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, 321 insertions, 0 deletions

diff --git a/drivers/regulator/rt5739.c b/drivers/regulator/rt5739.c
new file mode 100644
index 000000000..00706cba9
--- /dev/null
+++ b/drivers/regulator/rt5739.c
@@ -0,0 +1,321 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Device driver for RT5739 regulator
+ *
+ * Copyright (C) 2023 Richtek Technology Corp.
+ *
+ * Author: ChiYuan Huang <cy_huang@richtek.com>
+ */
+
+#include <linux/bits.h>
+#include <linux/gpio/consumer.h>
+#include <linux/i2c.h>
+#include <linux/kernel.h>
+#include <linux/property.h>
+#include <linux/regmap.h>
+#include <linux/regulator/driver.h>
+#include <linux/regulator/of_regulator.h>
+
+#define RT5739_AUTO_MODE	0
+#define RT5739_FPWM_MODE	1
+
+#define RT5739_REG_NSEL0	0x00
+#define RT5739_REG_NSEL1	0x01
+#define RT5739_REG_CNTL1	0x02
+#define RT5739_REG_ID1		0x03
+#define RT5739_REG_ID2		0x04
+#define RT5739_REG_MON		0x05
+#define RT5739_REG_CNTL2	0x06
+#define RT5739_REG_CNTL4	0x08
+
+#define RT5739_VSEL_MASK	GENMASK(7, 0)
+#define RT5739_MODEVSEL1_MASK	BIT(1)
+#define RT5739_MODEVSEL0_MASK	BIT(0)
+#define RT5739_VID_MASK		GENMASK(7, 5)
+#define RT5739_DID_MASK		GENMASK(3, 0)
+#define RT5739_ACTD_MASK	BIT(7)
+#define RT5739_ENVSEL1_MASK	BIT(1)
+#define RT5739_ENVSEL0_MASK	BIT(0)
+
+#define RT5733_CHIPDIE_ID	0x1
+#define RT5733_VOLT_MINUV	270000
+#define RT5733_VOLT_MAXUV	1401250
+#define RT5733_VOLT_STPUV	6250
+#define RT5733_N_VOLTS		182
+
+#define RT5739_VOLT_MINUV	300000
+#define RT5739_VOLT_MAXUV	1300000
+#define RT5739_VOLT_STPUV	5000
+#define RT5739_N_VOLTS		201
+#define RT5739_I2CRDY_TIMEUS	1000
+
+static int rt5739_set_mode(struct regulator_dev *rdev, unsigned int mode)
+{
+	const struct regulator_desc *desc = rdev->desc;
+	struct regmap *regmap = rdev_get_regmap(rdev);
+	unsigned int mask, val;
+
+	if (desc->vsel_reg == RT5739_REG_NSEL0)
+		mask = RT5739_MODEVSEL0_MASK;
+	else
+		mask = RT5739_MODEVSEL1_MASK;
+
+	switch (mode) {
+	case REGULATOR_MODE_FAST:
+		val = mask;
+		break;
+	case REGULATOR_MODE_NORMAL:
+		val = 0;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	return regmap_update_bits(regmap, RT5739_REG_CNTL1, mask, val);
+}
+
+static unsigned int rt5739_get_mode(struct regulator_dev *rdev)
+{
+	const struct regulator_desc *desc = rdev->desc;
+	struct regmap *regmap = rdev_get_regmap(rdev);
+	unsigned int mask, val;
+	int ret;
+
+	if (desc->vsel_reg == RT5739_REG_NSEL0)
+		mask = RT5739_MODEVSEL0_MASK;
+	else
+		mask = RT5739_MODEVSEL1_MASK;
+
+	ret = regmap_read(regmap, RT5739_REG_CNTL1, &val);
+	if (ret)
+		return REGULATOR_MODE_INVALID;
+
+	if (val & mask)
+		return REGULATOR_MODE_FAST;
+
+	return REGULATOR_MODE_NORMAL;
+}
+
+static int rt5739_set_suspend_voltage(struct regulator_dev *rdev, int uV)
+{
+	const struct regulator_desc *desc = rdev->desc;
+	struct regmap *regmap = rdev_get_regmap(rdev);
+	unsigned int reg, vsel;
+	int max_uV;
+
+	max_uV = desc->min_uV + desc->uV_step * (desc->n_voltages - 1);
+
