This is a note to let you know that I've just added the patch titled
media: dt-bindings/media/cec-gpio.txt: mention the CEC/HPD max voltages
to the 4.15-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...
The filename of the patch is: media-dt-bindings-media-cec-gpio.txt-mention-the-cec-hpd-max-voltages.patch and it can be found in the queue-4.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.
From dac15ed62dc9d7898d3695a3c393d6f712d66185 Mon Sep 17 00:00:00 2001
From: Hans Verkuil hverkuil@xs4all.nl Date: Sat, 16 Dec 2017 05:44:13 -0500 Subject: media: dt-bindings/media/cec-gpio.txt: mention the CEC/HPD max voltages
From: Hans Verkuil hverkuil@xs4all.nl
commit dac15ed62dc9d7898d3695a3c393d6f712d66185 upstream.
Mention the maximum voltages of the CEC and HPD lines. Since in the example these lines are connected to a Raspberry Pi and the Rpi GPIO lines are 3.3V it is a good idea to warn against directly connecting the HPD to the Raspberry Pi's GPIO line.
Signed-off-by: Hans Verkuil hans.verkuil@cisco.com Reviewed-by: Rob Herring robh@kernel.org Signed-off-by: Hans Verkuil hans.verkuil@cisco.com Signed-off-by: Mauro Carvalho Chehab mchehab@s-opensource.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- Documentation/devicetree/bindings/media/cec-gpio.txt | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-)
--- a/Documentation/devicetree/bindings/media/cec-gpio.txt +++ b/Documentation/devicetree/bindings/media/cec-gpio.txt @@ -4,6 +4,10 @@ The HDMI CEC GPIO module supports CEC im is hooked up to a pull-up GPIO line and - optionally - the HPD line is hooked up to another GPIO line.
+Please note: the maximum voltage for the CEC line is 3.63V, for the HPD +line it is 5.3V. So you may need some sort of level conversion circuitry +when connecting them to a GPIO line. + Required properties: - compatible: value must be "cec-gpio". - cec-gpios: gpio that the CEC line is connected to. The line should be @@ -21,7 +25,7 @@ the following property is optional:
Example for the Raspberry Pi 3 where the CEC line is connected to pin 26 aka BCM7 aka CE1 on the GPIO pin header and the HPD line is -connected to pin 11 aka BCM17: +connected to pin 11 aka BCM17 (some level shifter is needed for this!):
#include <dt-bindings/gpio/gpio.h>
Patches currently in stable-queue which might be from hverkuil@xs4all.nl are
queue-4.15/media-dt-bindings-media-cec-gpio.txt-mention-the-cec-hpd-max-voltages.patch