[PATCH v14 0/4] Add support for Intel PPS Generator

[PATCH v14 0/4] Add support for Intel PPS Generator

[subramanian.mohan]

From: Subramanian Mohan <subramanian.mohan@intel.com>

The goal of the PPS (Pulse Per Second) hardware/software is to generate a
signal from the system on a wire so that some third-party hardware can
observe that signal and judge how close the system's time is to another
system or piece of hardware.

Existing methods (like parallel ports) require software to flip a bit at
just the right time to create a PPS signal. Many things can prevent
software from doing this precisely. This (Timed I/O) method is better
because software only "arms" the hardware in advance and then depends on
the hardware to "fire" and flip the signal at just the right time.

To generate a PPS signal with this new hardware, the kernel wakes up
twice a second, once for 1->0 edge and other for the 0->1 edge. It does
this shortly (~10ms) before the actual change in the signal needs to be
made. It computes the TSC value at which edge will happen, convert to a
value hardware understands and program this value to Timed I/O hardware.
The actual edge transition happens without any further action from the
kernel.

The result here is a signal coming out of the system that is roughly
1,000 times more accurate than the old methods. If the system is heavily
loaded, the difference in accuracy is larger in old methods.

Application Interface:
The API to use Timed I/O is very simple. It is enabled and disabled by
writing a '1' or '0' value to the sysfs enable attribute associated with
the Timed I/O PPS device. Each Timed I/O pin is represented by a PPS
device. When enabled, a pulse-per-second (PPS) synchronized with the
system clock is continuously produced on the Timed I/O pin, otherwise it
is pulled low.

The Timed I/O signal on the motherboard is enabled in the BIOS setup.
Intel Advanced Menu -> PCH IO Configuration -> Timed I/O <Enable>

References:
https://en.wikipedia.org/wiki/Pulse-per-second_signal
https://drive.google.com/file/d/1vkBRRDuELmY8I3FlfOZaEBp-DxLW6t_V/view
https://youtu.be/JLUTT-lrDqw

Patch 1 Replaced copy of pps-gen info struct with const pointer in
pps-gen framework..
Patch 2 adds the pps(pulse per second) generator tio driver to the pps
subsystem.
Patch 3 documentation and usage of the pps tio generator module.
Patch 4 includes documentation for sysfs interface.

These patches are based on the timers/core branch:
[1] https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git/?h=timers/core
These changes are dependent on patches that are merged in [1].

Please help to review the changes.

Thanks in advance,
Subramanian Mohan

Changes from v2:
 - Split patch 1 to remove the functions in later stages.
 - Include required headers in pps_gen_tio.

Changes from v3:
 - Corrections in Documentation.
 - Introducing non-RFC version of the patch series.

Changes from v4:
 - Setting id in ice_ptp
 - Modified conversion logic in convert_base_to_cs.
 - Included the usage of the APIs in the commit message of 2nd patch.

Changes from v5:
 - Change nsecs variable to use_nsecs.
 - Change order of 1&2 patches and modify the commit message.
 - Add sysfs abi file entry in MAINTAINERS file.
 - Add check to find if any event is missed and disable hardware
   accordingly.

Changes from v6:
 - Split patch 1 into 1&2 patches.
 - Add check for overflow in convert_ns_to_cs().
 - Refine commit messages.

Changes from v7:
 - Split the if condition and return error if current time exceeds
   expire time.
 - Update kernel version and month in ABI file.

Changes from v8:
 - Add function to enable Timed I/O.
 - Changed the updating of tio->enabled to a centralized place in
   disable and enable functions.

Changes from v9:
 - use tio->enabled instead of reading ctrl register.
 - change error code in enable_store to -ENODEV.

Changes from v10:
 - Rebased to latest codebase.

Changes from v11:
 - Rebased to latest codebase.

Changes from v12:
 - As part of pps-gen framework, Replaced copy of pps-gen info struct
   with const pointer.
 - TIO driver adapted to pps-gen framework.
 - Fixed review comments by Andy.
 - Rebased to latest codebase.

Changes from v13:
 - Fixed review comments by Andy.
 - Rebased to latest codebase.

