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, 735 insertions, 0 deletions

diff --git a/drivers/rtc/rtc-optee.c b/drivers/rtc/rtc-optee.c
new file mode 100644
index 000000000..6c908c0d8
--- /dev/null
+++ b/drivers/rtc/rtc-optee.c
@@ -0,0 +1,735 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2022 Microchip.
+ */
+
+#include <linux/device.h>
+#include <linux/kernel.h>
+#include <linux/kthread.h>
+#include <linux/module.h>
+#include <linux/rtc.h>
+#include <linux/tee_drv.h>
+
+#define RTC_INFO_VERSION			0x1
+
+#define TA_RTC_FEATURE_CORRECTION		BIT(0)
+#define TA_RTC_FEATURE_ALARM			BIT(1)
+#define TA_RTC_FEATURE_WAKEUP_ALARM		BIT(2)
+
+enum rtc_optee_pta_cmd {
+	/*  PTA_CMD_RTC_GET_INFO - Get RTC information
+	 *
+	 * [out]        memref[0]  RTC buffer memory reference containing a struct pta_rtc_info
+	 */
+	PTA_CMD_RTC_GET_INF = 0x0,
+
+	/*
+	 * PTA_CMD_RTC_GET_TIME - Get time from RTC
+	 *
+	 * [out]    memref[0]  RTC buffer memory reference containing a struct pta_rtc_time
+	 */
+	PTA_CMD_RTC_GET_TIME = 0x1,
+
+	/*
+	 * PTA_CMD_RTC_SET_TIME - Set time from RTC
+	 *
+	 * [in]     memref[0]  RTC buffer memory reference containing a struct pta_rtc_time to be
+	 *                     used as RTC time
+	 */
+	PTA_CMD_RTC_SET_TIME = 0x2,
+
+	/*
+	 * PTA_CMD_RTC_GET_OFFSET - Get RTC offset
+	 *
+	 * [out]    value[0].a  RTC offset (signed 32bit value)
+	 */
+	PTA_CMD_RTC_GET_OFFSET = 0x3,
+
+	/*
+	 * PTA_CMD_RTC_SET_OFFSET - Set RTC offset
+	 *
+	 * [in]     value[0].a  RTC offset to be set (signed 32bit value)
+	 */
+	PTA_CMD_RTC_SET_OFFSET = 0x4,
+
+	/*
+	 * PTA_CMD_RTC_READ_ALARM - Read RTC alarm
+	 *
+	 * [out]     memref[0]  RTC buffer memory reference containing a struct pta_rtc_alarm
+	 */
+	PTA_CMD_RTC_READ_ALARM = 0x5,
+
+	/*
+	 * PTA_CMD_RTC_SET_ALARM - Set RTC alarm
+	 *
+	 * [in]     memref[0]  RTC buffer memory reference containing a struct pta_rtc_alarm to be
+	 *                     used as RTC alarm
+	 */
+	PTA_CMD_RTC_SET_ALARM = 0x6,
+
+	/*
+	 * PTA_CMD_RTC_ENABLE_ALARM - Enable Alarm
+	 *
+	 * [in]     value[0].a  RTC IRQ flag (uint32_t), 0 to disable the alarm, 1 to enable
+	 */
+	PTA_CMD_RTC_ENABLE_ALARM = 0x7,
+
+	/*
+	 * PTA_CMD_RTC_WAIT_ALARM - Get alarm event
+	 *
+	 * [out]     value[0].a  RTC wait alarm return status (uint32_t):
+	 *                       - 0: No alarm event
+	 *                       - 1: Alarm event occurred
+	 *                       - 2: Alarm event canceled
+	 */
+	PTA_CMD_RTC_WAIT_ALARM = 0x8,
+
+	/*
+	 * PTA_CMD_RTC_CANCEL_WAIT - Cancel wait for alarm event
+	 */
+	PTA_CMD_RTC_CANCEL_WAIT = 0x9,
+
+	/*
+	 * PTA_CMD_RTC_SET_WAKE_ALARM_STATUS - Set RTC wake alarm status flag
+	 *
+	 * [in]     value[0].a RTC IRQ wake alarm flag (uint32_t), 0 to disable the wake up
+	 *                     capability, 1 to enable.
