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, 367 insertions, 0 deletions

diff --git a/drivers/mfd/pf1550.c b/drivers/mfd/pf1550.c
new file mode 100644
index 000000000..c4f567c05
--- /dev/null
+++ b/drivers/mfd/pf1550.c
@@ -0,0 +1,367 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Core driver for the PF1550
+ *
+ * Copyright (C) 2016 Freescale Semiconductor, Inc.
+ * Robin Gong <yibin.gong@freescale.com>
+ *
+ * Portions Copyright (c) 2025 Savoir-faire Linux Inc.
+ * Samuel Kayode <samuel.kayode@savoirfairelinux.com>
+ */
+
+#include <linux/err.h>
+#include <linux/i2c.h>
+#include <linux/interrupt.h>
+#include <linux/mfd/core.h>
+#include <linux/mfd/pf1550.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/regmap.h>
+
+static const struct regmap_config pf1550_regmap_config = {
+	.reg_bits = 8,
+	.val_bits = 8,
+	.max_register = PF1550_PMIC_REG_END,
+};
+
+static const struct regmap_irq pf1550_irqs[] = {
+	REGMAP_IRQ_REG(PF1550_IRQ_CHG, 0, IRQ_CHG),
+	REGMAP_IRQ_REG(PF1550_IRQ_REGULATOR, 0, IRQ_REGULATOR),
+	REGMAP_IRQ_REG(PF1550_IRQ_ONKEY, 0, IRQ_ONKEY),
+};
+
+static const struct regmap_irq_chip pf1550_irq_chip = {
+	.name = "pf1550",
+	.status_base = PF1550_PMIC_REG_INT_CATEGORY,
+	.init_ack_masked = 1,
+	.num_regs = 1,
+	.irqs = pf1550_irqs,
+	.num_irqs = ARRAY_SIZE(pf1550_irqs),
+};
+
+static const struct regmap_irq pf1550_regulator_irqs[] = {
+	REGMAP_IRQ_REG(PF1550_PMIC_IRQ_SW1_LS, 0, PMIC_IRQ_SW1_LS),
+	REGMAP_IRQ_REG(PF1550_PMIC_IRQ_SW2_LS, 0, PMIC_IRQ_SW2_LS),
+	REGMAP_IRQ_REG(PF1550_PMIC_IRQ_SW3_LS, 0, PMIC_IRQ_SW3_LS),
+	REGMAP_IRQ_REG(PF1550_PMIC_IRQ_SW1_HS, 3, PMIC_IRQ_SW1_HS),
+	REGMAP_IRQ_REG(PF1550_PMIC_IRQ_SW2_HS, 3, PMIC_IRQ_SW2_HS),
+	REGMAP_IRQ_REG(PF1550_PMIC_IRQ_SW3_HS, 3, PMIC_IRQ_SW3_HS),
+	REGMAP_IRQ_REG(PF1550_PMIC_IRQ_LDO1_FAULT, 16, PMIC_IRQ_LDO1_FAULT),
+	REGMAP_IRQ_REG(PF1550_PMIC_IRQ_LDO2_FAULT, 16, PMIC_IRQ_LDO2_FAULT),
+	REGMAP_IRQ_REG(PF1550_PMIC_IRQ_LDO3_FAULT, 16, PMIC_IRQ_LDO3_FAULT),
+	REGMAP_IRQ_REG(PF1550_PMIC_IRQ_TEMP_110, 24, PMIC_IRQ_TEMP_110),