Subramanian Mohan (4):
  drivers pps/generators: replace copy of pps-gen info struct with const
    pointer
  pps: generators: Add PPS Generator TIO Driver
  Documentation: driver-api: pps: Add Intel Timed I/O PPS generator
  ABI: pps: Add ABI documentation for Intel TIO

 Documentation/ABI/testing/sysfs-pps-gen-tio |   6 +
 Documentation/driver-api/pps.rst            |  27 +-
 MAINTAINERS                                 |   1 +
 drivers/pps/generators/Kconfig              |  16 ++
 drivers/pps/generators/Makefile             |   1 +
 drivers/pps/generators/pps_gen-dummy.c      |   2 +-
 drivers/pps/generators/pps_gen.c            |  14 +-
 drivers/pps/generators/pps_gen_tio.c        | 272 ++++++++++++++++++++
 drivers/pps/generators/sysfs.c              |   6 +-
 include/linux/pps_gen_kernel.h              |   4 +-
 10 files changed, 334 insertions(+), 15 deletions(-)
 create mode 100644 Documentation/ABI/testing/sysfs-pps-gen-tio
 create mode 100644 drivers/pps/generators/pps_gen_tio.c

-- 
2.35.3

[PATCH v14 1/4] drivers pps/generators: replace copy of pps-gen info struct with const pointer

[subramanian.mohan]

From: Subramanian Mohan <subramanian.mohan@intel.com>

Some PPS generator drivers may need to retrieve a pointer to their
internal data while executing the PPS generator enable() method.

During the driver registration the pps_gen_device pointer is returned
from the framework, and for that reason, there is difficulty in
getting generator driver data back in the enable function. We won't be
able to use container_of macro as it results in static assert, and we
might end up in using static pointer.

To solve the issue and to get back the generator driver data back, we
should not copy the struct pps_gen_source_info within the struct
pps_gen_device during the registration stage, but simply save the
pointer of the driver one. In this manner, driver may get a pointer
to their internal data as shown below:

struct pps_gen_foo_data_s {
        ...
	struct pps_gen_source_info gen_info;
	struct pps_gen_device *pps_gen;
	...
};

static int __init pps_gen_foo_init(void)
{
        struct pps_gen_foo_data_s *foo;
	...
        foo->pps_gen = pps_gen_register_source(&foo->gen_info);
	...
}

Then, in the enable() method, we can retrieve the pointer to the main
struct by using the code below:

static int pps_gen_foo_enable(struct pps_gen_device *pps_gen, bool enable)
{
        struct pps_gen_foo_data_s *foo = container_of(pps_gen->info,
						struct pps_gen_foo_data_s, gen_info);
        ...
}

Signed-off-by: Rodolfo Giometti <giometti@enneenne.com>
Tested-by: Subramanian Mohan <subramanian.mohan@intel.com>
Suggested-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Subramanian Mohan <subramanian.mohan@intel.com>
---
 Documentation/driver-api/pps.rst       |  3 +--
 drivers/pps/generators/pps_gen-dummy.c |  2 +-
 drivers/pps/generators/pps_gen.c       | 14 +++++++-------
 drivers/pps/generators/sysfs.c         |  6 +++---
 include/linux/pps_gen_kernel.h         |  4 ++--
 5 files changed, 14 insertions(+), 15 deletions(-)

diff --git a/Documentation/driver-api/pps.rst b/Documentation/driver-api/pps.rst
index 71ad04c82d6c..04f1b88778fc 100644
--- a/Documentation/driver-api/pps.rst
+++ b/Documentation/driver-api/pps.rst
@@ -206,8 +206,7 @@ To do so the class pps-gen has been added. PPS generators can be
 registered in the kernel by defining a struct pps_gen_source_info as
 follows::
 
-    static struct pps_gen_source_info pps_gen_dummy_info = {
-            .name                   = "dummy",
+    static const struct pps_gen_source_info pps_gen_dummy_info = {
             .use_system_clock       = true,
             .get_time               = pps_gen_dummy_get_time,
             .enable                 = pps_gen_dummy_enable,
diff --git a/drivers/pps/generators/pps_gen-dummy.c b/drivers/pps/generators/pps_gen-dummy.c
index b284c200cbe5..55de4aecf35e 100644
--- a/drivers/pps/generators/pps_gen-dummy.c
+++ b/drivers/pps/generators/pps_gen-dummy.c
@@ -61,7 +61,7 @@ static int pps_gen_dummy_enable(struct pps_gen_device *pps_gen, bool enable)
  * The PPS info struct
  */
 
-static struct pps_gen_source_info pps_gen_dummy_info = {
+static const struct pps_gen_source_info pps_gen_dummy_info = {
 	.use_system_clock	= true,
 	.get_time		= pps_gen_dummy_get_time,
 	.enable			= pps_gen_dummy_enable,
diff --git a/drivers/pps/generators/pps_gen.c b/drivers/pps/generators/pps_gen.c
index ca592f1736f4..5b8bb454913c 100644
--- a/drivers/pps/generators/pps_gen.c
+++ b/drivers/pps/generators/pps_gen.c
@@ -66,7 +66,7 @@ static long pps_gen_cdev_ioctl(struct file *file,
 		if (ret)
 			return -EFAULT;
 
