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, 551 insertions, 0 deletions

diff --git a/drivers/usb/cdns3/drd.c b/drivers/usb/cdns3/drd.c
new file mode 100644
index 000000000..d2bb682e4
--- /dev/null
+++ b/drivers/usb/cdns3/drd.c
@@ -0,0 +1,551 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Cadence USBSS and USBSSP DRD Driver.
+ *
+ * Copyright (C) 2018-2020 Cadence.
+ * Copyright (C) 2019 Texas Instruments
+ *
+ * Author: Pawel Laszczak <pawell@cadence.com>
+ *         Roger Quadros <rogerq@ti.com>
+ *
+ */
+#include <linux/kernel.h>
+#include <linux/interrupt.h>
+#include <linux/delay.h>
+#include <linux/iopoll.h>
+#include <linux/usb/otg.h>
+
+#include "drd.h"
+#include "core.h"
+
+/**
+ * cdns_set_mode - change mode of OTG Core
+ * @cdns: pointer to context structure
+ * @mode: selected mode from cdns_role
+ *
+ * Returns 0 on success otherwise negative errno
+ */
+static int cdns_set_mode(struct cdns *cdns, enum usb_dr_mode mode)
+{
+	void __iomem  *override_reg;
+	u32 reg;
+
+	switch (mode) {
+	case USB_DR_MODE_PERIPHERAL:
+		break;
+	case USB_DR_MODE_HOST:
+		break;
+	case USB_DR_MODE_OTG:
+		dev_dbg(cdns->dev, "Set controller to OTG mode\n");
+
+		if (cdns->version == CDNSP_CONTROLLER_V2)
+			override_reg = &cdns->otg_cdnsp_regs->override;
+		else if (cdns->version == CDNS3_CONTROLLER_V1)
+			override_reg = &cdns->otg_v1_regs->override;
+		else
+			override_reg = &cdns->otg_v0_regs->ctrl1;
+
+		reg = readl(override_reg);
+
+		if (cdns->version != CDNS3_CONTROLLER_V0)
+			reg |= OVERRIDE_IDPULLUP;
+		else
+			reg |= OVERRIDE_IDPULLUP_V0;
+
+		writel(reg, override_reg);
+
+		if (cdns->version == CDNS3_CONTROLLER_V1) {
+			/*
+			 * Enable work around feature built into the
+			 * controller to address issue with RX Sensitivity
+			 * est (EL_17) for USB2 PHY. The issue only occures
+			 * for 0x0002450D controller version.
+			 */
+			if (cdns->phyrst_a_enable) {
+				reg = readl(&cdns->otg_v1_regs->phyrst_cfg);
+				reg |= PHYRST_CFG_PHYRST_A_ENABLE;
+				writel(reg, &cdns->otg_v1_regs->phyrst_cfg);
+			}
+		}
+
+		/*
+		 * Hardware specification says: "ID_VALUE must be valid within
+		 * 50ms after idpullup is set to '1" so driver must wait
+		 * 50ms before reading this pin.