+	if (uV < desc->min_uV || uV > max_uV)
+		return -EINVAL;
+
+	if (desc->vsel_reg == RT5739_REG_NSEL0)
+		reg = RT5739_REG_NSEL1;
+	else
+		reg = RT5739_REG_NSEL0;
+
+	vsel = (uV - desc->min_uV) / desc->uV_step;
+	return regmap_write(regmap, reg, vsel);
+}
+
+static int rt5739_set_suspend_enable(struct regulator_dev *rdev)
+{
+	const struct regulator_desc *desc = rdev->desc;
+	struct regmap *regmap = rdev_get_regmap(rdev);
+	unsigned int mask;
+
+	if (desc->vsel_reg == RT5739_REG_NSEL0)
+		mask = RT5739_ENVSEL1_MASK;
+	else
+		mask = RT5739_ENVSEL0_MASK;
+
+	return regmap_update_bits(regmap, desc->enable_reg, mask, mask);
+}
+
+static int rt5739_set_suspend_disable(struct regulator_dev *rdev)
+{
+	const struct regulator_desc *desc = rdev->desc;
+	struct regmap *regmap = rdev_get_regmap(rdev);
+	unsigned int mask;
+
+	if (desc->vsel_reg == RT5739_REG_NSEL0)
+		mask = RT5739_ENVSEL1_MASK;
+	else
+		mask = RT5739_ENVSEL0_MASK;
+
+	return regmap_update_bits(regmap, desc->enable_reg, mask, 0);
+}
+
+static int rt5739_set_suspend_mode(struct regulator_dev *rdev,
+				   unsigned int mode)
+{
+	const struct regulator_desc *desc = rdev->desc;
+	struct regmap *regmap = rdev_get_regmap(rdev);
+	unsigned int mask, val;
+
+	if (desc->vsel_reg == RT5739_REG_NSEL0)
+		mask = RT5739_MODEVSEL1_MASK;
+	else
+		mask = RT5739_MODEVSEL0_MASK;
+
+	switch (mode) {
+	case REGULATOR_MODE_FAST:
+		val = mask;
+		break;
+	case REGULATOR_MODE_NORMAL:
+		val = 0;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	return regmap_update_bits(regmap, RT5739_REG_CNTL1, mask, val);
+}
+
+static const struct regulator_ops rt5739_regulator_ops = {
+	.list_voltage = regulator_list_voltage_linear,
+	.get_voltage_sel = regulator_get_voltage_sel_regmap,
+	.set_voltage_sel = regulator_set_voltage_sel_regmap,
+	.enable	= regulator_enable_regmap,
+	.disable = regulator_disable_regmap,
+	.is_enabled = regulator_is_enabled_regmap,
+	.set_active_discharge = regulator_set_active_discharge_regmap,
+	.set_mode = rt5739_set_mode,
+	.get_mode = rt5739_get_mode,
+	.set_suspend_voltage = rt5739_set_suspend_voltage,
+	.set_suspend_enable = rt5739_set_suspend_enable,
+	.set_suspend_disable = rt5739_set_suspend_disable,
+	.set_suspend_mode = rt5739_set_suspend_mode,
+};
+
+static unsigned int rt5739_of_map_mode(unsigned int mode)
+{
+	switch (mode) {
+	case RT5739_AUTO_MODE:
+		return REGULATOR_MODE_NORMAL;
+	case RT5739_FPWM_MODE:
+		return REGULATOR_MODE_FAST;
+	default:
+		return REGULATOR_MODE_INVALID;
+	}
+}
+
+static void rt5739_init_regulator_desc(struct regulator_desc *desc,
+				       bool vsel_active_high, u8 did)
+{
+	/* Fixed */
+	desc->name = "rt5739-regulator";
+	desc->owner = THIS_MODULE;
+	desc->ops = &rt5739_regulator_ops;
+	desc->vsel_mask = RT5739_VSEL_MASK;
+	desc->enable_reg = RT5739_REG_CNTL2;
+	desc->active_discharge_reg = RT5739_REG_CNTL1;
+	desc->active_discharge_mask = RT5739_ACTD_MASK;
+	desc->active_discharge_on = RT5739_ACTD_MASK;
+	desc->of_map_mode = rt5739_of_map_mode;
+
+	/* Assigned by vsel level */