-		ret = pps_gen->info.enable(pps_gen, status);
+		ret = pps_gen->info->enable(pps_gen, status);
 		if (ret)
 			return ret;
 		pps_gen->enabled = status;
@@ -76,7 +76,7 @@ static long pps_gen_cdev_ioctl(struct file *file,
 	case PPS_GEN_USESYSTEMCLOCK:
 		dev_dbg(pps_gen->dev, "PPS_GEN_USESYSTEMCLOCK\n");
 
-		ret = put_user(pps_gen->info.use_system_clock, uiuarg);
+		ret = put_user(pps_gen->info->use_system_clock, uiuarg);
 		if (ret)
 			return -EFAULT;
 
@@ -175,7 +175,7 @@ static int pps_gen_register_cdev(struct pps_gen_device *pps_gen)
 	devt = MKDEV(MAJOR(pps_gen_devt), pps_gen->id);
 
 	cdev_init(&pps_gen->cdev, &pps_gen_cdev_fops);
-	pps_gen->cdev.owner = pps_gen->info.owner;
+	pps_gen->cdev.owner = pps_gen->info->owner;
 
 	err = cdev_add(&pps_gen->cdev, devt, 1);
 	if (err) {
@@ -183,8 +183,8 @@ static int pps_gen_register_cdev(struct pps_gen_device *pps_gen)
 				MAJOR(pps_gen_devt), pps_gen->id);
 		goto free_ida;
 	}
-	pps_gen->dev = device_create(pps_gen_class, pps_gen->info.parent, devt,
-					pps_gen, "pps-gen%d", pps_gen->id);
+	pps_gen->dev = device_create(pps_gen_class, pps_gen->info->parent, devt,
+				     pps_gen, "pps-gen%d", pps_gen->id);
 	if (IS_ERR(pps_gen->dev)) {
 		err = PTR_ERR(pps_gen->dev);
 		goto del_cdev;
@@ -225,7 +225,7 @@ static void pps_gen_unregister_cdev(struct pps_gen_device *pps_gen)
  * Return: the PPS generator device in case of success, and ERR_PTR(errno)
  *	 otherwise.
  */
-struct pps_gen_device *pps_gen_register_source(struct pps_gen_source_info *info)
+struct pps_gen_device *pps_gen_register_source(const struct pps_gen_source_info *info)
 {
 	struct pps_gen_device *pps_gen;
 	int err;
@@ -235,7 +235,7 @@ struct pps_gen_device *pps_gen_register_source(struct pps_gen_source_info *info)
 		err = -ENOMEM;
 		goto pps_gen_register_source_exit;
 	}
-	pps_gen->info = *info;
+	pps_gen->info = info;
 	pps_gen->enabled = false;
 
 	init_waitqueue_head(&pps_gen->queue);
diff --git a/drivers/pps/generators/sysfs.c b/drivers/pps/generators/sysfs.c
index faf8b1c6d202..6d6bc0006fea 100644
--- a/drivers/pps/generators/sysfs.c
+++ b/drivers/pps/generators/sysfs.c
@@ -19,7 +19,7 @@ static ssize_t system_show(struct device *dev, struct device_attribute *attr,
 {
 	struct pps_gen_device *pps_gen = dev_get_drvdata(dev);
 
-	return sysfs_emit(buf, "%d\n", pps_gen->info.use_system_clock);
+	return sysfs_emit(buf, "%d\n", pps_gen->info->use_system_clock);
 }
 static DEVICE_ATTR_RO(system);
 
@@ -30,7 +30,7 @@ static ssize_t time_show(struct device *dev, struct device_attribute *attr,
 	struct timespec64 time;
 	int ret;
 
-	ret = pps_gen->info.get_time(pps_gen, &time);
+	ret = pps_gen->info->get_time(pps_gen, &time);
 	if (ret)
 		return ret;
 
@@ -49,7 +49,7 @@ static ssize_t enable_store(struct device *dev, struct device_attribute *attr,
 	if (ret)
 		return ret;
 
-	ret = pps_gen->info.enable(pps_gen, status);
+	ret = pps_gen->info->enable(pps_gen, status);
 	if (ret)
 		return ret;
 	pps_gen->enabled = status;
diff --git a/include/linux/pps_gen_kernel.h b/include/linux/pps_gen_kernel.h
index 022ea0ac4440..6214c8aa2e02 100644
--- a/include/linux/pps_gen_kernel.h
+++ b/include/linux/pps_gen_kernel.h
@@ -43,7 +43,7 @@ struct pps_gen_source_info {
 
