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, 370 insertions, 0 deletions

diff --git a/drivers/regulator/mp886x.c b/drivers/regulator/mp886x.c
new file mode 100644
index 000000000..9ad16b04c
--- /dev/null
+++ b/drivers/regulator/mp886x.c
@@ -0,0 +1,370 @@
+// SPDX-License-Identifier: GPL-2.0
+//
+// MP8867/MP8869 regulator driver
+//
+// Copyright (C) 2020 Synaptics Incorporated
+//
+// Author: Jisheng Zhang <jszhang@kernel.org>
+
+#include <linux/gpio/consumer.h>
+#include <linux/i2c.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/regmap.h>
+#include <linux/regulator/driver.h>
+#include <linux/regulator/of_regulator.h>
+
+#define MP886X_VSEL		0x00
+#define  MP886X_V_BOOT		(1 << 7)
+#define MP886X_SYSCNTLREG1	0x01
+#define  MP886X_MODE		(1 << 0)
+#define  MP886X_SLEW_SHIFT	3
+#define  MP886X_SLEW_MASK	(0x7 << MP886X_SLEW_SHIFT)
+#define  MP886X_GO		(1 << 6)
+#define  MP886X_EN		(1 << 7)
+#define MP8869_SYSCNTLREG2	0x02
+
+struct mp886x_cfg_info {
+	const struct regulator_ops *rops;
+	const unsigned int slew_rates[8];
+	const int switch_freq[4];
+	const u8 fs_reg;
+	const u8 fs_shift;
+};
+
+struct mp886x_device_info {
+	struct device *dev;
+	struct regulator_desc desc;
+	struct regulator_init_data *regulator;
+	struct gpio_desc *en_gpio;
+	const struct mp886x_cfg_info *ci;
+	u32 r[2];
+	unsigned int sel;
+};
+
+static void mp886x_set_switch_freq(struct mp886x_device_info *di,
+				   struct regmap *regmap,
+				   u32 freq)
+{
+	const struct mp886x_cfg_info *ci = di->ci;
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(ci->switch_freq); i++) {
+		if (freq == ci->switch_freq[i]) {
+			regmap_update_bits(regmap, ci->fs_reg,
+				  0x3 << ci->fs_shift, i << ci->fs_shift);
+			return;
+		}
+	}
+
+	dev_err(di->dev, "invalid frequency %d\n", freq);
+}
+
+static int mp886x_set_mode(struct regulator_dev *rdev, unsigned int mode)
+{
+	switch (mode) {
+	case REGULATOR_MODE_FAST:
+		regmap_update_bits(rdev->regmap, MP886X_SYSCNTLREG1,
+				   MP886X_MODE, MP886X_MODE);
+		break;
+	case REGULATOR_MODE_NORMAL:
+		regmap_update_bits(rdev->regmap, MP886X_SYSCNTLREG1,
+				   MP886X_MODE, 0);
+		break;
+	default:
+		return -EINVAL;
+	}
+	return 0;
+}
+
+static unsigned int mp886x_get_mode(struct regulator_dev *rdev)
+{
+	u32 val;
+	int ret;
+
+	ret = regmap_read(rdev->regmap, MP886X_SYSCNTLREG1, &val);
+	if (ret < 0)
+		return ret;
+	if (val & MP886X_MODE)
+		return REGULATOR_MODE_FAST;
+	else
+		return REGULATOR_MODE_NORMAL;
+}
+
+static int mp8869_set_voltage_sel(struct regulator_dev *rdev, unsigned int sel)
+{
+	int ret;
+
+	ret = regmap_update_bits(rdev->regmap, MP886X_SYSCNTLREG1,
+				 MP886X_GO, MP886X_GO);
+	if (ret < 0)
+		return ret;
+
+	sel <<= ffs(rdev->desc->vsel_mask) - 1;
+	return regmap_update_bits(rdev->regmap, rdev->desc->vsel_reg,
+				  MP886X_V_BOOT | rdev->desc->vsel_mask, sel);
+}
+
+static inline unsigned int mp8869_scale(unsigned int uv, u32 r1, u32 r2)
+{
+	u32 tmp = uv * r1 / r2;
+
+	return uv + tmp;
+}
+
+static int mp8869_get_voltage_sel(struct regulator_dev *rdev)
+{
+	struct mp886x_device_info *di = rdev_get_drvdata(rdev);
+	int ret, uv;
+	unsigned int val;
+	bool fbloop;
