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, 250 insertions, 0 deletions

diff --git a/drivers/regulator/mp5416.c b/drivers/regulator/mp5416.c
new file mode 100644
index 000000000..e6794190c
--- /dev/null
+++ b/drivers/regulator/mp5416.c
@@ -0,0 +1,250 @@
+// SPDX-License-Identifier: GPL-2.0+
+//
+// mp5416.c  - regulator driver for mps mp5416
+//
+// Copyright 2020 Monolithic Power Systems, Inc
+//
+// Author: Saravanan Sekar <sravanhome@gmail.com>
+
+#include <linux/err.h>
+#include <linux/i2c.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+#include <linux/regulator/driver.h>
+
+#define MP5416_REG_CTL0			0x00
+#define MP5416_REG_CTL1			0x01
+#define MP5416_REG_CTL2			0x02
+#define MP5416_REG_ILIM			0x03
+#define MP5416_REG_BUCK1		0x04
+#define MP5416_REG_BUCK2		0x05
+#define MP5416_REG_BUCK3		0x06
+#define MP5416_REG_BUCK4		0x07
+#define MP5416_REG_LDO1			0x08
+#define MP5416_REG_LDO2			0x09
+#define MP5416_REG_LDO3			0x0a
+#define MP5416_REG_LDO4			0x0b
+
+#define MP5416_REGULATOR_EN		BIT(7)
+#define MP5416_MASK_VSET		0x7f
+#define MP5416_MASK_BUCK1_ILIM		0xc0
+#define MP5416_MASK_BUCK2_ILIM		0x0c
+#define MP5416_MASK_BUCK3_ILIM		0x30
+#define MP5416_MASK_BUCK4_ILIM		0x03
+#define MP5416_MASK_DVS_SLEWRATE	0xc0
+
+/* values in uV */
+#define MP5416_VOLT1_MIN		600000
+#define MP5416_VOLT1_MAX		2187500
+#define MP5416_VOLT1_STEP		12500
+#define MP5416_VOLT2_MIN		800000
+#define MP5416_VOLT2_MAX		3975000
+#define MP5416_VOLT2_STEP		25000
+
+#define MP5416_VOLT1_RANGE \
+	((MP5416_VOLT1_MAX - MP5416_VOLT1_MIN)/MP5416_VOLT1_STEP + 1)
+#define MP5416_VOLT2_RANGE \
+	((MP5416_VOLT2_MAX - MP5416_VOLT2_MIN)/MP5416_VOLT2_STEP + 1)
+
+#define MP5416BUCK(_name, _id, _ilim, _dreg, _dval, _vsel)		\
+	[MP5416_BUCK ## _id] = {					\
+		.id = MP5416_BUCK ## _id,				\
+		.name = _name,						\
+		.of_match = _name,					\
+		.regulators_node = "regulators",			\
+		.ops = &mp5416_buck_ops,				\
+		.min_uV = MP5416_VOLT ##_vsel## _MIN,			\
+		.uV_step = MP5416_VOLT ##_vsel## _STEP,			\
+		.n_voltages = MP5416_VOLT ##_vsel## _RANGE,		\
+		.curr_table = _ilim,					\
+		.n_current_limits = ARRAY_SIZE(_ilim),			\
+		.csel_reg = MP5416_REG_ILIM,				\
+		.csel_mask = MP5416_MASK_BUCK ## _id ##_ILIM,		\
+		.vsel_reg = MP5416_REG_BUCK ## _id,			\
+		.vsel_mask = MP5416_MASK_VSET,				\
+		.enable_reg = MP5416_REG_BUCK ## _id,			\
+		.enable_mask = MP5416_REGULATOR_EN,			\
+		.ramp_reg = MP5416_REG_CTL2,				\
+		.ramp_mask = MP5416_MASK_DVS_SLEWRATE,			\
+		.ramp_delay_table = mp5416_buck_ramp_table,		\
+		.n_ramp_values = ARRAY_SIZE(mp5416_buck_ramp_table),	\
+		.active_discharge_on	= _dval,			\
+		.active_discharge_reg	= _dreg,			\