+	 */
+	PTA_CMD_RTC_SET_WAKE_ALARM_STATUS = 0xA,
+};
+
+enum rtc_wait_alarm_status {
+	WAIT_ALARM_RESET = 0x0,
+	WAIT_ALARM_ALARM_OCCURRED = 0x1,
+	WAIT_ALARM_CANCELED = 0x2,
+};
+
+struct optee_rtc_time {
+	u32 tm_sec;
+	u32 tm_min;
+	u32 tm_hour;
+	u32 tm_mday;
+	u32 tm_mon;
+	u32 tm_year;
+	u32 tm_wday;
+};
+
+struct optee_rtc_alarm {
+	u8 enabled;
+	u8 pending;
+	struct optee_rtc_time time;
+};
+
+struct optee_rtc_info {
+	u64 version;
+	u64 features;
+	struct optee_rtc_time range_min;
+	struct optee_rtc_time range_max;
+};
+
+/**
+ * struct optee_rtc - OP-TEE RTC private data
+ * @dev:		OP-TEE based RTC device.
+ * @ctx:		OP-TEE context handler.
+ * @session_id:		RTC TA session identifier.
+ * @session2_id:	RTC wait alarm session identifier.
+ * @shm:		Memory pool shared with RTC device.
+ * @features:		Bitfield of RTC features
+ * @alarm_task:		RTC wait alamr task.
+ * @rtc:		RTC device.
+ */
+struct optee_rtc {
+	struct device *dev;
+	struct tee_context *ctx;
+	u32 session_id;
+	u32 session2_id;
+	struct tee_shm *shm;
+	u64 features;
+	struct task_struct *alarm_task;
+	struct rtc_device *rtc;
+};
+
+static int optee_rtc_readtime(struct device *dev, struct rtc_time *tm)
+{
+	struct optee_rtc *priv = dev_get_drvdata(dev);
+	struct tee_ioctl_invoke_arg inv_arg = {0};
+	struct optee_rtc_time *optee_tm;
+	struct tee_param param[4] = {0};
+	int ret;
+
+	inv_arg.func = PTA_CMD_RTC_GET_TIME;
+	inv_arg.session = priv->session_id;
+	inv_arg.num_params = 4;
+
+	/* Fill invoke cmd params */
+	param[0].attr = TEE_IOCTL_PARAM_ATTR_TYPE_MEMREF_OUTPUT;
+	param[0].u.memref.shm = priv->shm;
+	param[0].u.memref.size = sizeof(struct optee_rtc_time);
+
+	ret = tee_client_invoke_func(priv->ctx, &inv_arg, param);
+	if (ret < 0 || inv_arg.ret != 0)
+		return ret ? ret : -EPROTO;
+
+	optee_tm = tee_shm_get_va(priv->shm, 0);
+	if (IS_ERR(optee_tm))
+		return PTR_ERR(optee_tm);
+
+	if (param[0].u.memref.size != sizeof(*optee_tm))
+		return -EPROTO;
+
+	tm->tm_sec = optee_tm->tm_sec;
+	tm->tm_min = optee_tm->tm_min;
+	tm->tm_hour = optee_tm->tm_hour;
+	tm->tm_mday = optee_tm->tm_mday;
+	tm->tm_mon = optee_tm->tm_mon;
+	tm->tm_year = optee_tm->tm_year - 1900;
+	tm->tm_wday = optee_tm->tm_wday;
+	tm->tm_yday = rtc_year_days(tm->tm_mday, tm->tm_mon, tm->tm_year);
+
+	return 0;
+}
+
+static int optee_rtc_settime(struct device *dev, struct rtc_time *tm)
+{
+	struct optee_rtc *priv = dev_get_drvdata(dev);
+	struct tee_ioctl_invoke_arg inv_arg = {0};
+	struct tee_param param[4] = {0};
+	struct optee_rtc_time *optee_tm;
+	int ret;
+
+	inv_arg.func = PTA_CMD_RTC_SET_TIME;
+	inv_arg.session = priv->session_id;
+	inv_arg.num_params = 4;
+
+	param[0].attr = TEE_IOCTL_PARAM_ATTR_TYPE_MEMREF_INPUT;
+	param[0].u.memref.shm = priv->shm;
+	param[0].u.memref.size = sizeof(struct optee_rtc_time);
+
+	optee_tm = tee_shm_get_va(priv->shm, 0);
+	if (IS_ERR(optee_tm))
+		return PTR_ERR(optee_tm);
+
+	optee_tm->tm_min = tm->tm_min;
+	optee_tm->tm_sec = tm->tm_sec;