+		 */
+		usleep_range(50000, 60000);
+		break;
+	default:
+		dev_err(cdns->dev, "Unsupported mode of operation %d\n", mode);
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+int cdns_get_id(struct cdns *cdns)
+{
+	int id;
+
+	if (cdns->no_drd)
+		return 0;
+
+	id = readl(&cdns->otg_regs->sts) & OTGSTS_ID_VALUE;
+	dev_dbg(cdns->dev, "OTG ID: %d", id);
+
+	return id;
+}
+
+int cdns_get_vbus(struct cdns *cdns)
+{
+	int vbus;
+
+	vbus = !!(readl(&cdns->otg_regs->sts) & OTGSTS_VBUS_VALID);
+	dev_dbg(cdns->dev, "OTG VBUS: %d", vbus);
+
+	return vbus;
+}
+
+void cdns_clear_vbus(struct cdns *cdns)
+{
+	u32 reg;
+
+	if (cdns->version != CDNSP_CONTROLLER_V2 || cdns->no_drd)
+		return;
+
+	reg = readl(&cdns->otg_cdnsp_regs->override);
+	reg |= OVERRIDE_SESS_VLD_SEL;
+	writel(reg, &cdns->otg_cdnsp_regs->override);
+}
+EXPORT_SYMBOL_GPL(cdns_clear_vbus);
+
+void cdns_set_vbus(struct cdns *cdns)
+{
+	u32 reg;
+
+	if (cdns->version != CDNSP_CONTROLLER_V2 || cdns->no_drd)
+		return;
+
+	reg = readl(&cdns->otg_cdnsp_regs->override);
+	reg &= ~OVERRIDE_SESS_VLD_SEL;
+	writel(reg, &cdns->otg_cdnsp_regs->override);
+}
+EXPORT_SYMBOL_GPL(cdns_set_vbus);
+
+bool cdns_is_host(struct cdns *cdns)
+{
+	if (cdns->dr_mode == USB_DR_MODE_HOST)
+		return true;
+	else if (cdns_get_id(cdns) == CDNS3_ID_HOST)
+		return true;
+
+	return false;
+}
+
+bool cdns_is_device(struct cdns *cdns)
+{
+	if (cdns->dr_mode == USB_DR_MODE_PERIPHERAL)
+		return true;
+	else if (cdns->dr_mode == USB_DR_MODE_OTG)
+		if (cdns_get_id(cdns) == CDNS3_ID_PERIPHERAL)
+			return true;
+
+	return false;
+}
+
+/**
+ * cdns_otg_disable_irq - Disable all OTG interrupts
+ * @cdns: Pointer to controller context structure
+ */
+static void cdns_otg_disable_irq(struct cdns *cdns)
+{
+	if (cdns->version)
+		writel(0, &cdns->otg_irq_regs->ien);
+}
+
+/**
+ * cdns_otg_enable_irq - enable id and sess_valid interrupts
+ * @cdns: Pointer to controller context structure
+ */
+static void cdns_otg_enable_irq(struct cdns *cdns)
+{
+	writel(OTGIEN_ID_CHANGE_INT | OTGIEN_VBUSVALID_RISE_INT |
+	       OTGIEN_VBUSVALID_FALL_INT, &cdns->otg_irq_regs->ien);
+}
+
+/**
+ * cdns_drd_host_on - start host.
+ * @cdns: Pointer to controller context structure.
+ *
+ * Returns 0 on success otherwise negative errno.
+ */
+int cdns_drd_host_on(struct cdns *cdns)
+{
+	u32 val, ready_bit;
+	int ret = 0;
+
+	if (cdns->no_drd)
+		goto phy_set;
+
+	/* Enable host mode. */
+	writel(OTGCMD_HOST_BUS_REQ | OTGCMD_OTG_DIS,
+	       &cdns->otg_regs->cmd);
+
+	if (cdns->version == CDNSP_CONTROLLER_V2)
+		ready_bit = OTGSTS_CDNSP_XHCI_READY;
+	else
+		ready_bit = OTGSTS_CDNS3_XHCI_READY;
+
+	dev_dbg(cdns->dev, "Waiting till Host mode is turned on\n");
+	ret = readl_poll_timeout_atomic(&cdns->otg_regs->sts, val,
+					val & ready_bit, 1, 100000);
+
+	if (ret)
+		dev_err(cdns->dev, "timeout waiting for xhci_ready\n");
+
+phy_set:
+	phy_set_mode(cdns->usb2_phy, PHY_MODE_USB_HOST);
+	phy_set_mode(cdns->usb3_phy, PHY_MODE_USB_HOST);
+	return ret;
+}
+
+/**
+ * cdns_drd_host_off - stop host.
+ * @cdns: Pointer to controller context structure.
+ */
+void cdns_drd_host_off(struct cdns *cdns)
+{
+	u32 val;
+
+	if (cdns->no_drd)
+		goto phy_set;
+
+	writel(OTGCMD_HOST_BUS_DROP | OTGCMD_DEV_BUS_DROP |
+	       OTGCMD_DEV_POWER_OFF | OTGCMD_HOST_POWER_OFF,
+	       &cdns->otg_regs->cmd);
+
+	/* Waiting till H_IDLE state.*/
+	readl_poll_timeout_atomic(&cdns->otg_regs->state, val,
+				  !(val & OTGSTATE_HOST_STATE_MASK),
+				  1, 2000000);
+
+phy_set:
+	phy_set_mode(cdns->usb2_phy, PHY_MODE_INVALID);
+	phy_set_mode(cdns->usb3_phy, PHY_MODE_INVALID);
+}
+
+/**
+ * cdns_drd_gadget_on - start gadget.
