linux-kernel - [PATCH v5 4/4] media: admin-guide: mgb4: Outputs DV timings documentation update

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Date: Fri, 26 Apr 2024 16:16:19 +0200
From: tumic@...see.org
To: Mauro Carvalho Chehab <mchehab@...nel.org>,
	Hans Verkuil <hverkuil@...all.nl>
Cc: linux-media@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Martin Tůma <martin.tuma@...iteqautomotive.com>
Subject: [PATCH v5 4/4] media: admin-guide: mgb4: Outputs DV timings documentation update

From: Martin Tůma <martin.tuma@...iteqautomotive.com>

Properly document the function of the mgb4 output "frame_rate" sysfs parameter
and update the default DV timings values according to the latest code changes.

Signed-off-by: Martin Tůma <martin.tuma@...iteqautomotive.com>
---
 Documentation/admin-guide/media/mgb4.rst | 23 ++++++++++++++---------
 1 file changed, 14 insertions(+), 9 deletions(-)

diff --git a/Documentation/admin-guide/media/mgb4.rst b/Documentation/admin-guide/media/mgb4.rst
index e434d4a9eeb3..b9da127c074d 100644
--- a/Documentation/admin-guide/media/mgb4.rst
+++ b/Documentation/admin-guide/media/mgb4.rst
@@ -227,8 +227,13 @@ Common FPDL3/GMSL output parameters
     open.*
 
 **frame_rate** (RW):
-    Output video frame rate in frames per second. The default frame rate is
-    60Hz.
+    Output video signal frame rate limit in frames per second. Due to
+    the limited output pixel clock steps, the card can not always generate
+    a frame rate perfectly matching the value required by the connected display.
+    Using this parameter one can limit the frame rate by "crippling" the signal
+    so that the lines are not equal (the porches of the last line differ) but
+    the signal appears like having the exact frame rate to the connected display.
+    The default frame rate limit is 60Hz.
 
 **hsync_polarity** (RW):
     HSYNC signal polarity.
@@ -253,33 +258,33 @@ Common FPDL3/GMSL output parameters
     and there is a non-linear stepping between two consecutive allowed
     frequencies. The driver finds the nearest allowed frequency to the given
     value and sets it. When reading this property, you get the exact
-    frequency set by the driver. The default frequency is 70000kHz.
+    frequency set by the driver. The default frequency is 61150kHz.
 
     *Note: This parameter can not be changed while the output v4l2 device is
     open.*
 
 **hsync_width** (RW):
-    Width of the HSYNC signal in pixels. The default value is 16.
+    Width of the HSYNC signal in pixels. The default value is 40.
 
 **vsync_width** (RW):
-    Width of the VSYNC signal in video lines. The default value is 2.
+    Width of the VSYNC signal in video lines. The default value is 20.
 
 **hback_porch** (RW):
     Number of PCLK pulses between deassertion of the HSYNC signal and the first
-    valid pixel in the video line (marked by DE=1). The default value is 32.
+    valid pixel in the video line (marked by DE=1). The default value is 50.
 
 **hfront_porch** (RW):
     Number of PCLK pulses between the end of the last valid pixel in the video
     line (marked by DE=1) and assertion of the HSYNC signal. The default value
-    is 32.
+    is 50.
 
 **vback_porch** (RW):
     Number of video lines between deassertion of the VSYNC signal and the video
-    line with the first valid pixel (marked by DE=1). The default value is 2.
+    line with the first valid pixel (marked by DE=1). The default value is 31.
 
 **vfront_porch** (RW):
     Number of video lines between the end of the last valid pixel line (marked
-    by DE=1) and assertion of the VSYNC signal. The default value is 2.
+    by DE=1) and assertion of the VSYNC signal. The default value is 30.
 
 FPDL3 specific input parameters
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-- 
2.44.0