+	optee_tm->tm_hour = tm->tm_hour;
+	optee_tm->tm_mday = tm->tm_mday;
+	optee_tm->tm_mon = tm->tm_mon;
+	optee_tm->tm_year = tm->tm_year + 1900;
+	optee_tm->tm_wday = tm->tm_wday;
+
+	ret = tee_client_invoke_func(priv->ctx, &inv_arg, param);
+	if (ret < 0 || inv_arg.ret != 0)
+		return ret ? ret : -EPROTO;
+
+	return 0;
+}
+
+static int optee_rtc_readoffset(struct device *dev, long *offset)
+{
+	struct optee_rtc *priv = dev_get_drvdata(dev);
+	struct tee_ioctl_invoke_arg inv_arg = {0};
+	struct tee_param param[4] = {0};
+	int ret;
+
+	if (!(priv->features & TA_RTC_FEATURE_CORRECTION))
+		return -EOPNOTSUPP;
+
+	inv_arg.func = PTA_CMD_RTC_GET_OFFSET;
+	inv_arg.session = priv->session_id;
+	inv_arg.num_params = 4;
+
+	param[0].attr = TEE_IOCTL_PARAM_ATTR_TYPE_VALUE_OUTPUT;
+
+	ret = tee_client_invoke_func(priv->ctx, &inv_arg, param);
+	if (ret < 0 || inv_arg.ret != 0)
+		return ret ? ret : -EPROTO;
+
+	*offset = param[0].u.value.a;
+
+	return 0;
+}
+
+static int optee_rtc_setoffset(struct device *dev, long offset)
+{
+	struct optee_rtc *priv = dev_get_drvdata(dev);
+	struct tee_ioctl_invoke_arg inv_arg = {0};
+	struct tee_param param[4] = {0};
+	int ret;
+
+	if (!(priv->features & TA_RTC_FEATURE_CORRECTION))
+		return -EOPNOTSUPP;
+
+	inv_arg.func = PTA_CMD_RTC_SET_OFFSET;
+	inv_arg.session = priv->session_id;
+	inv_arg.num_params = 4;
+
+	param[0].attr = TEE_IOCTL_PARAM_ATTR_TYPE_VALUE_INPUT;
+	param[0].u.value.a = offset;
+
+	ret = tee_client_invoke_func(priv->ctx, &inv_arg, param);
+	if (ret < 0 || inv_arg.ret != 0)
+		return ret ? ret : -EPROTO;
+
+	return 0;
+}
+
+static int optee_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alarm)
+{
+	struct optee_rtc *priv = dev_get_drvdata(dev);
+	struct tee_ioctl_invoke_arg inv_arg = {0};
+	struct optee_rtc_alarm *optee_alarm;
+	struct tee_param param[1] = {0};
+	int ret;
+
+	if (!(priv->features & TA_RTC_FEATURE_ALARM))
+		return -EOPNOTSUPP;
+
+	inv_arg.func = PTA_CMD_RTC_READ_ALARM;
+	inv_arg.session = priv->session_id;
+	inv_arg.num_params = 1;
+
+	/* Fill invoke cmd params */
+	param[0].attr = TEE_IOCTL_PARAM_ATTR_TYPE_MEMREF_OUTPUT;
+	param[0].u.memref.shm = priv->shm;
+	param[0].u.memref.size = sizeof(struct optee_rtc_alarm);
+
+	ret = tee_client_invoke_func(priv->ctx, &inv_arg, param);
+	if (ret < 0 || inv_arg.ret != 0)
+		return ret ? ret : -EPROTO;
+
+	optee_alarm = tee_shm_get_va(priv->shm, 0);
+	if (IS_ERR(optee_alarm))
+		return PTR_ERR(optee_alarm);
+
+	if (param[0].u.memref.size != sizeof(*optee_alarm))
+		return -EPROTO;
+
+	alarm->enabled = optee_alarm->enabled;
+	alarm->pending = optee_alarm->pending;
+	alarm->time.tm_sec = optee_alarm->time.tm_sec;
+	alarm->time.tm_min = optee_alarm->time.tm_min;
+	alarm->time.tm_hour = optee_alarm->time.tm_hour;
+	alarm->time.tm_mday = optee_alarm->time.tm_mday;
+	alarm->time.tm_mon = optee_alarm->time.tm_mon;
+	alarm->time.tm_year = optee_alarm->time.tm_year - 1900;
+	alarm->time.tm_wday = optee_alarm->time.tm_wday;