+ * @cdns: Pointer to controller context structure.
+ *
+ * Returns 0 on success otherwise negative errno
+ */
+int cdns_drd_gadget_on(struct cdns *cdns)
+{
+	u32 reg = OTGCMD_OTG_DIS;
+	u32 ready_bit;
+	int ret, val;
+
+	if (cdns->no_drd)
+		goto phy_set;
+
+	/* switch OTG core */
+	writel(OTGCMD_DEV_BUS_REQ | reg, &cdns->otg_regs->cmd);
+
+	dev_dbg(cdns->dev, "Waiting till Device mode is turned on\n");
+
+	if (cdns->version == CDNSP_CONTROLLER_V2)
+		ready_bit = OTGSTS_CDNSP_DEV_READY;
+	else
+		ready_bit = OTGSTS_CDNS3_DEV_READY;
+
+	ret = readl_poll_timeout_atomic(&cdns->otg_regs->sts, val,
+					val & ready_bit, 1, 100000);
+	if (ret) {
+		dev_err(cdns->dev, "timeout waiting for dev_ready\n");
+		return ret;
+	}
+
+phy_set:
+	phy_set_mode(cdns->usb2_phy, PHY_MODE_USB_DEVICE);
+	phy_set_mode(cdns->usb3_phy, PHY_MODE_USB_DEVICE);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(cdns_drd_gadget_on);
+
+/**
+ * cdns_drd_gadget_off - stop gadget.
+ * @cdns: Pointer to controller context structure.
+ */
+void cdns_drd_gadget_off(struct cdns *cdns)
+{
+	u32 val;
+
+	if (cdns->no_drd)
+		goto phy_set;
+
+	/*
+	 * Driver should wait at least 10us after disabling Device
+	 * before turning-off Device (DEV_BUS_DROP).
+	 */
+	usleep_range(20, 30);
+	writel(OTGCMD_HOST_BUS_DROP | OTGCMD_DEV_BUS_DROP |
+	       OTGCMD_DEV_POWER_OFF | OTGCMD_HOST_POWER_OFF,
+	       &cdns->otg_regs->cmd);
+	/* Waiting till DEV_IDLE state.*/
+	readl_poll_timeout_atomic(&cdns->otg_regs->state, val,
+				  !(val & OTGSTATE_DEV_STATE_MASK),
+				  1, 2000000);
+
+phy_set:
+	phy_set_mode(cdns->usb2_phy, PHY_MODE_INVALID);
+	phy_set_mode(cdns->usb3_phy, PHY_MODE_INVALID);
+}
+EXPORT_SYMBOL_GPL(cdns_drd_gadget_off);
+
+/**
+ * cdns_init_otg_mode - initialize drd controller
+ * @cdns: Pointer to controller context structure
+ *
+ * Returns 0 on success otherwise negative errno
+ */
+static int cdns_init_otg_mode(struct cdns *cdns)
+{
+	int ret;
+
+	cdns_otg_disable_irq(cdns);
+	/* clear all interrupts */
+	writel(~0, &cdns->otg_irq_regs->ivect);
+
+	ret = cdns_set_mode(cdns, USB_DR_MODE_OTG);
+	if (ret)
+		return ret;
+
+	cdns_otg_enable_irq(cdns);
+
+	return 0;
+}
+
+/**
+ * cdns_drd_update_mode - initialize mode of operation
+ * @cdns: Pointer to controller context structure
+ *
+ * Returns 0 on success otherwise negative errno
+ */
+int cdns_drd_update_mode(struct cdns *cdns)
