Skip to content

Commit d469271

Browse files
committed
video: Correct limitations of odd pixel timings for Pi 5
Odd timings have been supported on Pi 5 since raspberrypi/linux#5679
1 parent 14b1572 commit d469271

File tree

2 files changed

+9
-5
lines changed

2 files changed

+9
-5
lines changed

documentation/asciidoc/computers/config_txt/video.adoc

Lines changed: 8 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -4,17 +4,21 @@
44

55
To control HDMI settings, use the xref:configuration.adoc#set-resolution-and-rotation[Screen Configuration utility] or xref:configuration.adoc#set-the-kms-display-mode[KMS video settings] in `cmdline.txt`.
66

7-
==== HDMI Pipeline for Raspberry Pi 4 and 5
7+
==== HDMI Pipeline for Raspberry Pi 4
88

9-
In order to support dual displays and modes up to 4k60, the Raspberry Pi 4 and 5 generate 2 output pixels for every clock cycle.
9+
In order to support dual displays and modes up to 4k60, the Raspberry Pi 4 generate 2 output pixels for every clock cycle.
1010

1111
Every HDMI mode has a list of timings that control all the parameters around sync pulse durations. These are typically defined via a pixel clock, and then a number of active pixels, a front porch, sync pulse, and back porch for each of the horizontal and vertical directions.
1212

13-
Running everything at 2 pixels per clock means that the Raspberry Pi 4 and 5 cannot support a timing where _any_ of the horizontal timings are not divisible by 2. The firmware and Linux kernel filter out any mode that does not fulfil this criteria.
13+
Running everything at 2 pixels per clock means that the Raspberry Pi 4 cannot support a timing where _any_ of the horizontal timings are not divisible by 2. The firmware and Linux kernel filter out any mode that does not fulfil this criteria.
1414

1515
There is only one incompatible mode in the CEA and DMT standards: DMT mode 81, 1366x768 @ 60Hz. This mode has odd-numbered values for the horizontal sync and back porch timings and a width that indivisible by 8.
1616

17-
If your monitor has this resolution, Raspberry Pi 4 or 5 automatically drops down to the next mode advertised by the monitor; typically 1280x720.
17+
If your monitor has this resolution, Raspberry Pi 4 automatically drops down to the next mode advertised by the monitor; typically 1280x720.
18+
19+
==== HDMI Pipeline for Raspberry Pi 5
20+
21+
While Pi 5 also works at 2 output pixels per clock cycle, it has special handling for odd timings and can handle these modes directly.
1822

1923
=== Composite video mode
2024

documentation/asciidoc/computers/legacy_config_txt/video.adoc

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -1299,7 +1299,7 @@ These values are valid if `hdmi_group=2` (DMT):
12991299
| 1366x768
13001300
| 60Hz
13011301
| 16:9
1302-
| xref:config_txt.adoc#hdmi-pipeline-for-raspberry-pi-4-and-5[NOT on Raspberry Pi 4 and 5]
1302+
| xref:config_txt.adoc#hdmi-pipeline-for-raspberry-pi-4[NOT on Raspberry Pi 4]
13031303

13041304
| 82
13051305
| 1920x1080

0 commit comments

Comments
 (0)