[PATCH v3 3/3] doc: ctucanfd: RX frames timestamping for platform devices

[Matej Vasilevski <matej.vasilevski@seznam.cz>]

Update the section about timestamping RX frames with instructions
how to enable it.

Signed-off-by: Matej Vasilevski <matej.vasilevski@seznam.cz>
---
 .../device_drivers/can/ctu/ctucanfd-driver.rst      | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/Documentation/networking/device_drivers/can/ctu/ctucanfd-driver.rst b/Documentation/networking/device_drivers/can/ctu/ctucanfd-driver.rst
index 40c92ea272af..05a7ce0c3d9e 100644
--- a/Documentation/networking/device_drivers/can/ctu/ctucanfd-driver.rst
+++ b/Documentation/networking/device_drivers/can/ctu/ctucanfd-driver.rst
@@ -386,8 +386,17 @@ The CTU CAN FD core reports the exact timestamp when the frame has been
 received. The timestamp is by default captured at the sample point of
 the last bit of EOF but is configurable to be captured at the SOF bit.
 The timestamp source is external to the core and may be up to 64 bits
-wide. At the time of writing, passing the timestamp from kernel to
-userspace is not yet implemented, but is planned in the future.
+wide.
+
+Both platform and PCI devices can report the timestamp.
+For platform devices, add another clock phandle for timestamping clock
+in device tree bindings. If you don't add another clock, the driver
+will assume the primary clock's frequency for timestamping.
+For PCI devices, the timestamping frequency is assumed to be equal to
+the bus frequency.
+
+Timestamp reporting is disabled by default, you have to enable it with
+SIOCSHWTSTAMP ioctl call first.
 
 Handling TX
 ~~~~~~~~~~~
-- 
2.25.1