+
+	ret = regmap_read(rdev->regmap, rdev->desc->vsel_reg, &val);
+	if (ret)
+		return ret;
+
+	fbloop = val & MP886X_V_BOOT;
+	if (fbloop) {
+		uv = rdev->desc->min_uV;
+		uv = mp8869_scale(uv, di->r[0], di->r[1]);
+		return regulator_map_voltage_linear(rdev, uv, uv);
+	}
+
+	val &= rdev->desc->vsel_mask;
+	val >>= ffs(rdev->desc->vsel_mask) - 1;
+
+	return val;
+}
+
+static const struct regulator_ops mp8869_regulator_ops = {
+	.set_voltage_sel = mp8869_set_voltage_sel,
+	.get_voltage_sel = mp8869_get_voltage_sel,
+	.set_voltage_time_sel = regulator_set_voltage_time_sel,
+	.map_voltage = regulator_map_voltage_linear,
+	.list_voltage = regulator_list_voltage_linear,
+	.enable = regulator_enable_regmap,
+	.disable = regulator_disable_regmap,
+	.is_enabled = regulator_is_enabled_regmap,
+	.set_mode = mp886x_set_mode,
+	.get_mode = mp886x_get_mode,
+	.set_ramp_delay = regulator_set_ramp_delay_regmap,
+};
+
+static const struct mp886x_cfg_info mp8869_ci = {
+	.rops = &mp8869_regulator_ops,
+	.slew_rates = {
+		40000,
+		30000,
+		20000,
+		10000,
+		5000,
+		2500,
+		1250,
+		625,
+	},
+	.switch_freq = {
+		500000,
+		750000,
+		1000000,
+		1250000,
+	},
+	.fs_reg = MP8869_SYSCNTLREG2,
+	.fs_shift = 4,
+};
+
+static int mp8867_set_voltage_sel(struct regulator_dev *rdev, unsigned int sel)
+{
+	struct mp886x_device_info *di = rdev_get_drvdata(rdev);
+	int ret, delta;
+
+	ret = mp8869_set_voltage_sel(rdev, sel);
+	if (ret < 0)
+		return ret;
+
+	delta = di->sel - sel;
+	if (abs(delta) <= 5)
+		ret = regmap_update_bits(rdev->regmap, MP886X_SYSCNTLREG1,
+					 MP886X_GO, 0);
+	di->sel = sel;
+
+	return ret;
+}
+
+static int mp8867_get_voltage_sel(struct regulator_dev *rdev)
+{
+	struct mp886x_device_info *di = rdev_get_drvdata(rdev);
+	int ret, uv;
+	unsigned int val;
+	bool fbloop;
+
+	ret = regmap_read(rdev->regmap, rdev->desc->vsel_reg, &val);
+	if (ret)
+		return ret;
+
+	fbloop = val & MP886X_V_BOOT;
+
+	val &= rdev->desc->vsel_mask;
+	val >>= ffs(rdev->desc->vsel_mask) - 1;
+
+	if (fbloop) {
+		uv = regulator_list_voltage_linear(rdev, val);
+		uv = mp8869_scale(uv, di->r[0], di->r[1]);
+		return regulator_map_voltage_linear(rdev, uv, uv);
+	}
+
+	return val;
+}
+
+static const struct regulator_ops mp8867_regulator_ops = {
+	.set_voltage_sel = mp8867_set_voltage_sel,
+	.get_voltage_sel = mp8867_get_voltage_sel,
+	.set_voltage_time_sel = regulator_set_voltage_time_sel,
+	.map_voltage = regulator_map_voltage_linear,
+	.list_voltage = regulator_list_voltage_linear,
+	.enable = regulator_enable_regmap,
+	.disable = regulator_disable_regmap,
+	.is_enabled = regulator_is_enabled_regmap,
+	.set_mode = mp886x_set_mode,
+	.get_mode = mp886x_get_mode,
+	.set_ramp_delay = regulator_set_ramp_delay_regmap,
+};
+
+static const struct mp886x_cfg_info mp8867_ci = {
+	.rops = &mp8867_regulator_ops,
+	.slew_rates = {
+		64000,
+		32000,
+		16000,
+		8000,
+		4000,
+		2000,
+		1000,
+		500,
+	},
+	.switch_freq = {
+		500000,
+		750000,
+		1000000,
+		1500000,
+	},
+	.fs_reg = MP886X_SYSCNTLREG1,
+	.fs_shift = 1,
+};
+
+static int mp886x_regulator_register(struct mp886x_device_info *di,
+				     struct regulator_config *config)
