Support gpio-poweroff driver to allow switching off power

[brycewilkins]

I tried to use the device tree GPIO binding gpio-poweroff to switch off power to the Raspberry Pi (via an on/off push-button controller) once the system reaches 'halt' state. Please see these links for info:
https://github.com/raspberrypi/linux/blob/rpi-4.0.y/Documentation/devicetree/bindings/gpio/gpio-poweroff.txt
and
https://www.raspberrypi.org/forums/viewtopic.php?f=107&t=113789.

It did not work because the standard Raspberry Pi configurations do not include the gpio-poweroff driver which must be enabled using the POWER_RESET and POWER_RESET_GPIO flags. I would like to request these additions.

I believe this would be an excellent feature to have support for as it will allow the RPi to actually switch off the power to a system it is controlling once it reaches a shutdown state. Currently the RPi enters a low-power shutdown state, but circuitry controlling the power (and anything connected to it) remains on.

As the gpio-poweroff driver would only be enabled by a device tree overlay it will not cause any conflict/incompatibility with existing systems.

Thank you!

[popcornmix]

Looks okay. Will add in next update.

[brycewilkins]

Fantastic! Thank you so much :) I'll be happy to test and report back when something is ready.

[popcornmix]

Can you try rpi-update. The options should be in.

[brycewilkins]

@popcornmix Unfortunately no success yet, here is what I did.

• Ran rpi-update and got the 4.0.6 kernel
• Recompile dt-blob.dts to /boot/dt-blob.bin
• Recompile my power-off DT overlay and put in /boot/overlays/

Please see my thread in raspberrypi.org forum for details (link in original post above).

I put an oscilloscope on GPIO 26 which I'm using as the power-off control signal. The pin goes high during boot when dt-blob.bin is loaded, but when I execute "shutdown -h now" or "poweroff" the pin remains high after the 'halt' state. (At the end of shutdown the Raspberry Pi green "disk activity" LED blinks a few times then stays off, while the red "power" LED stays on.)

The overlay seems to be loaded as I have directory /proc/device-tree/soc/gpio/power_ctrl/ and files within, but I wonder if the fragment@0 is correct.

How can I help to get it working? Thank you!

[popcornmix]

The options you requested appear to be present:

pi@raspberrypi:~ $ sudo modprobe configs 
pi@raspberrypi:~ $ zcat /proc/config.gz |grep POWER_RESET
CONFIG_POWER_RESET=y
# CONFIG_POWER_RESET_BRCMSTB is not set
CONFIG_POWER_RESET_GPIO=y
# CONFIG_POWER_RESET_GPIO_RESTART is not set
# CONFIG_POWER_RESET_LTC2952 is not set
# CONFIG_POWER_RESET_RESTART is not set
# CONFIG_POWER_RESET_SYSCON is not set

@pelwell may have some ideas.

[brycewilkins]

Thanks. I have the same output on my system.

Interesting that there is a config for LTC2952 which has some extra features compared to LTC2951 I am using. Seems like this should work.

[pelwell]

but I wonder if the fragment@0 is correct.

Good guess. I've commented on the thread.

[notro]

If I read this correctly, gpio-poweroff won't work because pm_power_off is already set in the platform file.

arch/arm/mach-bcm2708/bcm2708.c

void __init bcm2708_init(void)
{
...
    pm_power_off = bcm2708_power_off;

drivers/power/reset/gpio-poweroff.c

static int gpio_poweroff_probe(struct platform_device *pdev)
{
        bool input = false;

        /* If a pm_power_off function has already been added, leave it alone */
        if (pm_power_off != NULL) {
                dev_err(&pdev->dev,
                        "%s: pm_power_off function already registered",
                       __func__);
                return -EBUSY;
        }

[brycewilkins]

@notro : @pelwell noted that it should replace the standard pm_power_off handler - please see here

But as I've commented over in the thread, it's still not working...

[notro]

What does this return:

$ dmesg | grep poweroff

[pelwell]

I've got it working (with caveats) - I'm writing a response for the Forum.

[pelwell]

And you were correct (of course) about the existing pm_power_off handler.

[pelwell]

Thread updated. Gist here: https://gist.github.com/pelwell/e4c5662c331fcae1e707

[notro]

You could do:

if (!force && pm_power_off != NULL) {

[notro]

Or just remove the whole if clause, since pm_power_off will always be set in our repo.

[brycewilkins]

Thanks @pelwell @notro for getting to the root of the problem! I'd give it a try but not sure how to apply the patch...

[pelwell]

I've pushed the patch to the rpi-4.0.y branch. It will be in the next firmware release.

[brycewilkins]

That's really excellent news. I will post a message here when I test it. Thank you!

[popcornmix]

rpi-update firmware should contain @pelwell's patch

[brycewilkins]

It works perfectly! Thank you @popcornmix @pelwell @notro for all your help in adding this feature. No doubt a lot of people can make use of it. You guys are awesome!

I think this issue can be marked closed.