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, 433 insertions, 0 deletions

diff --git a/drivers/extcon/extcon-palmas.c b/drivers/extcon/extcon-palmas.c
new file mode 100644
index 000000000..d339b8680
--- /dev/null
+++ b/drivers/extcon/extcon-palmas.c
@@ -0,0 +1,433 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Palmas USB transceiver driver
+ *
+ * Copyright (C) 2013 Texas Instruments Incorporated - https://www.ti.com
+ * Author: Graeme Gregory <gg@slimlogic.co.uk>
+ * Author: Kishon Vijay Abraham I <kishon@ti.com>
+ * Based on twl6030_usb.c
+ * Author: Hema HK <hemahk@ti.com>
+ */
+
+#include <linux/devm-helpers.h>
+#include <linux/module.h>
+#include <linux/interrupt.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+#include <linux/err.h>
+#include <linux/mfd/palmas.h>
+#include <linux/of.h>
+#include <linux/of_platform.h>
+#include <linux/gpio/consumer.h>
+#include <linux/workqueue.h>
+
+#define USB_GPIO_DEBOUNCE_MS	20	/* ms */
+
+static const unsigned int palmas_extcon_cable[] = {
+	EXTCON_USB,
+	EXTCON_USB_HOST,
+	EXTCON_NONE,
+};
+
+static void palmas_usb_wakeup(struct palmas *palmas, int enable)
+{
+	if (enable)
+		palmas_write(palmas, PALMAS_USB_OTG_BASE, PALMAS_USB_WAKEUP,
+			PALMAS_USB_WAKEUP_ID_WK_UP_COMP);
+	else
+		palmas_write(palmas, PALMAS_USB_OTG_BASE, PALMAS_USB_WAKEUP, 0);
+}
+
+static irqreturn_t palmas_vbus_irq_handler(int irq, void *_palmas_usb)
+{
+	struct palmas_usb *palmas_usb = _palmas_usb;
+	struct extcon_dev *edev = palmas_usb->edev;
+	unsigned int vbus_line_state;
+
+	palmas_read(palmas_usb->palmas, PALMAS_INTERRUPT_BASE,
+		PALMAS_INT3_LINE_STATE, &vbus_line_state);
+
+	if (vbus_line_state & PALMAS_INT3_LINE_STATE_VBUS) {
+		if (palmas_usb->linkstat != PALMAS_USB_STATE_VBUS) {
+			palmas_usb->linkstat = PALMAS_USB_STATE_VBUS;
+			extcon_set_state_sync(edev, EXTCON_USB, true);
+			dev_dbg(palmas_usb->dev, "USB cable is attached\n");
+		} else {
+			dev_dbg(palmas_usb->dev,
+				"Spurious connect event detected\n");
+		}
+	} else if (!(vbus_line_state & PALMAS_INT3_LINE_STATE_VBUS)) {
+		if (palmas_usb->linkstat == PALMAS_USB_STATE_VBUS) {
+			palmas_usb->linkstat = PALMAS_USB_STATE_DISCONNECT;
+			extcon_set_state_sync(edev, EXTCON_USB, false);
+			dev_dbg(palmas_usb->dev, "USB cable is detached\n");
+		} else {
+			dev_dbg(palmas_usb->dev,
+				"Spurious disconnect event detected\n");
+		}
+	}
+
+	return IRQ_HANDLED;
+}
+
+static irqreturn_t palmas_id_irq_handler(int irq, void *_palmas_usb)
+{
+	unsigned int set, id_src;
+	struct palmas_usb *palmas_usb = _palmas_usb;
+	struct extcon_dev *edev = palmas_usb->edev;
+
+	palmas_read(palmas_usb->palmas, PALMAS_USB_OTG_BASE,
+		PALMAS_USB_ID_INT_LATCH_SET, &set);
+	palmas_read(palmas_usb->palmas, PALMAS_USB_OTG_BASE,
+		PALMAS_USB_ID_INT_SRC, &id_src);
+