+		.active_discharge_mask	= _dval,			\
+		.owner			= THIS_MODULE,			\
+	}
+
+#define MP5416LDO(_name, _id, _dval)					\
+	[MP5416_LDO ## _id] = {						\
+		.id = MP5416_LDO ## _id,				\
+		.name = _name,						\
+		.of_match = _name,					\
+		.regulators_node = "regulators",			\
+		.ops = &mp5416_ldo_ops,					\
+		.min_uV = MP5416_VOLT2_MIN,				\
+		.uV_step = MP5416_VOLT2_STEP,				\
+		.n_voltages = MP5416_VOLT2_RANGE,			\
+		.vsel_reg = MP5416_REG_LDO ##_id,			\
+		.vsel_mask = MP5416_MASK_VSET,				\
+		.enable_reg = MP5416_REG_LDO ##_id,			\
+		.enable_mask = MP5416_REGULATOR_EN,			\
+		.active_discharge_on	= _dval,			\
+		.active_discharge_reg	= MP5416_REG_CTL2,		\
+		.active_discharge_mask	= _dval,			\
+		.owner			= THIS_MODULE,			\
+	}
+
+enum mp5416_regulators {
+	MP5416_BUCK1,
+	MP5416_BUCK2,
+	MP5416_BUCK3,
+	MP5416_BUCK4,
+	MP5416_LDO1,
+	MP5416_LDO2,
+	MP5416_LDO3,
+	MP5416_LDO4,
+	MP5416_MAX_REGULATORS,
+};
+
+static const struct regmap_config mp5416_regmap_config = {
+	.reg_bits = 8,
+	.val_bits = 8,
+	.max_register = 0x0d,
+};
+
+/* Current limits array (in uA)
+ * ILIM1 & ILIM3
+ */
+static const unsigned int mp5416_I_limits1[] = {
+	3800000, 4600000, 5600000, 6800000
+};
+
+/* ILIM2 & ILIM4 */
+static const unsigned int mp5416_I_limits2[] = {
+	2200000, 3200000, 4200000, 5200000
+};
+
+/*
+ * DVS ramp rate BUCK1 to BUCK4
+ * 00: 32mV/us
+ * 01: 16mV/us
+ * 10: 8mV/us
+ * 11: 4mV/us
+ */
+static const unsigned int mp5416_buck_ramp_table[] = {
+	32000, 16000, 8000, 4000
+};
+
+static const struct regulator_ops mp5416_ldo_ops = {
+	.enable			= regulator_enable_regmap,
+	.disable		= regulator_disable_regmap,
+	.is_enabled		= regulator_is_enabled_regmap,
+	.list_voltage		= regulator_list_voltage_linear,
+	.map_voltage		= regulator_map_voltage_linear,
+	.get_voltage_sel	= regulator_get_voltage_sel_regmap,
+	.set_voltage_sel	= regulator_set_voltage_sel_regmap,
+	.set_active_discharge	= regulator_set_active_discharge_regmap,
+};
+
+static const struct regulator_ops mp5416_buck_ops = {
+	.enable			= regulator_enable_regmap,
+	.disable		= regulator_disable_regmap,
+	.is_enabled		= regulator_is_enabled_regmap,
+	.list_voltage		= regulator_list_voltage_linear,
+	.map_voltage		= regulator_map_voltage_linear,
+	.get_voltage_sel	= regulator_get_voltage_sel_regmap,
+	.set_voltage_sel	= regulator_set_voltage_sel_regmap,
+	.set_active_discharge	= regulator_set_active_discharge_regmap,
+	.get_current_limit	= regulator_get_current_limit_regmap,
+	.set_current_limit	= regulator_set_current_limit_regmap,
+	.set_ramp_delay		= regulator_set_ramp_delay_regmap,
+};
+
+static const struct regulator_desc mp5416_regulators_desc[MP5416_MAX_REGULATORS] = {
