linux-kernel - [PATCH v12 2/3] Documentation: driver-api: pps: Add Intel Timed I/O PPS generator

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Message-Id: <20240823070109.27815-3-subramanian.mohan@intel.com>
Date: Fri, 23 Aug 2024 12:31:07 +0530
From: subramanian.mohan@...el.com
To: gregkh@...uxfoundation.org,
	tglx@...utronix.de,
	giometti@...eenne.com,
	corbet@....net,
	linux-kernel@...r.kernel.org,
	linux-doc@...r.kernel.org
Cc: andriy.shevchenko@...ux.intel.com,
	eddie.dong@...el.com,
	christopher.s.hall@...el.com,
	pandith.n@...el.com,
	thejesh.reddy.t.r@...el.com,
	david.zage@...el.com,
	srinivasan.chinnadurai@...el.com,
	subramanian.mohan@...el.com
Subject: [PATCH v12 2/3] Documentation: driver-api: pps: Add Intel Timed I/O PPS generator

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

Add Intel Timed I/O PPS usage instructions.

Co-developed-by: Pandith N <pandith.n@...el.com>
Signed-off-by: Pandith N <pandith.n@...el.com>
Signed-off-by: Lakshmi Sowjanya D <lakshmi.sowjanya.d@...el.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Acked-by: Rodolfo Giometti <giometti@...eenne.com>
Signed-off-by: Subramanian Mohan <subramanian.mohan@...el.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 78dded03e5d8..75f7b094f963 100644
--- a/Documentation/driver-api/pps.rst
+++ b/Documentation/driver-api/pps.rst
@@ -246,3 +246,27 @@ 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/devices/platform/INTCxxxx\:00/enable
+
+Stop generating PPS signal::
+
+        $echo 0 > /sys/devices/platform/INTCxxxx\:00/enable
-- 
2.35.3