Document how link frequencies can be selected for the link-frequencies property. Signed-off-by: Sakari Ailus <sakari.ailus@xxxxxxxxxxxxxxx> --- Documentation/driver-api/media/camera-sensor.rst | 14 ++++++++++++++ .../userspace-api/media/drivers/camera-sensor.rst | 2 ++ 2 files changed, 16 insertions(+) diff --git a/Documentation/driver-api/media/camera-sensor.rst b/Documentation/driver-api/media/camera-sensor.rst index 6456145f96ed..0de5c86cbd1f 100644 --- a/Documentation/driver-api/media/camera-sensor.rst +++ b/Documentation/driver-api/media/camera-sensor.rst @@ -29,6 +29,20 @@ used in the system. Using another frequency may cause harmful effects elsewhere. Therefore only the pre-determined frequencies are configurable by the user. +On choosing link frequencies +~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Choosing link frequencies for a board is generally a part of the hardware design +process as one needs to ensure an EMC-safe frequency the sensor supports with +the given external clock frequency exists. On development systems this may be +less than an immediate concern, so more or less anything that sensor and the +rest of the applicable hardware supports can be used. + +If the sensor's PLL tree is not documented and all that is available are +register lists, even knowing the frequency a driver uses may be difficult. This +could still be :ref:`calculated from the number of lanes, sensor's output image +size, blanking values and frame rate <media_camera_raw_frame_interval>`. + ACPI ~~~~ diff --git a/Documentation/userspace-api/media/drivers/camera-sensor.rst b/Documentation/userspace-api/media/drivers/camera-sensor.rst index 919a50e8b9d9..7ffed5c2338c 100644 --- a/Documentation/userspace-api/media/drivers/camera-sensor.rst +++ b/Documentation/userspace-api/media/drivers/camera-sensor.rst @@ -54,6 +54,8 @@ less all modern raw camera sensors. The frame interval is calculated using the following equation:: +.. _media_camera_raw_frame_interval: + frame interval = (analogue crop width + horizontal blanking) * (analogue crop height + vertical blanking) / pixel rate -- 2.39.2