+	MP5416BUCK("buck1", 1, mp5416_I_limits1, MP5416_REG_CTL1, BIT(0), 1),
+	MP5416BUCK("buck2", 2, mp5416_I_limits2, MP5416_REG_CTL1, BIT(1), 2),
+	MP5416BUCK("buck3", 3, mp5416_I_limits1, MP5416_REG_CTL1, BIT(2), 1),
+	MP5416BUCK("buck4", 4, mp5416_I_limits2, MP5416_REG_CTL2, BIT(5), 2),
+	MP5416LDO("ldo1", 1, BIT(4)),
+	MP5416LDO("ldo2", 2, BIT(3)),
+	MP5416LDO("ldo3", 3, BIT(2)),
+	MP5416LDO("ldo4", 4, BIT(1)),
+};
+
+static const struct regulator_desc mp5496_regulators_desc[MP5416_MAX_REGULATORS] = {
+	MP5416BUCK("buck1", 1, mp5416_I_limits1, MP5416_REG_CTL1, BIT(0), 1),
+	MP5416BUCK("buck2", 2, mp5416_I_limits2, MP5416_REG_CTL1, BIT(1), 1),
+	MP5416BUCK("buck3", 3, mp5416_I_limits1, MP5416_REG_CTL1, BIT(2), 1),
+	MP5416BUCK("buck4", 4, mp5416_I_limits2, MP5416_REG_CTL2, BIT(5), 1),
+	MP5416LDO("ldo1", 1, BIT(4)),
+	MP5416LDO("ldo2", 2, BIT(3)),
+	MP5416LDO("ldo3", 3, BIT(2)),
+	MP5416LDO("ldo4", 4, BIT(1)),
+};
+
+static int mp5416_i2c_probe(struct i2c_client *client)
+{
+	struct device *dev = &client->dev;
+	struct regulator_config config = { NULL, };
+	static const struct regulator_desc *desc;
+	struct regulator_dev *rdev;
+	struct regmap *regmap;
+	int i;
+
+	regmap = devm_regmap_init_i2c(client, &mp5416_regmap_config);
+	if (IS_ERR(regmap)) {
+		dev_err(dev, "Failed to allocate regmap!\n");
+		return PTR_ERR(regmap);
+	}
+
+	desc = i2c_get_match_data(client);
+	if (!desc)
+		return -ENODEV;
+
+	config.dev = dev;
+	config.regmap = regmap;
+
+	for (i = 0; i < MP5416_MAX_REGULATORS; i++) {
+		rdev = devm_regulator_register(dev,
+					       &desc[i],
+					       &config);
+		if (IS_ERR(rdev)) {
+			dev_err(dev, "Failed to register regulator!\n");
+			return PTR_ERR(rdev);
+		}
+	}
+
+	return 0;
+}
+
+static const struct of_device_id mp5416_of_match[] = {
+	{ .compatible = "mps,mp5416", .data = &mp5416_regulators_desc },
+	{ .compatible = "mps,mp5496", .data = &mp5496_regulators_desc },
+	{}
+};
+MODULE_DEVICE_TABLE(of, mp5416_of_match);
+
+static const struct i2c_device_id mp5416_id[] = {
+	{ "mp5416", (kernel_ulong_t)&mp5416_regulators_desc },
+	{ "mp5496", (kernel_ulong_t)&mp5496_regulators_desc },
+	{}
+};
+MODULE_DEVICE_TABLE(i2c, mp5416_id);
+
+static struct i2c_driver mp5416_regulator_driver = {
+	.driver = {
+		.name = "mp5416",
+		.probe_type = PROBE_PREFER_ASYNCHRONOUS,
+		.of_match_table = of_match_ptr(mp5416_of_match),
+	},
+	.probe = mp5416_i2c_probe,
+	.id_table = mp5416_id,
+};
+module_i2c_driver(mp5416_regulator_driver);
+
+MODULE_AUTHOR("Saravanan Sekar <sravanhome@gmail.com>");
+MODULE_DESCRIPTION("MP5416 PMIC regulator driver");
+MODULE_LICENSE("GPL");