __func__);
+
+	return ret;
+}
+
+static int bcm_usb_ss_phy_init(struct bcm_usb_phy_cfg *phy_cfg)
+{
+	int ret = 0;
+	void __iomem *regs = phy_cfg->regs;
+	const u8 *offset;
+	u32 rd_data;
+
+	offset = phy_cfg->offset;
+
+	/* Set pctl with mode and soft reset */
+	rd_data = readl(regs + offset[PHY_CTRL]);
+	rd_data &= ~(PHY_PCTL_MASK << u3phy_ctrl[PHY_PCTL]);
+	rd_data |= (SSPHY_PCTL_VAL << u3phy_ctrl[PHY_PCTL]);
+	writel(rd_data, regs + offset[PHY_CTRL]);
+
+	bcm_usb_reg32_clrbits(regs + offset[PLL_CTRL],
+			      BIT(u3pll_ctrl[SSPLL_SUSPEND_EN]));
+	bcm_usb_reg32_setbits(regs + offset[PLL_CTRL],
+			      BIT(u3pll_ctrl[PLL_SEQ_START]));
+	bcm_usb_reg32_setbits(regs + offset[PLL_CTRL],
+			      BIT(u3pll_ctrl[PLL_RESETB]));
+
+	/* Maximum timeout for PLL reset done */
+	msleep(30);
+
+	ret = bcm_usb_pll_lock_check(regs + offset[PLL_CTRL],
+				     BIT(u3pll_ctrl[PLL_LOCK]));
+
+	return ret;
+}
+
+static int bcm_usb_hs_phy_init(struct bcm_usb_phy_cfg *phy_cfg)
+{
+	int ret = 0;
+	void __iomem *regs = phy_cfg->regs;
+	const u8 *offset;
+
+	offset = phy_cfg->offset;
+
+	bcm_usb_reg32_clrbits(regs + offset[PLL_CTRL],
+			      BIT(u2pll_ctrl[PLL_RESETB]));
+	bcm_usb_reg32_setbits(regs + offset[PLL_CTRL],
+			      BIT(u2pll_ctrl[PLL_RESETB]));
+
+	ret = bcm_usb_pll_lock_check(regs + offset[PLL_CTRL],
+				     BIT(u2pll_ctrl[PLL_LOCK]));
+
+	return ret;
+}
+
+static int bcm_usb_phy_reset(struct phy *phy)
+{
+	struct bcm_usb_phy_cfg *phy_cfg = phy_get_drvdata(phy);
+	void __iomem *regs = phy_cfg->regs;
+	const u8 *offset;
+
+	offset = phy_cfg->offset;
+
+	if (phy_cfg->type == USB_HS_PHY) {
+		bcm_usb_reg32_clrbits(regs + offset[PHY_CTRL],
+				      BIT(u2phy_ctrl[CORERDY]));
+		bcm_usb_reg32_setbits(regs + offset[PHY_CTRL],
+				      BIT(u2phy_ctrl[CORERDY]));
+	}
+
+	return 0;
+}
+
+static int bcm_usb_phy_init(struct phy *phy)
+{
+	struct bcm_usb_phy_cfg *phy_cfg = phy_get_drvdata(phy);
+	int ret = -EINVAL;
+
+	if (phy_cfg->type == USB_SS_PHY)
+		ret = bcm_usb_ss_phy_init(phy_cfg);
+	else if (phy_cfg->type == USB_HS_PHY)
+		ret = bcm_usb_hs_phy_init(phy_cfg);
+
+	return ret;
+}
+
+static const struct phy_ops sr_phy_ops = {
+	.init		= bcm_usb_phy_init,
+	.reset		= bcm_usb_phy_reset,
+	.owner		= THIS_MODULE,
+};
+
+static struct phy *bcm_usb_phy_xlate(struct device *dev,
+				     const struct of_phandle_args *args)
+{
+	struct bcm_usb_phy_cfg *phy_cfg;
+	int phy_idx;
+
+	phy_cfg = dev_get_drvdata(dev);
+	if (!phy_cfg)
+		return ERR_PTR(-EINVAL);
+
+	if (phy_cfg->version == BCM_SR_USB_COMBO_PHY) {
+		phy_idx = args->args[0];
+
+		if (WARN_ON(phy_idx > 1))
+			return ERR_PTR(-ENODEV);
+
+		return phy_cfg[phy_idx].phy;
+	} else
+		return phy_cfg->phy;
+}
+
+static int bcm_usb_phy_create(struct device *dev, struct device_node *node,