+	REGMAP_IRQ_REG(PF1550_PMIC_IRQ_TEMP_125, 24, PMIC_IRQ_TEMP_125),
+};
+
+static const struct regmap_irq_chip pf1550_regulator_irq_chip = {
+	.name = "pf1550-regulator",
+	.status_base = PF1550_PMIC_REG_SW_INT_STAT0,
+	.ack_base = PF1550_PMIC_REG_SW_INT_STAT0,
+	.mask_base = PF1550_PMIC_REG_SW_INT_MASK0,
+	.use_ack = 1,
+	.init_ack_masked = 1,
+	.num_regs = 25,
+	.irqs = pf1550_regulator_irqs,
+	.num_irqs = ARRAY_SIZE(pf1550_regulator_irqs),
+};
+
+static const struct resource regulator_resources[] = {
+	DEFINE_RES_IRQ(PF1550_PMIC_IRQ_SW1_LS),
+	DEFINE_RES_IRQ(PF1550_PMIC_IRQ_SW2_LS),
+	DEFINE_RES_IRQ(PF1550_PMIC_IRQ_SW3_LS),
+	DEFINE_RES_IRQ(PF1550_PMIC_IRQ_SW1_HS),
+	DEFINE_RES_IRQ(PF1550_PMIC_IRQ_SW2_HS),
+	DEFINE_RES_IRQ(PF1550_PMIC_IRQ_SW3_HS),
+	DEFINE_RES_IRQ(PF1550_PMIC_IRQ_LDO1_FAULT),
+	DEFINE_RES_IRQ(PF1550_PMIC_IRQ_LDO2_FAULT),
+	DEFINE_RES_IRQ(PF1550_PMIC_IRQ_LDO3_FAULT),
+	DEFINE_RES_IRQ(PF1550_PMIC_IRQ_TEMP_110),
+	DEFINE_RES_IRQ(PF1550_PMIC_IRQ_TEMP_125),
+};
+
+static const struct regmap_irq pf1550_onkey_irqs[] = {
+	REGMAP_IRQ_REG(PF1550_ONKEY_IRQ_PUSHI, 0, ONKEY_IRQ_PUSHI),
+	REGMAP_IRQ_REG(PF1550_ONKEY_IRQ_1SI, 0, ONKEY_IRQ_1SI),
+	REGMAP_IRQ_REG(PF1550_ONKEY_IRQ_2SI, 0, ONKEY_IRQ_2SI),
+	REGMAP_IRQ_REG(PF1550_ONKEY_IRQ_3SI, 0, ONKEY_IRQ_3SI),
+	REGMAP_IRQ_REG(PF1550_ONKEY_IRQ_4SI, 0, ONKEY_IRQ_4SI),
+	REGMAP_IRQ_REG(PF1550_ONKEY_IRQ_8SI, 0, ONKEY_IRQ_8SI),
+};
+
+static const struct regmap_irq_chip pf1550_onkey_irq_chip = {
+	.name = "pf1550-onkey",
+	.status_base = PF1550_PMIC_REG_ONKEY_INT_STAT0,
+	.ack_base = PF1550_PMIC_REG_ONKEY_INT_STAT0,
+	.mask_base = PF1550_PMIC_REG_ONKEY_INT_MASK0,
+	.use_ack = 1,
+	.init_ack_masked = 1,
+	.num_regs = 1,
+	.irqs = pf1550_onkey_irqs,
+	.num_irqs = ARRAY_SIZE(pf1550_onkey_irqs),
+};
+
+static const struct resource onkey_resources[] = {
+	DEFINE_RES_IRQ(PF1550_ONKEY_IRQ_PUSHI),
+	DEFINE_RES_IRQ(PF1550_ONKEY_IRQ_1SI),
+	DEFINE_RES_IRQ(PF1550_ONKEY_IRQ_2SI),
+	DEFINE_RES_IRQ(PF1550_ONKEY_IRQ_3SI),