+	if ((set & PALMAS_USB_ID_INT_SRC_ID_GND) &&
+				(id_src & PALMAS_USB_ID_INT_SRC_ID_GND)) {
+		palmas_write(palmas_usb->palmas, PALMAS_USB_OTG_BASE,
+			PALMAS_USB_ID_INT_LATCH_CLR,
+			PALMAS_USB_ID_INT_EN_HI_CLR_ID_GND);
+		palmas_usb->linkstat = PALMAS_USB_STATE_ID;
+		extcon_set_state_sync(edev, EXTCON_USB_HOST, true);
+		dev_dbg(palmas_usb->dev, "USB-HOST cable is attached\n");
+	} else if ((set & PALMAS_USB_ID_INT_SRC_ID_FLOAT) &&
+				(id_src & PALMAS_USB_ID_INT_SRC_ID_FLOAT)) {
+		palmas_write(palmas_usb->palmas, PALMAS_USB_OTG_BASE,
+			PALMAS_USB_ID_INT_LATCH_CLR,
+			PALMAS_USB_ID_INT_EN_HI_CLR_ID_FLOAT);
+		palmas_usb->linkstat = PALMAS_USB_STATE_DISCONNECT;
+		extcon_set_state_sync(edev, EXTCON_USB_HOST, false);
+		dev_dbg(palmas_usb->dev, "USB-HOST cable is detached\n");
+	} else if ((palmas_usb->linkstat == PALMAS_USB_STATE_ID) &&
+				(!(set & PALMAS_USB_ID_INT_SRC_ID_GND))) {
+		palmas_usb->linkstat = PALMAS_USB_STATE_DISCONNECT;
+		extcon_set_state_sync(edev, EXTCON_USB_HOST, false);
+		dev_dbg(palmas_usb->dev, "USB-HOST cable is detached\n");
+	} else if ((palmas_usb->linkstat == PALMAS_USB_STATE_DISCONNECT) &&
+				(id_src & PALMAS_USB_ID_INT_SRC_ID_GND)) {
+		palmas_usb->linkstat = PALMAS_USB_STATE_ID;
+		extcon_set_state_sync(edev, EXTCON_USB_HOST, true);
+		dev_dbg(palmas_usb->dev, "USB-HOST cable is attached\n");
+	}
+
+	return IRQ_HANDLED;
+}
+
+static void palmas_gpio_id_detect(struct work_struct *work)
+{
+	int id;
+	struct palmas_usb *palmas_usb = container_of(to_delayed_work(work),
+						     struct palmas_usb,
+						     wq_detectid);
+	struct extcon_dev *edev = palmas_usb->edev;
+
+	if (!palmas_usb->id_gpiod)
+		return;
+
+	id = gpiod_get_value_cansleep(palmas_usb->id_gpiod);
+
+	if (id) {
+		extcon_set_state_sync(edev, EXTCON_USB_HOST, false);
+		dev_dbg(palmas_usb->dev, "USB-HOST cable is detached\n");
+	} else {
+		extcon_set_state_sync(edev, EXTCON_USB_HOST, true);
+		dev_dbg(palmas_usb->dev, "USB-HOST cable is attached\n");
+	}
+}
+
+static irqreturn_t palmas_gpio_id_irq_handler(int irq, void *_palmas_usb)
+{
+	struct palmas_usb *palmas_usb = _palmas_usb;
+
+	queue_delayed_work(system_power_efficient_wq, &palmas_usb->wq_detectid,
+			   palmas_usb->sw_debounce_jiffies);
+
+	return IRQ_HANDLED;
+}
+
+static void palmas_enable_irq(struct palmas_usb *palmas_usb)
+{
+	palmas_write(palmas_usb->palmas, PALMAS_USB_OTG_BASE,
+		PALMAS_USB_VBUS_CTRL_SET,
+		PALMAS_USB_VBUS_CTRL_SET_VBUS_ACT_COMP);
+
+	if (palmas_usb->enable_id_detection) {
+		palmas_write(palmas_usb->palmas, PALMAS_USB_OTG_BASE,
+			     PALMAS_USB_ID_CTRL_SET,
+			     PALMAS_USB_ID_CTRL_SET_ID_ACT_COMP);
+
+		palmas_write(palmas_usb->palmas, PALMAS_USB_OTG_BASE,
+			     PALMAS_USB_ID_INT_EN_HI_SET,
+			     PALMAS_USB_ID_INT_EN_HI_SET_ID_GND |
+			     PALMAS_USB_ID_INT_EN_HI_SET_ID_FLOAT);