+	alarm->time.tm_yday = rtc_year_days(alarm->time.tm_mday,
+					    alarm->time.tm_mon,
+					    alarm->time.tm_year);
+
+	return 0;
+}
+
+static int optee_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alarm)
+{
+	struct optee_rtc *priv = dev_get_drvdata(dev);
+	struct tee_ioctl_invoke_arg inv_arg = {0};
+	struct optee_rtc_alarm *optee_alarm;
+	struct tee_param param[1] = {0};
+	int ret;
+
+	if (!(priv->features & TA_RTC_FEATURE_ALARM))
+		return -EOPNOTSUPP;
+
+	inv_arg.func = PTA_CMD_RTC_SET_ALARM;
+	inv_arg.session = priv->session_id;
+	inv_arg.num_params = 1;
+
+	param[0].attr = TEE_IOCTL_PARAM_ATTR_TYPE_MEMREF_INPUT;
+	param[0].u.memref.shm = priv->shm;
+	param[0].u.memref.size = sizeof(struct optee_rtc_alarm);
+
+	optee_alarm = tee_shm_get_va(priv->shm, 0);
+	if (IS_ERR(optee_alarm))
+		return PTR_ERR(optee_alarm);
+
+	optee_alarm->enabled = alarm->enabled;
+	optee_alarm->pending = alarm->pending;
+	optee_alarm->time.tm_sec = alarm->time.tm_sec;
+	optee_alarm->time.tm_min = alarm->time.tm_min;
+	optee_alarm->time.tm_hour = alarm->time.tm_hour;
+	optee_alarm->time.tm_mday = alarm->time.tm_mday;
+	optee_alarm->time.tm_mon = alarm->time.tm_mon;
+	optee_alarm->time.tm_year = alarm->time.tm_year + 1900;
+	optee_alarm->time.tm_wday = alarm->time.tm_wday;
+
+	ret = tee_client_invoke_func(priv->ctx, &inv_arg, param);
+	if (ret < 0 || inv_arg.ret != 0)
+		return ret ? ret : -EPROTO;
+
+	return 0;
+}
+
+static int optee_rtc_enable_alarm(struct device *dev, unsigned int enabled)
+{
+	struct optee_rtc *priv = dev_get_drvdata(dev);
+	struct tee_ioctl_invoke_arg inv_arg = {0};
+	struct tee_param param[1] = {0};
+	int ret;
+
+	if (!(priv->features & TA_RTC_FEATURE_ALARM))
+		return -EOPNOTSUPP;
+
+	inv_arg.func = PTA_CMD_RTC_ENABLE_ALARM;
+	inv_arg.session = priv->session_id;
+	inv_arg.num_params = 1;
+
+	param[0].attr = TEE_IOCTL_PARAM_ATTR_TYPE_VALUE_INPUT;
+	param[0].u.value.a = (bool)enabled;
+
+	ret = tee_client_invoke_func(priv->ctx, &inv_arg, param);
+	if (ret < 0 || inv_arg.ret != 0)
+		return ret ? ret : -EPROTO;
+
+	return 0;
+}
+
+static const struct rtc_class_ops optee_rtc_ops = {
+	.read_time		= optee_rtc_readtime,
+	.set_time		= optee_rtc_settime,
+	.set_offset		= optee_rtc_setoffset,
+	.read_offset		= optee_rtc_readoffset,
+	.read_alarm		= optee_rtc_read_alarm,
+	.set_alarm		= optee_rtc_set_alarm,
+	.alarm_irq_enable	= optee_rtc_enable_alarm,
+};
+
+static int optee_rtc_wait_alarm(struct device *dev, int *return_status)
+{
+	struct optee_rtc *priv = dev_get_drvdata(dev);
+	struct tee_ioctl_invoke_arg inv_arg = {0};
+	struct tee_param param[1] = {0};
+	int ret;
+
+	if (!(priv->features & TA_RTC_FEATURE_ALARM))
+		return -EOPNOTSUPP;
+
+	inv_arg.func = PTA_CMD_RTC_WAIT_ALARM;
+	inv_arg.session = priv->session2_id;
+	inv_arg.num_params = 1;
+
+	param[0].attr = TEE_IOCTL_PARAM_ATTR_TYPE_VALUE_OUTPUT;
+
+	ret = tee_client_invoke_func(priv->ctx, &inv_arg, param);
+	if (ret < 0 || inv_arg.ret != 0)
+		return ret ? ret : -EPROTO;