+{
+	struct regulator_desc *rdesc = &di->desc;
+	struct regulator_dev *rdev;
+
+	rdesc->name = "mp886x-reg";
+	rdesc->supply_name = "vin";
+	rdesc->ops = di->ci->rops;
+	rdesc->type = REGULATOR_VOLTAGE;
+	rdesc->n_voltages = 128;
+	rdesc->enable_reg = MP886X_SYSCNTLREG1;
+	rdesc->enable_mask = MP886X_EN;
+	rdesc->min_uV = 600000;
+	rdesc->uV_step = 10000;
+	rdesc->vsel_reg = MP886X_VSEL;
+	rdesc->vsel_mask = 0x3f;
+	rdesc->ramp_reg = MP886X_SYSCNTLREG1;
+	rdesc->ramp_mask = MP886X_SLEW_MASK;
+	rdesc->ramp_delay_table = di->ci->slew_rates;
+	rdesc->n_ramp_values = ARRAY_SIZE(di->ci->slew_rates);
+	rdesc->owner = THIS_MODULE;
+
+	rdev = devm_regulator_register(di->dev, &di->desc, config);
+	if (IS_ERR(rdev))
+		return PTR_ERR(rdev);
+	di->sel = rdesc->ops->get_voltage_sel(rdev);
+	return 0;
+}
+
+static const struct regmap_config mp886x_regmap_config = {
+	.reg_bits = 8,
+	.val_bits = 8,
+};
+
+static int mp886x_i2c_probe(struct i2c_client *client)
+{
+	struct device *dev = &client->dev;
+	struct device_node *np = dev->of_node;
+	struct mp886x_device_info *di;
+	struct regulator_config config = { };
+	struct regmap *regmap;
+	u32 freq;
+	int ret;
+
+	di = devm_kzalloc(dev, sizeof(struct mp886x_device_info), GFP_KERNEL);
+	if (!di)
+		return -ENOMEM;
+
+	di->regulator = of_get_regulator_init_data(dev, np, &di->desc);
+	if (!di->regulator) {
+		dev_err(dev, "Platform data not found!\n");
+		return -EINVAL;
+	}
+
+	ret = of_property_read_u32_array(np, "mps,fb-voltage-divider",
+					 di->r, 2);
+	if (ret)
+		return ret;
+
+	di->en_gpio = devm_gpiod_get(dev, "enable", GPIOD_OUT_HIGH);
+	if (IS_ERR(di->en_gpio))
+		return PTR_ERR(di->en_gpio);
+
+	di->ci = i2c_get_match_data(client);
+	di->dev = dev;
+
+	regmap = devm_regmap_init_i2c(client, &mp886x_regmap_config);
+	if (IS_ERR(regmap)) {
+		dev_err(dev, "Failed to allocate regmap!\n");
+		return PTR_ERR(regmap);
+	}
+	i2c_set_clientdata(client, di);
+
+	config.dev = di->dev;
+	config.init_data = di->regulator;
+	config.regmap = regmap;
+	config.driver_data = di;
+	config.of_node = np;
+
+	if (!of_property_read_u32(np, "mps,switch-frequency-hz", &freq))
+		mp886x_set_switch_freq(di, regmap, freq);
+
+	ret = mp886x_regulator_register(di, &config);
+	if (ret < 0)
+		dev_err(dev, "Failed to register regulator!\n");
+	return ret;
+}
+
+static const struct of_device_id mp886x_dt_ids[] = {
+	{ .compatible = "mps,mp8867", .data = &mp8867_ci },
+	{ .compatible = "mps,mp8869", .data = &mp8869_ci },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, mp886x_dt_ids);
+
+static const struct i2c_device_id mp886x_id[] = {
+	{ "mp8867", (kernel_ulong_t)&mp8867_ci },
+	{ "mp8869", (kernel_ulong_t)&mp8869_ci },
+	{ },
+};
+MODULE_DEVICE_TABLE(i2c, mp886x_id);
+
+static struct i2c_driver mp886x_regulator_driver = {
+	.driver = {
+		.name = "mp886x-regulator",
+		.probe_type = PROBE_PREFER_ASYNCHRONOUS,
+		.of_match_table = mp886x_dt_ids,
+	},
+	.probe = mp886x_i2c_probe,
+	.id_table = mp886x_id,
+};
+module_i2c_driver(mp886x_regulator_driver);
+
+MODULE_AUTHOR("Jisheng Zhang <jszhang@kernel.org>");
+MODULE_DESCRIPTION("MP886x regulator driver");
+MODULE_LICENSE("GPL v2");