 /* The main struct */
 struct pps_gen_device {
-	struct pps_gen_source_info info;	/* PSS generator info */
+	const struct pps_gen_source_info *info;	/* PSS generator info */
 	bool enabled;				/* PSS generator status */
 
 	unsigned int event;
@@ -70,7 +70,7 @@ extern const struct attribute_group *pps_gen_groups[];
  */
 
 extern struct pps_gen_device *pps_gen_register_source(
-				struct pps_gen_source_info *info);
+				const struct pps_gen_source_info *info);
 extern void pps_gen_unregister_source(struct pps_gen_device *pps_gen);
 extern void pps_gen_event(struct pps_gen_device *pps_gen,
 				unsigned int event, void *data);
-- 
2.35.3

[PATCH v14 2/4] pps: generators: Add PPS Generator TIO Driver

[subramanian.mohan]

From: Subramanian Mohan <subramanian.mohan@intel.com>

The Intel Timed IO PPS generator driver outputs a PPS signal using
dedicated hardware that is more accurate than software actuated PPS.
The Timed IO hardware generates output events using the ART timer.
The ART timer period varies based on platform type, but is less than 100
nanoseconds for all current platforms. Timed IO output accuracy is
within 1 ART period.

PPS output is enabled by writing '1' the 'enable' sysfs attribute. The
driver uses hrtimers to schedule a wake-up 10 ms before each event
(edge) target time. At wakeup, the driver converts the target time in
terms of CLOCK_REALTIME to ART trigger time and writes this to the Timed
IO hardware. The Timed IO hardware generates an event precisely at the
requested system time without software involvement.

Co-developed-by: Christopher Hall <christopher.s.hall@intel.com>
Signed-off-by: Christopher Hall <christopher.s.hall@intel.com>
Co-developed-by: Pandith N <pandith.n@intel.com>
Signed-off-by: Pandith N <pandith.n@intel.com>
Co-developed-by: Thejesh Reddy T R <thejesh.reddy.t.r@intel.com>
Signed-off-by: Thejesh Reddy T R <thejesh.reddy.t.r@intel.com>
Signed-off-by: Lakshmi Sowjanya D <lakshmi.sowjanya.d@intel.com>
Reviewed-by: Eddie Dong <eddie.dong@intel.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Rodolfo Giometti <giometti@enneenne.com>
Signed-off-by: Subramanian Mohan <subramanian.mohan@intel.com>
---
 drivers/pps/generators/Kconfig       |  16 ++
 drivers/pps/generators/Makefile      |   1 +
 drivers/pps/generators/pps_gen_tio.c | 272 +++++++++++++++++++++++++++
 3 files changed, 289 insertions(+)
 create mode 100644 drivers/pps/generators/pps_gen_tio.c

diff --git a/drivers/pps/generators/Kconfig b/drivers/pps/generators/Kconfig
index cd94bf3bfaf2..b3f340ed3163 100644
--- a/drivers/pps/generators/Kconfig
+++ b/drivers/pps/generators/Kconfig
@@ -31,4 +31,20 @@ config PPS_GENERATOR_PARPORT
 	  utilizes STROBE pin of a parallel port to send PPS signals. It uses
 	  parport abstraction layer and hrtimers to precisely control the signal.
 
+config PPS_GENERATOR_TIO
+	tristate "TIO PPS signal generator"
+	depends on X86 && CPU_SUP_INTEL
+	help
+	  If you say yes here you get support for a PPS TIO signal generator
+	  which generates a pulse at a prescribed time based on the system clock.
+	  It uses time translation and hrtimers to precisely generate a pulse.
+	  This hardware is present on 2019 and newer Intel CPUs. However, this
+	  driver is not useful without adding highly specialized hardware outside
+	  the Linux system to observe these pulses.
+
+	  To compile this driver as a module, choose M here: the module
+	  will be called pps_gen_tio.
+
+	  If unsure, say N.
+
 endif # PPS_GENERATOR
diff --git a/drivers/pps/generators/Makefile b/drivers/pps/generators/Makefile
index dc1aa5a4688b..e109920e8a2d 100644
--- a/drivers/pps/generators/Makefile
+++ b/drivers/pps/generators/Makefile
@@ -8,5 +8,6 @@ obj-$(CONFIG_PPS_GENERATOR)	:= pps_gen_core.o
 
 obj-$(CONFIG_PPS_GENERATOR_DUMMY)   += pps_gen-dummy.o
 obj-$(CONFIG_PPS_GENERATOR_PARPORT) += pps_gen_parport.o
+obj-$(CONFIG_PPS_GENERATOR_TIO)     += pps_gen_tio.o
 