+	}
+
+	if (palmas_usb->enable_vbus_detection)
+		palmas_vbus_irq_handler(palmas_usb->vbus_irq, palmas_usb);
+
+	/* cold plug for host mode needs this delay */
+	if (palmas_usb->enable_id_detection) {
+		msleep(30);
+		palmas_id_irq_handler(palmas_usb->id_irq, palmas_usb);
+	}
+}
+
+static int palmas_usb_probe(struct platform_device *pdev)
+{
+	struct palmas *palmas = dev_get_drvdata(pdev->dev.parent);
+	struct palmas_usb_platform_data	*pdata = dev_get_platdata(&pdev->dev);
+	struct device_node *node = pdev->dev.of_node;
+	struct palmas_usb *palmas_usb;
+	int status;
+
+	if (!palmas) {
+		dev_err(&pdev->dev, "failed to get valid parent\n");
+		return -EINVAL;
+	}
+
+	palmas_usb = devm_kzalloc(&pdev->dev, sizeof(*palmas_usb), GFP_KERNEL);
+	if (!palmas_usb)
+		return -ENOMEM;
+
+	if (node && !pdata) {
+		palmas_usb->wakeup = of_property_read_bool(node, "ti,wakeup");
+		palmas_usb->enable_id_detection = of_property_read_bool(node,
+						"ti,enable-id-detection");
+		palmas_usb->enable_vbus_detection = of_property_read_bool(node,
+						"ti,enable-vbus-detection");
+	} else {
+		palmas_usb->wakeup = true;
+		palmas_usb->enable_id_detection = true;
+		palmas_usb->enable_vbus_detection = true;
+
+		if (pdata)
+			palmas_usb->wakeup = pdata->wakeup;
+	}
+
+	palmas_usb->id_gpiod = devm_gpiod_get_optional(&pdev->dev, "id",
+							GPIOD_IN);
+	if (IS_ERR(palmas_usb->id_gpiod))
+		return dev_err_probe(&pdev->dev, PTR_ERR(palmas_usb->id_gpiod),
+				     "failed to get id gpio\n");
+
+	palmas_usb->vbus_gpiod = devm_gpiod_get_optional(&pdev->dev, "vbus",
+							GPIOD_IN);
+	if (IS_ERR(palmas_usb->vbus_gpiod))
+		return dev_err_probe(&pdev->dev, PTR_ERR(palmas_usb->vbus_gpiod),
+				     "failed to get id gpio\n");
+
+	if (palmas_usb->enable_id_detection && palmas_usb->id_gpiod) {
+		palmas_usb->enable_id_detection = false;
+		palmas_usb->enable_gpio_id_detection = true;
+	}
+
+	if (palmas_usb->enable_vbus_detection && palmas_usb->vbus_gpiod) {
+		palmas_usb->enable_vbus_detection = false;
+		palmas_usb->enable_gpio_vbus_detection = true;
+	}
+
+	if (palmas_usb->enable_gpio_id_detection) {
+		u32 debounce;
+
+		if (of_property_read_u32(node, "debounce-delay-ms", &debounce))
+			debounce = USB_GPIO_DEBOUNCE_MS;
+
+		status = gpiod_set_debounce(palmas_usb->id_gpiod,
+					    debounce * 1000);
+		if (status < 0)
+			palmas_usb->sw_debounce_jiffies = msecs_to_jiffies(debounce);
+	}
+
+	status = devm_delayed_work_autocancel(&pdev->dev,
+					      &palmas_usb->wq_detectid,
+					      palmas_gpio_id_detect);
+	if (status)
+		return status;
+
+	palmas->usb = palmas_usb;
+	palmas_usb->palmas = palmas;
+
+	palmas_usb->dev	 = &pdev->dev;
+
+	palmas_usb_wakeup(palmas, palmas_usb->wakeup);
+
+	platform_set_drvdata(pdev, palmas_usb);
+
+	palmas_usb->edev = devm_extcon_dev_allocate(&pdev->dev,