+
+	*return_status = param[0].u.value.a;
+
+	return 0;
+}
+
+static int optee_rtc_cancel_wait_alarm(struct device *dev)
+{
+	struct optee_rtc *priv = dev_get_drvdata(dev);
+	struct tee_ioctl_invoke_arg inv_arg = {0};
+	struct tee_param param[1] = {0};
+	int ret;
+
+	if (!(priv->features & TA_RTC_FEATURE_ALARM))
+		return -EOPNOTSUPP;
+
+	inv_arg.func = PTA_CMD_RTC_CANCEL_WAIT;
+	inv_arg.session = priv->session_id;
+	inv_arg.num_params = 0;
+
+	ret = tee_client_invoke_func(priv->ctx, &inv_arg, param);
+	if (ret < 0 || inv_arg.ret != 0)
+		return ret ? ret : -EPROTO;
+
+	return 0;
+}
+
+static int optee_rtc_set_alarm_wake_status(struct device *dev, bool status)
+{
+	struct optee_rtc *priv = dev_get_drvdata(dev);
+	struct tee_ioctl_invoke_arg inv_arg = {0};
+	struct tee_param param[1] = {0};
+	int ret;
+
+	if (!(priv->features & TA_RTC_FEATURE_ALARM))
+		return -EOPNOTSUPP;
+
+	inv_arg.func = PTA_CMD_RTC_SET_WAKE_ALARM_STATUS;
+	inv_arg.session = priv->session_id;
+	inv_arg.num_params = 1;
+
+	param[0].attr = TEE_IOCTL_PARAM_ATTR_TYPE_VALUE_INPUT;
+	param[0].u.value.a = status;
+
+	ret = tee_client_invoke_func(priv->ctx, &inv_arg, param);
+
+	if (ret < 0 || inv_arg.ret != 0)
+		return ret ? ret : -EPROTO;
+
+	return 0;
+}
+
+static int optee_rtc_handle_alarm_event(void *data)
+{
+	struct optee_rtc *priv = (struct optee_rtc *)data;
+	int wait_alarm_return_status = 0;
+	int ret;
+
+	while (!kthread_should_stop()) {
+		ret = optee_rtc_wait_alarm(priv->dev, &wait_alarm_return_status);
+		if (ret) {
+			dev_err(priv->dev, "Failed to wait for alarm: %d\n", ret);
+			return ret;
+		}
+		switch (wait_alarm_return_status) {
+		case WAIT_ALARM_ALARM_OCCURRED:
+			dev_dbg(priv->dev, "Alarm occurred\n");
+			rtc_update_irq(priv->rtc, 1, RTC_IRQF | RTC_AF);
+			break;
+		case WAIT_ALARM_CANCELED:
+			dev_dbg(priv->dev, "Alarm canceled\n");
+			break;
+		default:
+			dev_warn(priv->dev, "Unknown return status: %d\n",
+				 wait_alarm_return_status);
+			break;
+		}
+	}
+
+	return 0;
+}
+
+static int optee_rtc_read_info(struct device *dev, struct rtc_device *rtc,
+			       u64 *features)
+{
+	struct optee_rtc *priv = dev_get_drvdata(dev);
+	struct tee_ioctl_invoke_arg inv_arg = {0};
+	struct tee_param param[4] = {0};
+	struct optee_rtc_info *info;
+	struct optee_rtc_time *tm;
+	int ret;
+
+	inv_arg.func = PTA_CMD_RTC_GET_INF;
+	inv_arg.session = priv->session_id;
+	inv_arg.num_params = 4;
+
+	param[0].attr = TEE_IOCTL_PARAM_ATTR_TYPE_MEMREF_OUTPUT;
+	param[0].u.memref.shm = priv->shm;
+	param[0].u.memref.size = sizeof(*info);
+
+	ret = tee_client_invoke_func(priv->ctx, &inv_arg, param);
+	if (ret < 0 || inv_arg.ret != 0)
+		return ret ? ret : -EPROTO;
+
+	info = tee_shm_get_va(priv->shm, 0);
+	if (IS_ERR(info))
+		return PTR_ERR(info);
+
+	if (param[0].u.memref.size != sizeof(*info))
+		return -EPROTO;
+
+	if (info->version != RTC_INFO_VERSION)
+		return -EPROTO;
+
+	*features = info->features;
+
+	tm = &info->range_min;