+	DEFINE_RES_IRQ(PF1550_ONKEY_IRQ_4SI),
+	DEFINE_RES_IRQ(PF1550_ONKEY_IRQ_8SI),
+};
+
+static const struct regmap_irq pf1550_charger_irqs[] = {
+	REGMAP_IRQ_REG(PF1550_CHARG_IRQ_BAT2SOCI, 0, CHARG_IRQ_BAT2SOCI),
+	REGMAP_IRQ_REG(PF1550_CHARG_IRQ_BATI, 0, CHARG_IRQ_BATI),
+	REGMAP_IRQ_REG(PF1550_CHARG_IRQ_CHGI, 0, CHARG_IRQ_CHGI),
+	REGMAP_IRQ_REG(PF1550_CHARG_IRQ_VBUSI, 0, CHARG_IRQ_VBUSI),
+	REGMAP_IRQ_REG(PF1550_CHARG_IRQ_THMI, 0, CHARG_IRQ_THMI),
+};
+
+static const struct regmap_irq_chip pf1550_charger_irq_chip = {
+	.name = "pf1550-charger",
+	.status_base = PF1550_CHARG_REG_CHG_INT,
+	.ack_base = PF1550_CHARG_REG_CHG_INT,
+	.mask_base = PF1550_CHARG_REG_CHG_INT_MASK,
+	.use_ack = 1,
+	.init_ack_masked = 1,
+	.num_regs = 1,
+	.irqs = pf1550_charger_irqs,
+	.num_irqs = ARRAY_SIZE(pf1550_charger_irqs),
+};
+
+static const struct resource charger_resources[] = {
+	DEFINE_RES_IRQ(PF1550_CHARG_IRQ_BAT2SOCI),
+	DEFINE_RES_IRQ(PF1550_CHARG_IRQ_BATI),
+	DEFINE_RES_IRQ(PF1550_CHARG_IRQ_CHGI),
+	DEFINE_RES_IRQ(PF1550_CHARG_IRQ_VBUSI),
+	DEFINE_RES_IRQ(PF1550_CHARG_IRQ_THMI),
+};
+
+static const struct mfd_cell pf1550_regulator_cell = {
+	.name = "pf1550-regulator",
+	.num_resources = ARRAY_SIZE(regulator_resources),
+	.resources = regulator_resources,
+};
+
+static const struct mfd_cell pf1550_onkey_cell = {
+	.name = "pf1550-onkey",
+	.num_resources = ARRAY_SIZE(onkey_resources),
+	.resources = onkey_resources,
+};
+
+static const struct mfd_cell pf1550_charger_cell = {
+	.name = "pf1550-charger",
+	.num_resources = ARRAY_SIZE(charger_resources),
+	.resources = charger_resources,
+};
+
+/*
+ * The PF1550 is shipped in variants of A0, A1,...A9. Each variant defines a
+ * configuration of the PMIC in a One-Time Programmable (OTP) memory.
+ * This memory is accessed indirectly by writing valid keys to specific
+ * registers of the PMIC. To read the OTP memory after writing the valid keys,
+ * the OTP register address to be read is written to pf1550 register 0xc4 and
+ * its value read from pf1550 register 0xc5.