 ccflags-$(CONFIG_PPS_DEBUG) := -DDEBUG
diff --git a/drivers/pps/generators/pps_gen_tio.c b/drivers/pps/generators/pps_gen_tio.c
new file mode 100644
index 000000000000..6c46b46c66cd
--- /dev/null
+++ b/drivers/pps/generators/pps_gen_tio.c
@@ -0,0 +1,272 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Intel PPS signal Generator Driver
+ *
+ * Copyright (C) 2024 Intel Corporation
+ */
+
+#include <linux/bitfield.h>
+#include <linux/bits.h>
+#include <linux/cleanup.h>
+#include <linux/container_of.h>
+#include <linux/device.h>
+#include <linux/hrtimer.h>
+#include <linux/io-64-nonatomic-hi-lo.h>
+#include <linux/mod_devicetable.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/pps_gen_kernel.h>
+#include <linux/timekeeping.h>
+#include <linux/types.h>
+
+#include <asm/cpu_device_id.h>
+
+#define TIOCTL			0x00
+#define TIOCOMPV		0x10
+#define TIOEC			0x30
+
+/* Control Register */
+#define TIOCTL_EN			BIT(0)
+#define TIOCTL_DIR			BIT(1)
+#define TIOCTL_EP			GENMASK(3, 2)
+#define TIOCTL_EP_RISING_EDGE		FIELD_PREP(TIOCTL_EP, 0)
+#define TIOCTL_EP_FALLING_EDGE		FIELD_PREP(TIOCTL_EP, 1)
+#define TIOCTL_EP_TOGGLE_EDGE		FIELD_PREP(TIOCTL_EP, 2)
+
+/* Safety time to set hrtimer early */
+#define SAFE_TIME_NS			(10 * NSEC_PER_MSEC)
+
+#define MAGIC_CONST			(NSEC_PER_SEC - SAFE_TIME_NS)
+#define ART_HW_DELAY_CYCLES		2
+
+struct pps_tio {
+	struct pps_gen_source_info gen_info;
+	struct pps_gen_device *pps_gen;
+	struct hrtimer timer;
+	void __iomem *base;
+	u32 prev_count;
+	spinlock_t lock;
+	struct device *dev;
+};
+
+static inline u32 pps_tio_read(u32 offset, struct pps_tio *tio)
+{
+	return readl(tio->base + offset);
+}
+
+static inline void pps_ctl_write(u32 value, struct pps_tio *tio)
+{
+	writel(value, tio->base + TIOCTL);
+}
+
+/*
+ * For COMPV register, It's safer to write
+ * higher 32-bit followed by lower 32-bit
+ */
+static inline void pps_compv_write(u64 value, struct pps_tio *tio)
+{
+	hi_lo_writeq(value, tio->base + TIOCOMPV);
+}
+
+static inline ktime_t first_event(struct pps_tio *tio)
+{
+	return ktime_set(ktime_get_real_seconds() + 1, MAGIC_CONST);
+}
+
+static u32 pps_tio_disable(struct pps_tio *tio)
+{
+	u32 ctrl;
+
+	ctrl = pps_tio_read(TIOCTL, tio);
+	pps_compv_write(0, tio);
+
+	ctrl &= ~TIOCTL_EN;
+	pps_ctl_write(ctrl, tio);
+	tio->pps_gen->enabled = false;
+	tio->prev_count = 0;
+	return ctrl;
+}
+
+static void pps_tio_enable(struct pps_tio *tio)
+{
+	u32 ctrl;
+
+	ctrl = pps_tio_read(TIOCTL, tio);
+	ctrl |= TIOCTL_EN;
+	pps_ctl_write(ctrl, tio);
+	tio->pps_gen->enabled = true;
+}
+
+static void pps_tio_direction_output(struct pps_tio *tio)
+{
+	u32 ctrl;
+
+	ctrl = pps_tio_disable(tio);
+
+	/*
+	 * We enable the device, be sure that the
+	 * 'compare' value is invalid
+	 */
+	pps_compv_write(0, tio);
+
+	ctrl &= ~(TIOCTL_DIR | TIOCTL_EP);
+	ctrl |= TIOCTL_EP_TOGGLE_EDGE;
+	pps_ctl_write(ctrl, tio);
+	pps_tio_enable(tio);
+}
+
+static bool pps_generate_next_pulse(ktime_t expires, struct pps_tio *tio)
+{
+	u64 art;
+
+	if (!ktime_real_to_base_clock(expires, CSID_X86_ART, &art)) {
+		pps_tio_disable(tio);
+		return false;
+	}
+
+	pps_compv_write(art - ART_HW_DELAY_CYCLES, tio);
+	return true;
+}
+
+static enum hrtimer_restart hrtimer_callback(struct hrtimer *timer)
+{
+	ktime_t expires, now;
+	u32 event_count;
+	struct pps_tio *tio = container_of(timer, struct pps_tio, timer);
+
+	guard(spinlock)(&tio->lock);
+
+	/*
+	 * Check if any event is missed.
+	 * If an event is missed, TIO will be disabled.
+	 */
+	event_count = pps_tio_read(TIOEC, tio);
+	if (tio->prev_count && tio->prev_count == event_count)