+						    palmas_extcon_cable);
+	if (IS_ERR(palmas_usb->edev)) {
+		dev_err(&pdev->dev, "failed to allocate extcon device\n");
+		return -ENOMEM;
+	}
+
+	status = devm_extcon_dev_register(&pdev->dev, palmas_usb->edev);
+	if (status) {
+		dev_err(&pdev->dev, "failed to register extcon device\n");
+		return status;
+	}
+
+	if (palmas_usb->enable_id_detection) {
+		palmas_usb->id_otg_irq = regmap_irq_get_virq(palmas->irq_data,
+							     PALMAS_ID_OTG_IRQ);
+		palmas_usb->id_irq = regmap_irq_get_virq(palmas->irq_data,
+							 PALMAS_ID_IRQ);
+		status = devm_request_threaded_irq(palmas_usb->dev,
+				palmas_usb->id_irq,
+				NULL, palmas_id_irq_handler,
+				IRQF_TRIGGER_FALLING | IRQF_TRIGGER_RISING |
+				IRQF_ONESHOT,
+				"palmas_usb_id", palmas_usb);
+		if (status < 0) {
+			dev_err(&pdev->dev, "can't get IRQ %d, err %d\n",
+					palmas_usb->id_irq, status);
+			return status;
+		}
+	} else if (palmas_usb->enable_gpio_id_detection) {
+		palmas_usb->gpio_id_irq = gpiod_to_irq(palmas_usb->id_gpiod);
+		if (palmas_usb->gpio_id_irq < 0) {
+			dev_err(&pdev->dev, "failed to get id irq\n");
+			return palmas_usb->gpio_id_irq;
+		}
+		status = devm_request_threaded_irq(&pdev->dev,
+						   palmas_usb->gpio_id_irq,
+						   NULL,
+						   palmas_gpio_id_irq_handler,
+						   IRQF_TRIGGER_RISING |
+						   IRQF_TRIGGER_FALLING |
+						   IRQF_ONESHOT,
+						   "palmas_usb_id",
+						   palmas_usb);
+		if (status < 0) {
+			dev_err(&pdev->dev,
+				"failed to request handler for id irq\n");
+			return status;
+		}
+	}
+
+	if (palmas_usb->enable_vbus_detection) {
+		palmas_usb->vbus_otg_irq = regmap_irq_get_virq(palmas->irq_data,
+						       PALMAS_VBUS_OTG_IRQ);
+		palmas_usb->vbus_irq = regmap_irq_get_virq(palmas->irq_data,
+							   PALMAS_VBUS_IRQ);
+		status = devm_request_threaded_irq(palmas_usb->dev,
+				palmas_usb->vbus_irq, NULL,
+				palmas_vbus_irq_handler,
+				IRQF_TRIGGER_FALLING | IRQF_TRIGGER_RISING |
+				IRQF_ONESHOT,
+				"palmas_usb_vbus", palmas_usb);
+		if (status < 0) {
+			dev_err(&pdev->dev, "can't get IRQ %d, err %d\n",
+					palmas_usb->vbus_irq, status);
+			return status;
+		}
+	} else if (palmas_usb->enable_gpio_vbus_detection) {
+		/* remux GPIO_1 as VBUSDET */
+		status = palmas_update_bits(palmas,
+			PALMAS_PU_PD_OD_BASE,
+			PALMAS_PRIMARY_SECONDARY_PAD1,
+			PALMAS_PRIMARY_SECONDARY_PAD1_GPIO_1_MASK,
+			(1 << PALMAS_PRIMARY_SECONDARY_PAD1_GPIO_1_SHIFT));
+		if (status < 0) {
+			dev_err(&pdev->dev, "can't remux GPIO1\n");
+			return status;
+		}
+
+		palmas_usb->vbus_otg_irq = regmap_irq_get_virq(palmas->irq_data,
+						       PALMAS_VBUS_OTG_IRQ);
+		palmas_usb->gpio_vbus_irq = gpiod_to_irq(palmas_usb->vbus_gpiod);
+		if (palmas_usb->gpio_vbus_irq < 0) {
+			dev_err(&pdev->dev, "failed to get vbus irq\n");