+{
+	int ret;
+
+	switch (cdns->dr_mode) {
+	case USB_DR_MODE_PERIPHERAL:
+		ret = cdns_set_mode(cdns, USB_DR_MODE_PERIPHERAL);
+		break;
+	case USB_DR_MODE_HOST:
+		ret = cdns_set_mode(cdns, USB_DR_MODE_HOST);
+		break;
+	case USB_DR_MODE_OTG:
+		ret = cdns_init_otg_mode(cdns);
+		break;
+	default:
+		dev_err(cdns->dev, "Unsupported mode of operation %d\n",
+			cdns->dr_mode);
+		return -EINVAL;
+	}
+
+	return ret;
+}
+
+static irqreturn_t cdns_drd_thread_irq(int irq, void *data)
+{
+	struct cdns *cdns = data;
+
+	cdns_hw_role_switch(cdns);
+
+	return IRQ_HANDLED;
+}
+
+/**
+ * cdns_drd_irq - interrupt handler for OTG events
+ *
+ * @irq: irq number for cdns core device
+ * @data: structure of cdns
+ *
+ * Returns IRQ_HANDLED or IRQ_NONE
+ */
+static irqreturn_t cdns_drd_irq(int irq, void *data)
+{
+	irqreturn_t ret = IRQ_NONE;
+	struct cdns *cdns = data;
+	u32 reg;
+
+	if (cdns->dr_mode != USB_DR_MODE_OTG)
+		return IRQ_NONE;
+
+	if (cdns->in_lpm)
+		return ret;
+
+	reg = readl(&cdns->otg_irq_regs->ivect);
+
+	if (!reg)
+		return IRQ_NONE;
+
+	if (reg & OTGIEN_ID_CHANGE_INT) {
+		dev_dbg(cdns->dev, "OTG IRQ: new ID: %d\n",
+			cdns_get_id(cdns));
+
+		ret = IRQ_WAKE_THREAD;
+	}
+
+	if (reg & (OTGIEN_VBUSVALID_RISE_INT | OTGIEN_VBUSVALID_FALL_INT)) {
+		dev_dbg(cdns->dev, "OTG IRQ: new VBUS: %d\n",
+			cdns_get_vbus(cdns));
+
+		ret = IRQ_WAKE_THREAD;
+	}
+
+	writel(~0, &cdns->otg_irq_regs->ivect);
+	return ret;
+}
+
+int cdns_drd_init(struct cdns *cdns)
+{
+	void __iomem *regs;
+	u32 state, reg;
+	int ret;
+
+	if (cdns->no_drd) {
+		cdns->dr_mode = usb_get_dr_mode(cdns->dev);
+
+		if (cdns->dr_mode != USB_DR_MODE_HOST &&
+		    cdns->dr_mode != USB_DR_MODE_PERIPHERAL) {
+			dev_err(cdns->dev, "Incorrect dr_mode\n");
+			return -EINVAL;
+		}
+
+		return 0;
+	}
+
+	regs = devm_ioremap_resource(cdns->dev, &cdns->otg_res);
+	if (IS_ERR(regs))
+		return PTR_ERR(regs);
+
+	/* Detection of DRD version. Controller has been released
+	 * in three versions. All are very similar and are software compatible,
+	 * but they have same changes in register maps.
+	 * The first register in oldest version is command register and it's
+	 * read only. Driver should read 0 from it. On the other hand, in v1
+	 * and v2 the first register contains device ID number which is not
+	 * set to 0. Driver uses this fact to detect the proper version of
+	 * controller.