+ */
+static int pf1550_read_otp(const struct pf1550_ddata *pf1550, unsigned int index,
+			   unsigned int *val)
+{
+	int ret = 0;
+
+	ret = regmap_write(pf1550->regmap, PF1550_PMIC_REG_KEY, PF1550_OTP_PMIC_KEY);
+	if (ret)
+		goto read_err;
+
+	ret = regmap_write(pf1550->regmap, PF1550_CHARG_REG_CHGR_KEY2, PF1550_OTP_CHGR_KEY);
+	if (ret)
+		goto read_err;
+
+	ret = regmap_write(pf1550->regmap, PF1550_TEST_REG_KEY3, PF1550_OTP_TEST_KEY);
+	if (ret)
+		goto read_err;
+
+	ret = regmap_write(pf1550->regmap, PF1550_TEST_REG_FMRADDR, index);
+	if (ret)
+		goto read_err;
+
+	ret = regmap_read(pf1550->regmap, PF1550_TEST_REG_FMRDATA, val);
+	if (ret)
+		goto read_err;
+
+	return 0;
+
+read_err:
+	return dev_err_probe(pf1550->dev, ret, "OTP reg %x not found!\n", index);
+}
+
+static int pf1550_i2c_probe(struct i2c_client *i2c)
+{
+	const struct mfd_cell *regulator = &pf1550_regulator_cell;
+	const struct mfd_cell *charger = &pf1550_charger_cell;
+	const struct mfd_cell *onkey = &pf1550_onkey_cell;
+	unsigned int reg_data = 0, otp_data = 0;
+	struct pf1550_ddata *pf1550;
+	struct irq_domain *domain;
+	int irq, ret = 0;
+
+	pf1550 = devm_kzalloc(&i2c->dev, sizeof(*pf1550), GFP_KERNEL);
+	if (!pf1550)
+		return -ENOMEM;
+
+	i2c_set_clientdata(i2c, pf1550);
+	pf1550->dev = &i2c->dev;
+	pf1550->irq = i2c->irq;
+
+	pf1550->regmap = devm_regmap_init_i2c(i2c, &pf1550_regmap_config);
+	if (IS_ERR(pf1550->regmap))
+		return dev_err_probe(pf1550->dev, PTR_ERR(pf1550->regmap),
+				     "failed to allocate register map\n");
+
+	ret = regmap_read(pf1550->regmap, PF1550_PMIC_REG_DEVICE_ID, &reg_data);
+	if (ret < 0)
+		return dev_err_probe(pf1550->dev, ret, "cannot read chip ID\n");
+	if (reg_data != PF1550_DEVICE_ID)
+		return dev_err_probe(pf1550->dev, -ENODEV, "invalid device ID: 0x%02x\n", reg_data);
+
+	/* Regulator DVS for SW2 */
+	ret = pf1550_read_otp(pf1550, PF1550_OTP_SW2_SW3, &otp_data);
+	if (ret)
+		return ret;
+
+	/* When clear, DVS should be enabled */
+	if (!(otp_data & OTP_SW2_DVS_ENB))
+		pf1550->dvs2_enable = true;
+
+	/* Regulator DVS for SW1 */
+	ret = pf1550_read_otp(pf1550, PF1550_OTP_SW1_SW2, &otp_data);
+	if (ret)
+		return ret;
+
+	if (!(otp_data & OTP_SW1_DVS_ENB))
+		pf1550->dvs1_enable = true;
+
+	/* Add top level interrupts */
+	ret = devm_regmap_add_irq_chip(pf1550->dev, pf1550->regmap, pf1550->irq,
+				       IRQF_ONESHOT | IRQF_SHARED |
+				       IRQF_TRIGGER_FALLING,
+				       0, &pf1550_irq_chip,
+				       &pf1550->irq_data);
+	if (ret)
+		return ret;
+
+	/* Add regulator */
+	irq = regmap_irq_get_virq(pf1550->irq_data, PF1550_IRQ_REGULATOR);
+	if (irq < 0)
+		return dev_err_probe(pf1550->dev, irq,
+				     "Failed to get parent vIRQ(%d) for chip %s\n",
+				     PF1550_IRQ_REGULATOR, pf1550_irq_chip.name);
+
+	ret = devm_regmap_add_irq_chip(pf1550->dev, pf1550->regmap, irq,
+				       IRQF_ONESHOT | IRQF_SHARED |
+				       IRQF_TRIGGER_FALLING, 0,
+				       &pf1550_regulator_irq_chip,
+				       &pf1550->irq_data_regulator);
+	if (ret)