+	rtc->range_min = mktime64(tm->tm_year, tm->tm_mon, tm->tm_mday, tm->tm_hour, tm->tm_min,
+				  tm->tm_sec);
+	tm = &info->range_max;
+	rtc->range_max = mktime64(tm->tm_year, tm->tm_mon, tm->tm_mday, tm->tm_hour, tm->tm_min,
+				  tm->tm_sec);
+
+	return 0;
+}
+
+static int optee_ctx_match(struct tee_ioctl_version_data *ver, const void *data)
+{
+	return (ver->impl_id == TEE_IMPL_ID_OPTEE);
+}
+
+static int optee_rtc_probe(struct tee_client_device *rtc_device)
+{
+	struct device *dev = &rtc_device->dev;
+	struct tee_ioctl_open_session_arg sess2_arg = {0};
+	struct tee_ioctl_open_session_arg sess_arg = {0};
+	struct optee_rtc *priv;
+	struct rtc_device *rtc;
+	struct tee_shm *shm;
+	int ret, err;
+
+	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	rtc = devm_rtc_allocate_device(dev);
+	if (IS_ERR(rtc))
+		return PTR_ERR(rtc);
+
+	priv->rtc = rtc;
+
+	/* Open context with TEE driver */
+	priv->ctx = tee_client_open_context(NULL, optee_ctx_match, NULL, NULL);
+	if (IS_ERR(priv->ctx))
+		return -ENODEV;
+
+	/* Open first session with rtc Pseudo Trusted App */
+	export_uuid(sess_arg.uuid, &rtc_device->id.uuid);
+	sess_arg.clnt_login = TEE_IOCTL_LOGIN_REE_KERNEL;
+
+	ret = tee_client_open_session(priv->ctx, &sess_arg, NULL);
+	if (ret < 0 || sess_arg.ret != 0) {
+		dev_err(dev, "tee_client_open_session failed, err: %x\n", sess_arg.ret);
+		err = -EINVAL;
+		goto out_ctx;
+	}
+	priv->session_id = sess_arg.session;
+
+	/*
+	 * Shared memory is used for passing an instance of either struct optee_rtc_info,
+	 * struct optee_rtc_time or struct optee_rtc_alarm to OP-TEE service.
+	 * The former is by definition large enough to cover both parameter cases.
+	 */
+	shm = tee_shm_alloc_kernel_buf(priv->ctx, sizeof(struct optee_rtc_info));
+	if (IS_ERR(shm)) {
+		dev_err(priv->dev, "tee_shm_alloc_kernel_buf failed\n");
+		err = PTR_ERR(shm);
+		goto out_sess;
+	}
+
+	priv->shm = shm;
+	priv->dev = dev;
+	dev_set_drvdata(dev, priv);
+
+	rtc->ops = &optee_rtc_ops;
+
+	err = optee_rtc_read_info(dev, rtc, &priv->features);
+	if (err) {
+		dev_err(dev, "Failed to get RTC features from OP-TEE\n");
+		goto out_shm;
+	}
+
+	/* Handle feature's related setup before registering to rtc framework */
+	if (priv->features & TA_RTC_FEATURE_ALARM) {
+		priv->alarm_task = kthread_create(optee_rtc_handle_alarm_event,
+						  priv, "rtc_alarm_evt");
+		if (IS_ERR(priv->alarm_task)) {
+			dev_err(dev, "Failed to create alarm thread\n");
+			err = PTR_ERR(priv->alarm_task);
+			goto out_shm;
+		}
+
+		/*
+		 * In case of supported alarm feature on optee side, we create a kthread
+		 * that will, in a new optee session, call a PTA interface "rtc_wait_alarm".
+		 * This call return in case of alarm and in case of canceled alarm.
+		 * The new optee session is therefore only needed in this case as we cannot
+		 * use the same session for parallel calls to optee PTA.
+		 * Hence one session is reserved to wait for alarms and the other to make
+		 * standard calls to RTC PTA.