+		goto err;
+	tio->prev_count = event_count;
+
+	expires = hrtimer_get_expires(timer);
+
+	now = ktime_get_real();
+	if (now - expires >= SAFE_TIME_NS)
+		goto err;
+
+	tio->pps_gen->enabled = pps_generate_next_pulse(expires + SAFE_TIME_NS, tio);
+	if (!tio->pps_gen->enabled)
+		return HRTIMER_NORESTART;
+
+	hrtimer_forward(timer, now, NSEC_PER_SEC / 2);
+	return HRTIMER_RESTART;
+
+err:
+	dev_err(tio->dev, "Event missed, Disabling Timed I/O");
+	pps_tio_disable(tio);
+	pps_gen_event(tio->pps_gen, PPS_GEN_EVENT_MISSEDPULSE, NULL);
+	return HRTIMER_NORESTART;
+}
+
+static int pps_tio_gen_enable(struct pps_gen_device *pps_gen, bool enable)
+{
+	struct pps_tio *tio = container_of(pps_gen->info, struct pps_tio, gen_info);
+
+	if (!timekeeping_clocksource_has_base(CSID_X86_ART)) {
+		dev_err_once(tio->dev, "PPS cannot be used as clock is not related to ART");
+		return -ENODEV;
+	}
+
+	guard(spinlock_irqsave)(&tio->lock);
+	if (enable && !pps_gen->enabled) {
+		pps_tio_direction_output(tio);
+		hrtimer_start(&tio->timer, first_event(tio), HRTIMER_MODE_ABS);
+	} else if (!enable && pps_gen->enabled) {
+		hrtimer_cancel(&tio->timer);
+		pps_tio_disable(tio);
+	}
+
+	return 0;
+}
+
+static int pps_tio_get_time(struct pps_gen_device *pps_gen,
+			    struct timespec64 *time)
+{
+	struct system_time_snapshot snap;
+
+	ktime_get_snapshot(&snap);
+	*time = ktime_to_timespec64(snap.real);
+
+	return 0;
+}
+
+static int pps_gen_tio_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct pps_tio *tio;
+
+	if (!(cpu_feature_enabled(X86_FEATURE_TSC_KNOWN_FREQ) &&
+	      cpu_feature_enabled(X86_FEATURE_ART))) {
+		dev_warn(dev, "TSC/ART is not enabled");
+		return -ENODEV;
+	}
+
+	tio = devm_kzalloc(dev, sizeof(*tio), GFP_KERNEL);
+	if (!tio)
+		return -ENOMEM;
+
+	tio->gen_info.use_system_clock = true;
+	tio->gen_info.enable = pps_tio_gen_enable;
+	tio->gen_info.get_time = pps_tio_get_time;
+	tio->gen_info.owner = THIS_MODULE;
+
+	tio->pps_gen = pps_gen_register_source(&tio->gen_info);
+	if (IS_ERR(tio->pps_gen))
+		return PTR_ERR(tio->pps_gen);
+
+	tio->dev = dev;
+	tio->base = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(tio->base))
+		return PTR_ERR(tio->base);
+
+	pps_tio_disable(tio);
+	hrtimer_init(&tio->timer, CLOCK_REALTIME, HRTIMER_MODE_ABS);
+	tio->timer.function = hrtimer_callback;
+	spin_lock_init(&tio->lock);
+	platform_set_drvdata(pdev, &tio);
+
+	return 0;
+}
+
+static void pps_gen_tio_remove(struct platform_device *pdev)
+{
+	struct pps_tio *tio = platform_get_drvdata(pdev);
+
+	hrtimer_cancel(&tio->timer);
+	pps_tio_disable(tio);
+	pps_gen_unregister_source(tio->pps_gen);
+}
+
+static const struct acpi_device_id intel_pmc_tio_acpi_match[] = {
+	{ "INTC1021" },
+	{ "INTC1022" },
+	{ "INTC1023" },
+	{ "INTC1024" },
+	{}
+};
+MODULE_DEVICE_TABLE(acpi, intel_pmc_tio_acpi_match);
+
+static struct platform_driver pps_gen_tio_driver = {
+	.probe          = pps_gen_tio_probe,
+	.remove         = pps_gen_tio_remove,
+	.driver         = {
+		.name                   = "intel-pps-gen-tio",
+		.acpi_match_table       = intel_pmc_tio_acpi_match,
+	},
+};
+module_platform_driver(pps_gen_tio_driver);
+
+MODULE_AUTHOR("Christopher Hall <christopher.s.hall@intel.com>");
+MODULE_AUTHOR("Lakshmi Sowjanya D <lakshmi.sowjanya.d@intel.com>");
+MODULE_AUTHOR("Pandith N <pandith.n@intel.com>");
+MODULE_AUTHOR("Thejesh Reddy T R <thejesh.reddy.t.r@intel.com>");
+MODULE_AUTHOR("Subramanian Mohan <subramanian.mohan@intel.com>");
+MODULE_DESCRIPTION("Intel PMC Time-Aware IO Generator Driver");
+MODULE_LICENSE("GPL");
-- 
2.35.3