+			      void __iomem *regs, uint32_t version)
+{
+	struct bcm_usb_phy_cfg *phy_cfg;
+	int idx;
+
+	if (version == BCM_SR_USB_COMBO_PHY) {
+		phy_cfg = devm_kzalloc(dev, NUM_BCM_SR_USB_COMBO_PHYS *
+				       sizeof(struct bcm_usb_phy_cfg),
+				       GFP_KERNEL);
+		if (!phy_cfg)
+			return -ENOMEM;
+
+		for (idx = 0; idx < NUM_BCM_SR_USB_COMBO_PHYS; idx++) {
+			phy_cfg[idx].regs = regs;
+			phy_cfg[idx].version = version;
+			if (idx == 0) {
+				phy_cfg[idx].offset = bcm_usb_combo_phy_hs;
+				phy_cfg[idx].type = USB_HS_PHY;
+			} else {
+				phy_cfg[idx].offset = bcm_usb_combo_phy_ss;
+				phy_cfg[idx].type = USB_SS_PHY;
+			}
+			phy_cfg[idx].phy = devm_phy_create(dev, node,
+							   &sr_phy_ops);
+			if (IS_ERR(phy_cfg[idx].phy))
+				return PTR_ERR(phy_cfg[idx].phy);
+
+			phy_set_drvdata(phy_cfg[idx].phy, &phy_cfg[idx]);
+		}
+	} else if (version == BCM_SR_USB_HS_PHY) {
+		phy_cfg = devm_kzalloc(dev, sizeof(struct bcm_usb_phy_cfg),
+				       GFP_KERNEL);
+		if (!phy_cfg)
+			return -ENOMEM;
+
+		phy_cfg->regs = regs;
+		phy_cfg->version = version;
+		phy_cfg->offset = bcm_usb_hs_phy;
+		phy_cfg->type = USB_HS_PHY;
+		phy_cfg->phy = devm_phy_create(dev, node, &sr_phy_ops);
+		if (IS_ERR(phy_cfg->phy))
+			return PTR_ERR(phy_cfg->phy);
+
+		phy_set_drvdata(phy_cfg->phy, phy_cfg);
+	} else
+		return -ENODEV;
+
+	dev_set_drvdata(dev, phy_cfg);
+
+	return 0;
+}
+
+static const struct of_device_id bcm_usb_phy_of_match[] = {
+	{
+		.compatible = "brcm,sr-usb-combo-phy",
+		.data = (void *)BCM_SR_USB_COMBO_PHY,
+	},
+	{
+		.compatible = "brcm,sr-usb-hs-phy",
+		.data = (void *)BCM_SR_USB_HS_PHY,
+	},
+	{ /* sentinel */ },
+};
+MODULE_DEVICE_TABLE(of, bcm_usb_phy_of_match);
+
+static int bcm_usb_phy_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct device_node *dn = dev->of_node;
+	const struct of_device_id *of_id;
+	void __iomem *regs;
+	int ret;
+	enum bcm_usb_phy_version version;
+	struct phy_provider *phy_provider;
+
+	regs = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(regs))
+		return PTR_ERR(regs);
+
+	of_id = of_match_node(bcm_usb_phy_of_match, dn);
+	if (of_id)
+		version = (uintptr_t)of_id->data;
+	else
+		return -ENODEV;
+
+	ret = bcm_usb_phy_create(dev, dn, regs, version);
+	if (ret)
+		return ret;
+
+	phy_provider = devm_of_phy_provider_register(dev, bcm_usb_phy_xlate);
+
+	return PTR_ERR_OR_ZERO(phy_provider);
+}
+
+static struct platform_driver bcm_usb_phy_driver = {
+	.driver = {
+		.name = "phy-bcm-sr-usb",
+		.of_match_table = bcm_usb_phy_of_match,
+	},
+	.probe = bcm_usb_phy_probe,
+};
+module_platform_driver(bcm_usb_phy_driver);
+
+MODULE_AUTHOR("Broadcom");
+MODULE_DESCRIPTION("Broadcom stingray USB Phy driver");
+MODULE_LICENSE("GPL v2");