+		 */
+
+		/* Open second session with rtc Trusted App */
+		export_uuid(sess2_arg.uuid, &rtc_device->id.uuid);
+		sess2_arg.clnt_login = TEE_IOCTL_LOGIN_REE_KERNEL;
+
+		ret = tee_client_open_session(priv->ctx, &sess2_arg, NULL);
+		if (ret < 0 || sess2_arg.ret != 0) {
+			dev_err(dev, "tee_client_open_session failed, err: %x\n", sess2_arg.ret);
+			err = -EINVAL;
+			goto out_thrd;
+		}
+		priv->session2_id = sess2_arg.session;
+
+		if (priv->features & TA_RTC_FEATURE_WAKEUP_ALARM)
+			device_init_wakeup(dev, true);
+	}
+
+	err = devm_rtc_register_device(rtc);
+	if (err)
+		goto out_wk;
+
+	/*
+	 * We must clear those bits after registering because registering a rtc_device
+	 * will set them if it sees that .set_offset and .set_alarm are provided.
+	 */
+	if (!(priv->features & TA_RTC_FEATURE_CORRECTION))
+		clear_bit(RTC_FEATURE_CORRECTION, rtc->features);
+	if (!(priv->features & TA_RTC_FEATURE_ALARM))
+		clear_bit(RTC_FEATURE_ALARM, rtc->features);
+
+	/* Start the thread after the rtc is setup */
+	if (priv->alarm_task) {
+		wake_up_process(priv->alarm_task);
+		dev_dbg(dev, "Wait alarm thread successfully started\n");
+	}
+
+	return 0;
+out_wk:
+	if (priv->features & TA_RTC_FEATURE_ALARM) {
+		device_init_wakeup(dev, false);
+		tee_client_close_session(priv->ctx, priv->session2_id);
+	}
+out_thrd:
+	if (priv->features & TA_RTC_FEATURE_ALARM)
+		kthread_stop(priv->alarm_task);
+out_shm:
+	tee_shm_free(priv->shm);
+out_sess:
+	tee_client_close_session(priv->ctx, priv->session_id);
+out_ctx:
+	tee_client_close_context(priv->ctx);
+
+	return err;
+}
+
+static void optee_rtc_remove(struct tee_client_device *rtc_device)
+{
+	struct device *dev = &rtc_device->dev;
+	struct optee_rtc *priv = dev_get_drvdata(dev);
+
+	if (priv->features & TA_RTC_FEATURE_ALARM) {
+		optee_rtc_cancel_wait_alarm(dev);
+		kthread_stop(priv->alarm_task);
+		device_init_wakeup(dev, false);
+		tee_client_close_session(priv->ctx, priv->session2_id);
+	}
+
+	tee_shm_free(priv->shm);
+	tee_client_close_session(priv->ctx, priv->session_id);
+	tee_client_close_context(priv->ctx);
+}
+
+static int optee_rtc_suspend(struct device *dev)
+{
+	int res = optee_rtc_set_alarm_wake_status(dev, device_may_wakeup(dev));
+
+	if (res) {
+		dev_err(dev, "Unable to transmit wakeup information to optee rtc\n");
+		return res;
+	}
+
+	return 0;
+}
+
+static DEFINE_SIMPLE_DEV_PM_OPS(optee_rtc_pm_ops, optee_rtc_suspend, NULL);
+
+static const struct tee_client_device_id optee_rtc_id_table[] = {
+	{UUID_INIT(0xf389f8c8, 0x845f, 0x496c,
+		   0x8b, 0xbe, 0xd6, 0x4b, 0xd2, 0x4c, 0x92, 0xfd)},
+	{}
+};
+
+MODULE_DEVICE_TABLE(tee, optee_rtc_id_table);
+
+static struct tee_client_driver optee_rtc_driver = {
+	.id_table	= optee_rtc_id_table,
+	.probe		= optee_rtc_probe,
+	.remove		= optee_rtc_remove,
+	.driver		= {
+		.name		= "optee_rtc",
+		.pm		= pm_sleep_ptr(&optee_rtc_pm_ops),
+	},
+};
+
+module_tee_client_driver(optee_rtc_driver);
+
+MODULE_LICENSE("GPL v2");
+MODULE_AUTHOR("Clément Léger <clement.leger@bootlin.com>");
+MODULE_DESCRIPTION("OP-TEE based RTC driver");