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, 144 insertions, 0 deletions

diff --git a/sound/soc/codecs/wcd-common.c b/sound/soc/codecs/wcd-common.c
new file mode 100644
index 000000000..9016e9745
--- /dev/null
+++ b/sound/soc/codecs/wcd-common.c
@@ -0,0 +1,144 @@
+// SPDX-License-Identifier: GPL-2.0-only
+// Copyright (c) 2025, Qualcomm Technologies, Inc. and/or its subsidiaries.
+
+#include <linux/export.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/device.h>
+#include <linux/of.h>
+#include <linux/printk.h>
+#include <linux/component.h>
+#include <linux/pm_runtime.h>
+#include <linux/soundwire/sdw.h>
+#include <linux/soundwire/sdw_type.h>
+#include <linux/regmap.h>
+
+#include "wcd-common.h"
+
+#define WCD_MIN_MICBIAS_MV	1000
+#define WCD_DEF_MICBIAS_MV	1800
+#define WCD_MAX_MICBIAS_MV	2850
+
+#define SWRS_SCP_HOST_CLK_DIV2_CTL_BANK(m) (0xE0 + 0x10 * (m))
+
+int wcd_get_micb_vout_ctl_val(struct device *dev, u32 micb_mv)
+{
+	/* min micbias voltage is 1V and maximum is 2.85V */
+	if (micb_mv < WCD_MIN_MICBIAS_MV || micb_mv > WCD_MAX_MICBIAS_MV) {
+		dev_err(dev, "Unsupported micbias voltage (%u mV)\n", micb_mv);
+		return -EINVAL;
+	}
+
+	return (micb_mv - WCD_MIN_MICBIAS_MV) / 50;
+}
+EXPORT_SYMBOL_GPL(wcd_get_micb_vout_ctl_val);
+
+static int wcd_get_micbias_val(struct device *dev, int micb_num, u32 *micb_mv)
+{
+	char micbias[64];
+	int mv;
+
+	sprintf(micbias, "qcom,micbias%d-microvolt", micb_num);
+
+	if (of_property_read_u32(dev->of_node, micbias, &mv)) {
+		dev_err(dev, "%s value not found, using default\n", micbias);
+		mv = WCD_DEF_MICBIAS_MV;
+	} else {
+		/* convert it to milli volts */
+		mv = mv/1000;
+	}
+	if (micb_mv)
+		*micb_mv = mv;
+
+	mv = wcd_get_micb_vout_ctl_val(dev, mv);
+	if (mv < 0) {
+		dev_err(dev, "Unsupported %s voltage (%d mV), falling back to default (%d mV)\n",
+				micbias, mv, WCD_DEF_MICBIAS_MV);
+		return wcd_get_micb_vout_ctl_val(dev, WCD_DEF_MICBIAS_MV);
+	}
+
+	return mv;
+}
+
+int wcd_dt_parse_micbias_info(struct wcd_common *common)
+{
+	int ret, i;
+
+	for (i = 0; i < common->max_bias; i++) {
+		ret = wcd_get_micbias_val(common->dev, i + 1, &common->micb_mv[i]);
+		if (ret < 0)
+			return ret;
+		common->micb_vout[i] = ret;
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(wcd_dt_parse_micbias_info);
+
+static int wcd_sdw_component_bind(struct device *dev, struct device *master, void *data)
+{
+	pm_runtime_set_autosuspend_delay(dev, 3000);
+	pm_runtime_use_autosuspend(dev);
+	pm_runtime_mark_last_busy(dev);
+	pm_runtime_set_active(dev);
+	pm_runtime_enable(dev);
+
+	return 0;
+}
+
+static void wcd_sdw_component_unbind(struct device *dev, struct device *master, void *data)
+{
+	pm_runtime_disable(dev);
+	pm_runtime_set_suspended(dev);
+	pm_runtime_dont_use_autosuspend(dev);
+}
+
+const struct component_ops wcd_sdw_component_ops = {
+	.bind = wcd_sdw_component_bind,
+	.unbind = wcd_sdw_component_unbind,
+};
+EXPORT_SYMBOL_GPL(wcd_sdw_component_ops);
+
+int wcd_update_status(struct sdw_slave *slave, enum sdw_slave_status status)
+{
+	struct regmap *regmap = dev_get_regmap(&slave->dev, NULL);
+
+	if (regmap && status == SDW_SLAVE_ATTACHED) {
+		/* Write out any cached changes that happened between probe and attach */
+		regcache_cache_only(regmap, false);
+		return regcache_sync(regmap);
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(wcd_update_status);
+
+int wcd_bus_config(struct sdw_slave *slave, struct sdw_bus_params *params)
+{
+	sdw_write(slave, SWRS_SCP_HOST_CLK_DIV2_CTL_BANK(params->next_bank), 0x01);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(wcd_bus_config);
+
+int wcd_interrupt_callback(struct sdw_slave *slave, struct irq_domain *slave_irq,
+		unsigned int wcd_intr_status0, unsigned int wcd_intr_status1,
+		unsigned int wcd_intr_status2)
+{
+	struct regmap *regmap = dev_get_regmap(&slave->dev, NULL);
+	u32 sts1, sts2, sts3;
+
+	do {
+		handle_nested_irq(irq_find_mapping(slave_irq, 0));
+		regmap_read(regmap, wcd_intr_status0, &sts1);
+		regmap_read(regmap, wcd_intr_status1, &sts2);
+		regmap_read(regmap, wcd_intr_status2, &sts3);
+
+	} while (sts1 || sts2 || sts3);
+
+	return IRQ_HANDLED;
+}
+EXPORT_SYMBOL_GPL(wcd_interrupt_callback);
+
+MODULE_DESCRIPTION("Common Qualcomm WCD Codec helpers driver");
+MODULE_LICENSE("GPL");