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, 330 insertions, 0 deletions

diff --git a/drivers/regulator/mpq7920.c b/drivers/regulator/mpq7920.c
new file mode 100644
index 000000000..a670e0989
--- /dev/null
+++ b/drivers/regulator/mpq7920.c
@@ -0,0 +1,330 @@
+// SPDX-License-Identifier: GPL-2.0+
+//
+// mpq7920.c  - regulator driver for mps mpq7920
+//
+// Copyright 2019 Monolithic Power Systems, Inc
+//
+// Author: Saravanan Sekar <sravanhome@gmail.com>
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/err.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/regulator/driver.h>
+#include <linux/regulator/of_regulator.h>
+#include <linux/i2c.h>
+#include <linux/regmap.h>
+#include "mpq7920.h"
+
+#define MPQ7920_BUCK_VOLT_RANGE \
+	((MPQ7920_VOLT_MAX - MPQ7920_BUCK_VOLT_MIN)/MPQ7920_VOLT_STEP + 1)
+#define MPQ7920_LDO_VOLT_RANGE \
+	((MPQ7920_VOLT_MAX - MPQ7920_LDO_VOLT_MIN)/MPQ7920_VOLT_STEP + 1)
+
+#define MPQ7920BUCK(_name, _id, _ilim)					\
+	[MPQ7920_BUCK ## _id] = {					\
+		.id = MPQ7920_BUCK ## _id,				\
+		.name = _name,						\
+		.of_match = _name,					\
+		.regulators_node = "regulators",			\
+		.of_parse_cb = mpq7920_parse_cb,			\
+		.ops = &mpq7920_buck_ops,				\
+		.min_uV = MPQ7920_BUCK_VOLT_MIN,			\
+		.uV_step = MPQ7920_VOLT_STEP,				\
+		.n_voltages = MPQ7920_BUCK_VOLT_RANGE,			\
+		.curr_table = _ilim,					\
+		.n_current_limits = ARRAY_SIZE(_ilim),			\
+		.csel_reg = MPQ7920_BUCK ##_id## _REG_C,		\
+		.csel_mask = MPQ7920_MASK_BUCK_ILIM,			\
+		.enable_reg = MPQ7920_REG_REGULATOR_EN,			\
+		.enable_mask = BIT(MPQ7920_REGULATOR_EN_OFFSET -	\
+					 MPQ7920_BUCK ## _id),		\
+		.vsel_reg = MPQ7920_BUCK ##_id## _REG_A,		\
+		.vsel_mask = MPQ7920_MASK_VREF,				\
+		.active_discharge_on	= MPQ7920_DISCHARGE_ON,		\
+		.active_discharge_reg	= MPQ7920_BUCK ##_id## _REG_B,	\
+		.active_discharge_mask	= MPQ7920_MASK_DISCHARGE,	\
+		.soft_start_reg		= MPQ7920_BUCK ##_id## _REG_C,	\
+		.soft_start_mask	= MPQ7920_MASK_SOFTSTART,	\
+		.owner			= THIS_MODULE,			\
+	}
+
+#define MPQ7920LDO(_name, _id, _ops, _ilim, _ilim_sz, _creg, _cmask)	\
+	[MPQ7920_LDO ## _id] = {					\
+		.id = MPQ7920_LDO ## _id,				\
+		.name = _name,						\
+		.of_match = _name,					\
+		.regulators_node = "regulators",			\
+		.ops = _ops,						\
+		.min_uV = MPQ7920_LDO_VOLT_MIN,				\
+		.uV_step = MPQ7920_VOLT_STEP,				\
+		.n_voltages = MPQ7920_LDO_VOLT_RANGE,			\
+		.vsel_reg = MPQ7920_LDO ##_id## _REG_A,			\
+		.vsel_mask = MPQ7920_MASK_VREF,				\
+		.curr_table = _ilim,					\
+		.n_current_limits = _ilim_sz,				\
+		.csel_reg = _creg,					\
+		.csel_mask = _cmask,					\
+		.enable_reg = (_id == 1) ? 0 : MPQ7920_REG_REGULATOR_EN,\
+		.enable_mask = BIT(MPQ7920_REGULATOR_EN_OFFSET -	\
+					MPQ7920_LDO ##_id + 1),		\
+		.active_discharge_on	= MPQ7920_DISCHARGE_ON,		\
+		.active_discharge_mask	= MPQ7920_MASK_DISCHARGE,	\
+		.active_discharge_reg	= MPQ7920_LDO ##_id## _REG_B,	\
+		.type			= REGULATOR_VOLTAGE,		\