+			return palmas_usb->gpio_vbus_irq;
+		}
+		status = devm_request_threaded_irq(&pdev->dev,
+						palmas_usb->gpio_vbus_irq,
+						NULL,
+						palmas_vbus_irq_handler,
+						IRQF_TRIGGER_FALLING |
+						IRQF_TRIGGER_RISING |
+						IRQF_ONESHOT,
+						"palmas_usb_vbus",
+						palmas_usb);
+		if (status < 0) {
+			dev_err(&pdev->dev,
+				"failed to request handler for vbus irq\n");
+			return status;
+		}
+	}
+
+	palmas_enable_irq(palmas_usb);
+	/* perform initial detection */
+	if (palmas_usb->enable_gpio_vbus_detection)
+		palmas_vbus_irq_handler(palmas_usb->gpio_vbus_irq, palmas_usb);
+	palmas_gpio_id_detect(&palmas_usb->wq_detectid.work);
+	device_set_wakeup_capable(&pdev->dev, true);
+	return 0;
+}
+
+#ifdef CONFIG_PM_SLEEP
+static int palmas_usb_suspend(struct device *dev)
+{
+	struct palmas_usb *palmas_usb = dev_get_drvdata(dev);
+
+	if (device_may_wakeup(dev)) {
+		if (palmas_usb->enable_vbus_detection)
+			enable_irq_wake(palmas_usb->vbus_irq);
+		if (palmas_usb->enable_gpio_vbus_detection)
+			enable_irq_wake(palmas_usb->gpio_vbus_irq);
+		if (palmas_usb->enable_id_detection)
+			enable_irq_wake(palmas_usb->id_irq);
+		if (palmas_usb->enable_gpio_id_detection)
+			enable_irq_wake(palmas_usb->gpio_id_irq);
+	}
+	return 0;
+}
+
+static int palmas_usb_resume(struct device *dev)
+{
+	struct palmas_usb *palmas_usb = dev_get_drvdata(dev);
+
+	if (device_may_wakeup(dev)) {
+		if (palmas_usb->enable_vbus_detection)
+			disable_irq_wake(palmas_usb->vbus_irq);
+		if (palmas_usb->enable_gpio_vbus_detection)
+			disable_irq_wake(palmas_usb->gpio_vbus_irq);
+		if (palmas_usb->enable_id_detection)
+			disable_irq_wake(palmas_usb->id_irq);
+		if (palmas_usb->enable_gpio_id_detection)
+			disable_irq_wake(palmas_usb->gpio_id_irq);
+	}
+
+	/* check if GPIO states changed while suspend/resume */
+	if (palmas_usb->enable_gpio_vbus_detection)
+		palmas_vbus_irq_handler(palmas_usb->gpio_vbus_irq, palmas_usb);
+	palmas_gpio_id_detect(&palmas_usb->wq_detectid.work);
+
+	return 0;
+};
+#endif
+
+static SIMPLE_DEV_PM_OPS(palmas_pm_ops, palmas_usb_suspend, palmas_usb_resume);
+
+static const struct of_device_id of_palmas_match_tbl[] = {
+	{ .compatible = "ti,palmas-usb", },
+	{ .compatible = "ti,palmas-usb-vid", },
+	{ .compatible = "ti,twl6035-usb", },
+	{ .compatible = "ti,twl6035-usb-vid", },
+	{ /* end */ }
+};
+
+static struct platform_driver palmas_usb_driver = {
+	.probe = palmas_usb_probe,
+	.driver = {
+		.name = "palmas-usb",
+		.of_match_table = of_palmas_match_tbl,
+		.pm = &palmas_pm_ops,
+	},
+};
+
+module_platform_driver(palmas_usb_driver);
+
+MODULE_ALIAS("platform:palmas-usb");
+MODULE_AUTHOR("Graeme Gregory <gg@slimlogic.co.uk>");
+MODULE_DESCRIPTION("Palmas USB transceiver driver");
+MODULE_LICENSE("GPL");
+MODULE_DEVICE_TABLE(of, of_palmas_match_tbl);