[PATCH v14 3/4] Documentation: driver-api: pps: Add Intel Timed I/O PPS generator

[subramanian.mohan]

From: Subramanian Mohan <subramanian.mohan@intel.com>

Add Intel Timed I/O PPS usage instructions.

Co-developed-by: Pandith N <pandith.n@intel.com>
Signed-off-by: Pandith N <pandith.n@intel.com>
Signed-off-by: Lakshmi Sowjanya D <lakshmi.sowjanya.d@intel.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Rodolfo Giometti <giometti@enneenne.com>
Signed-off-by: Subramanian Mohan <subramanian.mohan@intel.com>
---
 Documentation/driver-api/pps.rst | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/Documentation/driver-api/pps.rst b/Documentation/driver-api/pps.rst
index 04f1b88778fc..598729f9cd27 100644
--- a/Documentation/driver-api/pps.rst
+++ b/Documentation/driver-api/pps.rst
@@ -285,3 +285,27 @@ delay between assert and clear edge as small as possible to reduce system
 latencies. But if it is too small slave won't be able to capture clear edge
 transition. The default of 30us should be good enough in most situations.
 The delay can be selected using 'delay' pps_gen_parport module parameter.
+
+
+Intel Timed I/O PPS signal generator
+------------------------------------
+
+Intel Timed I/O is a high precision device, present on 2019 and newer Intel
+CPUs, that can generate PPS signals.
+
+Timed I/O and system time are both driven by same hardware clock. The signal
+is generated with a precision of ~20 nanoseconds. The generated PPS signal
+is used to synchronize an external device with system clock. For example,
+it can be used to share your clock with a device that receives PPS signal,
+generated by Timed I/O device. There are dedicated Timed I/O pins to deliver
+the PPS signal to an external device.
+
+Usage of Intel Timed I/O as PPS generator:
+
+Start generating PPS signal::
+
+        $echo 1 > /sys/class/pps-gen/pps-genx/enable
+
+Stop generating PPS signal::
+
+        $echo 0 > /sys/class/pps-gen/pps-genx/enable
-- 
2.35.3

[PATCH v14 4/4] ABI: pps: Add ABI documentation for Intel TIO

[subramanian.mohan]

From: Subramanian Mohan <subramanian.mohan@intel.com>

Document sysfs interface for Intel Timed I/O PPS driver.

Signed-off-by: Lakshmi Sowjanya D <lakshmi.sowjanya.d@intel.com>
Signed-off-by: Subramanian Mohan <subramanian.mohan@intel.com>
---
 Documentation/ABI/testing/sysfs-pps-gen-tio | 6 ++++++
 MAINTAINERS                                 | 1 +
 2 files changed, 7 insertions(+)
 create mode 100644 Documentation/ABI/testing/sysfs-pps-gen-tio

diff --git a/Documentation/ABI/testing/sysfs-pps-gen-tio b/Documentation/ABI/testing/sysfs-pps-gen-tio
new file mode 100644
index 000000000000..3c34ff17a335
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-pps-gen-tio
@@ -0,0 +1,6 @@
+What:		/sys/class/pps-gen/pps-genx/enable
+Date:		April 2025
+KernelVersion:	6.15
+Contact:	Subramanian Mohan<subramanian.mohan@intel.com>
+Description:
+		Enable or disable PPS TIO generator output.
diff --git a/MAINTAINERS b/MAINTAINERS
index 25c86f47353d..d4280facbe51 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -18916,6 +18916,7 @@ S:	Maintained
 W:	http://wiki.enneenne.com/index.php/LinuxPPS_support
 F:	Documentation/ABI/testing/sysfs-pps
 F:	Documentation/ABI/testing/sysfs-pps-gen
+F:	Documentation/ABI/testing/sysfs-pps-gen-tio
 F:	Documentation/devicetree/bindings/pps/pps-gpio.yaml
 F:	Documentation/driver-api/pps.rst
 F:	drivers/pps/
-- 
2.35.3

Re: [PATCH v14 1/4] drivers pps/generators: replace copy of pps-gen info struct with const pointer

[Andy Shevchenko]