+		.owner			= THIS_MODULE,			\
+	}
+
+enum mpq7920_regulators {
+	MPQ7920_BUCK1,
+	MPQ7920_BUCK2,
+	MPQ7920_BUCK3,
+	MPQ7920_BUCK4,
+	MPQ7920_LDO1, /* LDORTC */
+	MPQ7920_LDO2,
+	MPQ7920_LDO3,
+	MPQ7920_LDO4,
+	MPQ7920_LDO5,
+	MPQ7920_MAX_REGULATORS,
+};
+
+struct mpq7920_regulator_info {
+	struct regmap *regmap;
+	struct regulator_desc *rdesc;
+};
+
+static const struct regmap_config mpq7920_regmap_config = {
+	.reg_bits = 8,
+	.val_bits = 8,
+	.max_register = 0x25,
+};
+
+/* Current limits array (in uA)
+ * ILIM1 & ILIM3
+ */
+static const unsigned int mpq7920_I_limits1[] = {
+	4600000, 6600000, 7600000, 9300000
+};
+
+/* ILIM2 & ILIM4 */
+static const unsigned int mpq7920_I_limits2[] = {
+	2700000, 3900000, 5100000, 6100000
+};
+
+/* LDO4 & LDO5 */
+static const unsigned int mpq7920_I_limits3[] = {
+	300000, 700000
+};
+
+static int mpq7920_set_ramp_delay(struct regulator_dev *rdev, int ramp_delay);
+static int mpq7920_parse_cb(struct device_node *np,
+				const struct regulator_desc *rdesc,
+				struct regulator_config *config);
+
+/* RTCLDO not controllable, always ON */
+static const struct regulator_ops mpq7920_ldortc_ops = {
+	.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,
+};
+
+static const struct regulator_ops mpq7920_ldo_wo_current_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 mpq7920_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,
+	.get_current_limit	= regulator_get_current_limit_regmap,
+	.set_current_limit	= regulator_set_current_limit_regmap,
+};
+
+static const struct regulator_ops mpq7920_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,
+	.set_soft_start		= regulator_set_soft_start_regmap,
+	.set_ramp_delay		= mpq7920_set_ramp_delay,
+};
+
+static struct regulator_desc mpq7920_regulators_desc[MPQ7920_MAX_REGULATORS] = {
+	MPQ7920BUCK("buck1", 1, mpq7920_I_limits1),
+	MPQ7920BUCK("buck2", 2, mpq7920_I_limits2),
+	MPQ7920BUCK("buck3", 3, mpq7920_I_limits1),
+	MPQ7920BUCK("buck4", 4, mpq7920_I_limits2),
+	MPQ7920LDO("ldortc", 1, &mpq7920_ldortc_ops, NULL, 0, 0, 0),
+	MPQ7920LDO("ldo2", 2, &mpq7920_ldo_wo_current_ops, NULL, 0, 0, 0),
+	MPQ7920LDO("ldo3", 3, &mpq7920_ldo_wo_current_ops, NULL, 0, 0, 0),
+	MPQ7920LDO("ldo4", 4, &mpq7920_ldo_ops, mpq7920_I_limits3,
+			ARRAY_SIZE(mpq7920_I_limits3), MPQ7920_LDO4_REG_B,
+			MPQ7920_MASK_LDO_ILIM),
+	MPQ7920LDO("ldo5", 5, &mpq7920_ldo_ops, mpq7920_I_limits3,
+			ARRAY_SIZE(mpq7920_I_limits3), MPQ7920_LDO5_REG_B,
+			MPQ7920_MASK_LDO_ILIM),
+};
+
+/*
+ * DVS ramp rate BUCK1 to BUCK4
+ * 00-01: Reserved
+ * 10: 8mV/us
+ * 11: 4mV/us
+ */
+static int mpq7920_set_ramp_delay(struct regulator_dev *rdev, int ramp_delay)
+{
+	unsigned int ramp_val;
+
+	if (ramp_delay > 8000 || ramp_delay < 0)
+		return -EINVAL;
+
+	if (ramp_delay <= 4000)
+		ramp_val = 3;
+	else
+		ramp_val = 2;
+
+	return regmap_update_bits(rdev->regmap, MPQ7920_REG_CTL0,
+				  MPQ7920_MASK_DVS_SLEWRATE, ramp_val << 6);
+}
+