+	if (vsel_active_high) {
+		desc->vsel_reg = RT5739_REG_NSEL1;
+		desc->enable_mask = RT5739_ENVSEL1_MASK;
+	} else {
+		desc->vsel_reg = RT5739_REG_NSEL0;
+		desc->enable_mask = RT5739_ENVSEL0_MASK;
+	}
+
+	/* Assigned by CHIPDIE ID */
+	switch (did) {
+	case RT5733_CHIPDIE_ID:
+		desc->n_voltages = RT5733_N_VOLTS;
+		desc->min_uV = RT5733_VOLT_MINUV;
+		desc->uV_step = RT5733_VOLT_STPUV;
+		break;
+	default:
+		desc->n_voltages = RT5739_N_VOLTS;
+		desc->min_uV = RT5739_VOLT_MINUV;
+		desc->uV_step = RT5739_VOLT_STPUV;
+		break;
+	}
+}
+
+static bool rt5739_volatile_reg(struct device *dev, unsigned int reg)
+{
+	return reg == RT5739_REG_MON;
+}
+
+static const struct regmap_config rt5739_regmap_config = {
+	.name = "rt5739",
+	.reg_bits = 8,
+	.val_bits = 8,
+	.max_register = RT5739_REG_CNTL4,
+	.cache_type = REGCACHE_MAPLE,
+	.volatile_reg = rt5739_volatile_reg,
+};
+
+static int rt5739_probe(struct i2c_client *i2c)
+{
+	struct device *dev = &i2c->dev;
+	struct regulator_desc *desc;
+	struct regmap *regmap;
+	struct gpio_desc *enable_gpio;
+	struct regulator_config cfg = {};
+	struct regulator_dev *rdev;
+	bool vsel_acth;
+	unsigned int vid;
+	int ret;
+
+	desc = devm_kzalloc(dev, sizeof(*desc), GFP_KERNEL);
+	if (!desc)
+		return -ENOMEM;
+
+	enable_gpio = devm_gpiod_get_optional(dev, "enable", GPIOD_OUT_HIGH);
+	if (IS_ERR(enable_gpio))
+		return dev_err_probe(dev, PTR_ERR(enable_gpio), "Failed to get 'enable' gpio\n");
+	else if (enable_gpio)
+		usleep_range(RT5739_I2CRDY_TIMEUS, RT5739_I2CRDY_TIMEUS + 1000);
+
+	regmap = devm_regmap_init_i2c(i2c, &rt5739_regmap_config);
+	if (IS_ERR(regmap))
+		return dev_err_probe(dev, PTR_ERR(regmap), "Failed to init regmap\n");
+
+	ret = regmap_read(regmap, RT5739_REG_ID1, &vid);
+	if (ret)
+		return dev_err_probe(dev, ret, "Failed to read VID\n");
+
+	/* RT5739: (VID & MASK) must be 0 */
+	if (vid & RT5739_VID_MASK)
+		return dev_err_probe(dev, -ENODEV, "Incorrect VID (0x%02x)\n", vid);
+
+	vsel_acth = device_property_read_bool(dev, "richtek,vsel-active-high");
+
+	rt5739_init_regulator_desc(desc, vsel_acth, vid & RT5739_DID_MASK);
+
+	cfg.dev = dev;
+	cfg.of_node = dev_of_node(dev);
+	cfg.init_data = of_get_regulator_init_data(dev, dev_of_node(dev), desc);
+	rdev = devm_regulator_register(dev, desc, &cfg);
+	if (IS_ERR(rdev))
+		return dev_err_probe(dev, PTR_ERR(rdev), "Failed to register regulator\n");
+
+	return 0;
+}
+
+static const struct of_device_id rt5739_device_table[] = {
+	{ .compatible = "richtek,rt5733" },
+	{ .compatible = "richtek,rt5739" },
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, rt5739_device_table);
+
+static struct i2c_driver rt5739_driver = {
+	.driver = {
+		.name = "rt5739",
+		.probe_type = PROBE_PREFER_ASYNCHRONOUS,
+		.of_match_table = rt5739_device_table,
+	},
+	.probe = rt5739_probe,
+};
+module_i2c_driver(rt5739_driver);
+
+MODULE_AUTHOR("ChiYuan Huang <cy_huang@richtek.com>");
+MODULE_DESCRIPTION("Richtek RT5739 regulator driver");
+MODULE_LICENSE("GPL");