+	 */
+	cdns->otg_v0_regs = regs;
+	if (!readl(&cdns->otg_v0_regs->cmd)) {
+		cdns->version  = CDNS3_CONTROLLER_V0;
+		cdns->otg_v1_regs = NULL;
+		cdns->otg_cdnsp_regs = NULL;
+		cdns->otg_regs = regs;
+		cdns->otg_irq_regs = (struct cdns_otg_irq_regs __iomem  *)
+				     &cdns->otg_v0_regs->ien;
+		writel(1, &cdns->otg_v0_regs->simulate);
+		dev_dbg(cdns->dev, "DRD version v0 (%08x)\n",
+			 readl(&cdns->otg_v0_regs->version));
+	} else {
+		cdns->otg_v0_regs = NULL;
+		cdns->otg_v1_regs = regs;
+		cdns->otg_cdnsp_regs = regs;
+
+		cdns->otg_regs = (void __iomem *)&cdns->otg_v1_regs->cmd;
+
+		state = readl(&cdns->otg_cdnsp_regs->did);
+
+		if (OTG_CDNSP_CHECK_DID(state)) {
+			cdns->otg_irq_regs = (struct cdns_otg_irq_regs __iomem *)
+					      &cdns->otg_cdnsp_regs->ien;
+			cdns->version  = CDNSP_CONTROLLER_V2;
+		} else if (OTG_CDNS3_CHECK_DID(state)) {
+			cdns->otg_irq_regs = (struct cdns_otg_irq_regs __iomem *)
+					      &cdns->otg_v1_regs->ien;
+			writel(1, &cdns->otg_v1_regs->simulate);
+
+			if (cdns->pdata &&
+			    (cdns->pdata->quirks & CDNS3_DRD_SUSPEND_RESIDENCY_ENABLE)) {
+				reg = readl(&cdns->otg_v1_regs->susp_ctrl);
+				reg |= SUSP_CTRL_SUSPEND_RESIDENCY_ENABLE;
+				writel(reg, &cdns->otg_v1_regs->susp_ctrl);
+			}
+
+			cdns->version  = CDNS3_CONTROLLER_V1;
+		} else {
+			dev_err(cdns->dev, "not supported DID=0x%08x\n", state);
+			return -EINVAL;
+		}
+
+		dev_dbg(cdns->dev, "DRD version v1 (ID: %08x, rev: %08x)\n",
+			 readl(&cdns->otg_v1_regs->did),
+			 readl(&cdns->otg_v1_regs->rid));
+	}
+
+	state = OTGSTS_STRAP(readl(&cdns->otg_regs->sts));
+
+	/* Update dr_mode according to STRAP configuration. */
+	cdns->dr_mode = USB_DR_MODE_OTG;
+
+	if ((cdns->version == CDNSP_CONTROLLER_V2 &&
+	     state == OTGSTS_CDNSP_STRAP_HOST) ||
+	    (cdns->version != CDNSP_CONTROLLER_V2 &&
+	     state == OTGSTS_STRAP_HOST)) {
+		dev_dbg(cdns->dev, "Controller strapped to HOST\n");
+		cdns->dr_mode = USB_DR_MODE_HOST;
+	} else if ((cdns->version == CDNSP_CONTROLLER_V2 &&
+		    state == OTGSTS_CDNSP_STRAP_GADGET) ||
+		   (cdns->version != CDNSP_CONTROLLER_V2 &&
+		    state == OTGSTS_STRAP_GADGET)) {
+		dev_dbg(cdns->dev, "Controller strapped to PERIPHERAL\n");
+		cdns->dr_mode = USB_DR_MODE_PERIPHERAL;
+	}
+
+	ret = devm_request_threaded_irq(cdns->dev, cdns->otg_irq,
+					cdns_drd_irq,
+					cdns_drd_thread_irq,
+					IRQF_SHARED,
+					dev_name(cdns->dev), cdns);
+	if (ret) {
+		dev_err(cdns->dev, "couldn't get otg_irq\n");
+		return ret;
+	}
+
+	state = readl(&cdns->otg_regs->sts);
+	if (OTGSTS_OTG_NRDY(state)) {
+		dev_err(cdns->dev, "Cadence USB3 OTG device not ready\n");
+		return -ENODEV;
+	}
+
+	return 0;
+}
+
+int cdns_drd_exit(struct cdns *cdns)
+{
+	if (cdns->no_drd)
+		return 0;
+
+	cdns_otg_disable_irq(cdns);
+
+	return 0;
+}
+
+/* Indicate the cdns3 core was power lost before */
+bool cdns_power_is_lost(struct cdns *cdns)
+{
+	if (cdns->no_drd)
+		return false;
+
+	if (cdns->version == CDNS3_CONTROLLER_V0) {
+		if (!(readl(&cdns->otg_v0_regs->simulate) & BIT(0)))
+			return true;
+	} else {
+		if (!(readl(&cdns->otg_v1_regs->simulate) & BIT(0)))
+			return true;
+	}
+	return false;
+}
+EXPORT_SYMBOL_GPL(cdns_power_is_lost);