+static int mpq7920_parse_cb(struct device_node *np,
+				const struct regulator_desc *desc,
+				struct regulator_config *config)
+{
+	uint8_t val;
+	int ret;
+	struct mpq7920_regulator_info *info = config->driver_data;
+	struct regulator_desc *rdesc = &info->rdesc[desc->id];
+
+	if (of_property_read_bool(np, "mps,buck-ovp-disable")) {
+		regmap_update_bits(config->regmap,
+				MPQ7920_BUCK1_REG_B + (rdesc->id * 4),
+				MPQ7920_MASK_OVP, MPQ7920_OVP_DISABLE);
+	}
+
+	ret = of_property_read_u8(np, "mps,buck-phase-delay", &val);
+	if (!ret) {
+		regmap_update_bits(config->regmap,
+				MPQ7920_BUCK1_REG_C + (rdesc->id * 4),
+				MPQ7920_MASK_BUCK_PHASE_DEALY,
+				(val & 3) << 4);
+	}
+
+	ret = of_property_read_u8(np, "mps,buck-softstart", &val);
+	if (!ret)
+		rdesc->soft_start_val_on = (val & 3) << 2;
+
+	return 0;
+}
+
+static void mpq7920_parse_dt(struct device *dev,
+		 struct mpq7920_regulator_info *info)
+{
+	int ret;
+	struct device_node *np = dev->of_node;
+	uint8_t freq;
+
+	np = of_get_child_by_name(np, "regulators");
+	if (!np) {
+		dev_err(dev, "missing 'regulators' subnode in DT\n");
+		return;
+	}
+
+	ret = of_property_read_u8(np, "mps,switch-freq", &freq);
+	if (!ret) {
+		regmap_update_bits(info->regmap, MPQ7920_REG_CTL0,
+					MPQ7920_MASK_SWITCH_FREQ,
+					(freq & 3) << 4);
+	}
+
+	of_node_put(np);
+}
+
+static int mpq7920_i2c_probe(struct i2c_client *client)
+{
+	struct device *dev = &client->dev;
+	struct mpq7920_regulator_info *info;
+	struct regulator_config config = { NULL, };
+	struct regulator_dev *rdev;
+	struct regmap *regmap;
+	int i;
+
+	info = devm_kzalloc(dev, sizeof(struct mpq7920_regulator_info),
+				GFP_KERNEL);
+	if (!info)
+		return -ENOMEM;
+
+	info->rdesc = mpq7920_regulators_desc;
+	regmap = devm_regmap_init_i2c(client, &mpq7920_regmap_config);
+	if (IS_ERR(regmap)) {
+		dev_err(dev, "Failed to allocate regmap!\n");
+		return PTR_ERR(regmap);
+	}
+
+	i2c_set_clientdata(client, info);
+	info->regmap = regmap;
+	if (client->dev.of_node)
+		mpq7920_parse_dt(&client->dev, info);
+
+	config.dev = dev;
+	config.regmap = regmap;
+	config.driver_data = info;
+
+	for (i = 0; i < MPQ7920_MAX_REGULATORS; i++) {
+		rdev = devm_regulator_register(dev,
+					       &mpq7920_regulators_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 mpq7920_of_match[] = {
+	{ .compatible = "mps,mpq7920"},
+	{},
+};
+MODULE_DEVICE_TABLE(of, mpq7920_of_match);
+
+static const struct i2c_device_id mpq7920_id[] = {
+	{ "mpq7920", },
+	{ },
+};
+MODULE_DEVICE_TABLE(i2c, mpq7920_id);
+
+static struct i2c_driver mpq7920_regulator_driver = {
+	.driver = {
+		.name = "mpq7920",
+		.probe_type = PROBE_PREFER_ASYNCHRONOUS,
+		.of_match_table = mpq7920_of_match,
+	},
+	.probe = mpq7920_i2c_probe,
+	.id_table = mpq7920_id,
+};
+module_i2c_driver(mpq7920_regulator_driver);
+
+MODULE_AUTHOR("Saravanan Sekar <sravanhome@gmail.com>");
+MODULE_DESCRIPTION("MPQ7920 PMIC regulator driver");
+MODULE_LICENSE("GPL");