+		return dev_err_probe(pf1550->dev, ret, "Failed to add %s IRQ chip\n",
+				     pf1550_regulator_irq_chip.name);
+
+	domain = regmap_irq_get_domain(pf1550->irq_data_regulator);
+
+	ret = devm_mfd_add_devices(pf1550->dev, PLATFORM_DEVID_NONE, regulator, 1, NULL, 0, domain);
+	if (ret)
+		return ret;
+
+	/* Add onkey */
+	irq = regmap_irq_get_virq(pf1550->irq_data, PF1550_IRQ_ONKEY);
+	if (irq < 0)
+		return dev_err_probe(pf1550->dev, irq,
+				     "Failed to get parent vIRQ(%d) for chip %s\n",
+				     PF1550_IRQ_ONKEY, pf1550_irq_chip.name);
+
+	ret = devm_regmap_add_irq_chip(pf1550->dev, pf1550->regmap, irq,
+				       IRQF_ONESHOT | IRQF_SHARED |
+				       IRQF_TRIGGER_FALLING, 0,
+				       &pf1550_onkey_irq_chip,
+				       &pf1550->irq_data_onkey);
+	if (ret)
+		return dev_err_probe(pf1550->dev, ret, "Failed to add %s IRQ chip\n",
+				     pf1550_onkey_irq_chip.name);
+
+	domain = regmap_irq_get_domain(pf1550->irq_data_onkey);
+
+	ret = devm_mfd_add_devices(pf1550->dev, PLATFORM_DEVID_NONE, onkey, 1, NULL, 0, domain);
+	if (ret)
+		return ret;
+
+	/* Add battery charger */
+	irq = regmap_irq_get_virq(pf1550->irq_data, PF1550_IRQ_CHG);
+	if (irq < 0)
+		return dev_err_probe(pf1550->dev, irq,
+				     "Failed to get parent vIRQ(%d) for chip %s\n",
+				     PF1550_IRQ_CHG, pf1550_irq_chip.name);
+
+	ret = devm_regmap_add_irq_chip(pf1550->dev, pf1550->regmap, irq,
+				       IRQF_ONESHOT | IRQF_SHARED |
+				       IRQF_TRIGGER_FALLING, 0,
+				       &pf1550_charger_irq_chip,
+				       &pf1550->irq_data_charger);
+	if (ret)
+		return dev_err_probe(pf1550->dev, ret, "Failed to add %s IRQ chip\n",
+				     pf1550_charger_irq_chip.name);
+
+	domain = regmap_irq_get_domain(pf1550->irq_data_charger);
+
+	return devm_mfd_add_devices(pf1550->dev, PLATFORM_DEVID_NONE, charger, 1, NULL, 0, domain);
+}
+
+static int pf1550_suspend(struct device *dev)
+{
+	struct pf1550_ddata *pf1550 = dev_get_drvdata(dev);
+
+	if (device_may_wakeup(dev)) {
+		enable_irq_wake(pf1550->irq);
+		disable_irq(pf1550->irq);
+	}
+
+	return 0;
+}
+
+static int pf1550_resume(struct device *dev)
+{
+	struct pf1550_ddata *pf1550 = dev_get_drvdata(dev);
+
+	if (device_may_wakeup(dev)) {
+		disable_irq_wake(pf1550->irq);
+		enable_irq(pf1550->irq);
+	}
+
+	return 0;
+}
+static DEFINE_SIMPLE_DEV_PM_OPS(pf1550_pm, pf1550_suspend, pf1550_resume);
+
+static const struct i2c_device_id pf1550_i2c_id[] = {
+	{ "pf1550" },
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(i2c, pf1550_i2c_id);
+
+static const struct of_device_id pf1550_dt_match[] = {
+	{ .compatible = "nxp,pf1550" },
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, pf1550_dt_match);
+
+static struct i2c_driver pf1550_i2c_driver = {
+	.driver = {
+		   .name = "pf1550",
+		   .pm = pm_sleep_ptr(&pf1550_pm),
+		   .of_match_table = pf1550_dt_match,
+	},
+	.probe = pf1550_i2c_probe,
+	.id_table = pf1550_i2c_id,
+};
+module_i2c_driver(pf1550_i2c_driver);
+
+MODULE_DESCRIPTION("NXP PF1550 core driver");
+MODULE_AUTHOR("Robin Gong <yibin.gong@freescale.com>");
+MODULE_LICENSE("GPL");