On Fri, Feb 14, 2025 at 02:37:52PM +0530, subramanian.mohan@intel.com wrote:
> From: Subramanian Mohan <subramanian.mohan@intel.com>
> 
> Some PPS generator drivers may need to retrieve a pointer to their
> internal data while executing the PPS generator enable() method.
> 
> During the driver registration the pps_gen_device pointer is returned
> from the framework, and for that reason, there is difficulty in
> getting generator driver data back in the enable function. We won't be
> able to use container_of macro as it results in static assert, and we
> might end up in using static pointer.
> 
> To solve the issue and to get back the generator driver data back, we
> should not copy the struct pps_gen_source_info within the struct
> pps_gen_device during the registration stage, but simply save the
> pointer of the driver one. In this manner, driver may get a pointer
> to their internal data as shown below:
> 
> struct pps_gen_foo_data_s {
>         ...
> 	struct pps_gen_source_info gen_info;
> 	struct pps_gen_device *pps_gen;
> 	...
> };
> 
> static int __init pps_gen_foo_init(void)
> {
>         struct pps_gen_foo_data_s *foo;
> 	...
>         foo->pps_gen = pps_gen_register_source(&foo->gen_info);
> 	...
> }
> 
> Then, in the enable() method, we can retrieve the pointer to the main
> struct by using the code below:
> 
> static int pps_gen_foo_enable(struct pps_gen_device *pps_gen, bool enable)
> {
>         struct pps_gen_foo_data_s *foo = container_of(pps_gen->info,
> 						struct pps_gen_foo_data_s, gen_info);
>         ...
> }

Shouldn't Subject start with "pps: generators: ..."?

With that fixed,
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

-- 
With Best Regards,
Andy Shevchenko

RE: [PATCH v14 1/4] drivers pps/generators: replace copy of pps-gen info struct with const pointer

[Mohan, Subramanian]

> -----Original Message-----
> From: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> Sent: Friday, February 14, 2025 8:25 PM
> To: Mohan, Subramanian <subramanian.mohan@intel.com>
> Cc: linux-kernel@vger.kernel.org; linux-doc@vger.kernel.org;
> gregkh@linuxfoundation.org; giometti@enneenne.com; tglx@linutronix.de;
> corbet@lwn.net; Dong, Eddie <eddie.dong@intel.com>; Hall, Christopher S
> <christopher.s.hall@intel.com>; N, Pandith <pandith.n@intel.com>; T R,
> Thejesh Reddy <thejesh.reddy.t.r@intel.com>; Zage, David
> <david.zage@intel.com>; Chinnadurai, Srinivasan
> <srinivasan.chinnadurai@intel.com>
> Subject: Re: [PATCH v14 1/4] drivers pps/generators: replace copy of pps-gen
> info struct with const pointer
> 
> On Fri, Feb 14, 2025 at 02:37:52PM +0530, subramanian.mohan@intel.com
> wrote:
> > From: Subramanian Mohan <subramanian.mohan@intel.com>
> >
> > Some PPS generator drivers may need to retrieve a pointer to their
> > internal data while executing the PPS generator enable() method.
> >
> > During the driver registration the pps_gen_device pointer is returned
> > from the framework, and for that reason, there is difficulty in
> > getting generator driver data back in the enable function. We won't be
> > able to use container_of macro as it results in static assert, and we
> > might end up in using static pointer.
> >
> > To solve the issue and to get back the generator driver data back, we
> > should not copy the struct pps_gen_source_info within the struct
> > pps_gen_device during the registration stage, but simply save the
> > pointer of the driver one. In this manner, driver may get a pointer to
> > their internal data as shown below:
> >
> > struct pps_gen_foo_data_s {
> >         ...
> > 	struct pps_gen_source_info gen_info;
> > 	struct pps_gen_device *pps_gen;
> > 	...
> > };
> >
> > static int __init pps_gen_foo_init(void) {
> >         struct pps_gen_foo_data_s *foo;
> > 	...
> >         foo->pps_gen = pps_gen_register_source(&foo->gen_info);
> > 	...
> > }
> >
> > Then, in the enable() method, we can retrieve the pointer to the main
> > struct by using the code below:
> >
> > static int pps_gen_foo_enable(struct pps_gen_device *pps_gen, bool
> > enable) {
> >         struct pps_gen_foo_data_s *foo = container_of(pps_gen->info,
> > 						struct pps_gen_foo_data_s,
> gen_info);
> >         ...
> > }
> 
> Shouldn't Subject start with "pps: generators: ..."?
> 
> With that fixed,
> Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

Sure Andy will modify the subject line as suggested and add Reviewed-by tag, Will resend v15 accordingly.

Thanks,
Subbu

> 
> --
> With Best Regards,
> Andy Shevchenko
>