[PATCH 00/11] ARM: bcm2835: Implement initial S2Idle for Raspberry Pi

Stefan Wahren
2024-06-30T15:37:52Z

This series implement the initial Suspend-To-Idle support for
the Raspberry Pi, which was a long time on my TODO list [1]. The
changes allow to suspend and resume the Raspberry Pi via debug UART.
The focus is on the BCM2835 SoC, because it's less complex than its
successors and have enough documentation.

The series is a loose collection of fixes and improvements.
So cherry-picking should be fine.

Test steps:
- configure debug console (pl011 or mini UART) as wakeup source
- send system to idle state

echo freeze > /sys/power/state

- wakeup system by console traffic

The implementation isn't perfect and contains workarounds like
patch 4 and 9. So there is still room for improvements, but
at least the system won't freeze forever as before [2].

Here are some figures for the Raspberry Pi 1 (without any
devices connected except of a debug UART):

running but CPU idle = 1.67 W
suspend to idle = 1.33 W

The series has been tested on the following platforms:
Raspberry Pi 1 B
Raspberry Pi 3 A+
Raspberry Pi 3 B+

Known issues:
- currently it's not possible to power down the USB domain [3]
- there seems to be an issue with the DWC2 suspend handling [4]

[1] - https://github.com/lategoodbye/rpi-zero/issues/9
[2] - https://bugzilla.redhat.com/show_bug.cgi?id=2283978
[3] - https://github.com/raspberrypi/firmware/issues/1894
[4] - https://lore.kernel.org/linux-usb/3fd0c2fb-4752-45b3-94eb-42352703e1fd@gmx.net/T/

Stefan Wahren (11):
firmware: raspberrypi: Improve timeout warning
mailbox: bcm2835: Fix timeout during suspend mode
pmdomain: raspberrypi-power: Adjust packet definition
pmdomain: raspberrypi-power: Avoid powering down USB
irqchip/bcm2835: Enable SKIP_SET_WAKE and MASK_ON_SUSPEND
drm/vc4: hdmi: Handle error case of pm_runtime_resume_and_get
drm/vc4: hdmi: Disable connector status polling during suspend
usb: dwc2: debugfs: Print parameter no_clock_gating
usb: dwc2: Skip clock gating on Broadcom SoCs
serial: 8250_bcm2835aux: add PM suspend/resume support
ARM: bcm2835_defconfig: Enable SUSPEND

arch/arm/configs/bcm2835_defconfig | 2 --
drivers/firmware/raspberrypi.c | 3 ++-
drivers/gpu/drm/vc4/vc4_hdmi.c | 18 +++++++++++++++++-
drivers/irqchip/irq-bcm2835.c | 4 +++-
drivers/mailbox/bcm2835-mailbox.c | 3 ++-
drivers/pmdomain/bcm/raspberrypi-power.c | 17 ++++++++++++-----
drivers/tty/serial/8250/8250_bcm2835aux.c | 23 +++++++++++++++++++++++
drivers/usb/dwc2/debugfs.c | 1 +
drivers/usb/dwc2/params.c | 1 +
9 files changed, 61 insertions(+), 11 deletions(-)

--
2.34.1