[PATCH V3 0/9] ARM: bcm2835: Implement initial S2Idle for Raspberry Pi

[Stefan Wahren]

This series implement the initial S2Idle 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 can be roughly separated in 3 parts:
 1. base patches (1, 9) which allows S2Idle support for BCM2835
 2. drm vc4 patches (2 - 6)  which implement S2Idle support
 3. dwc2 patches (7, 8) which handle BCM2835 specific issues

Cherry-picking of patches 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 DWC2 part based on an idea of Doug Anderson and its implementation
should be mostly finished now, but still RFC. The USB domain is now powered
down and the USB devices are still usable after resume. There is still room
for improvements, but at least the system won't freeze forever as before.

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
S2Idle               = 1.33 W

In comparison with HDMI & USB keyboard connected (but neither active
nor wakeup source):

running but CPU idle = 1.82 W
S2Idle               = 1.33 W

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

Changes in V3:
- added Reviewed-by & Acked-by from Florian & Maíra
- dropped applied pmdomain & bcm2835aux patches
- address comments by Maíra (patch 3 & 5)
- replace old USB recovery patch with canary approach [3], which should
  work with other platforms

Changes in V2:
- rebased against todays mainline
- added Reviewed-by from Florian
- added Acked-by from Minas
- dropped "irqchip/bcm2835: Enable SKIP_SET_WAKE and MASK_ON_SUSPEND"
  because it has been applied by Thomas Gleixner
- dropped "pmdomain: raspberrypi-power: Avoid powering down USB"
  because this workaround has been replaced by patch 14
- use drm_err_once instead of DRM_ERROR and return connector_status_unknown
  in patch 6
- add new patch in order to clean-up all DRM_ERROR
- add new patch to improve raspberrypi-power logging
- add new patch to simplify V3D clock retrieval
- add new patch 5 to avoid power down of wakeup devices
- add new patch 12 to avoid confusion about ACPI ID of BCM283x USB
- add new patch 8 & 10 which address the problem that HDMI
  is not functional after s2idle
- add more links and fix typo in patch 13
- add new WIP patch 14 which recover DWC2 register after power down
- take care of UART clock in patch 15 as commented by Florian
- use SYSTEM_SLEEP_PM_OPS in patch 15

[1] - https://github.com/lategoodbye/rpi-zero/issues/9
[2] - https://bugzilla.redhat.com/show_bug.cgi?id=2283978
[3] - https://lore.kernel.org/linux-usb/CAD=FV=W7sdi1+SHfhY6RrjK32r8iAGe4w+O_u5Sp982vgBU6EQ@mail.gmail.com/

Stefan Wahren (9):
  mailbox: bcm2835: Fix timeout during suspend mode
  drm/vc4: hdmi: Handle error case of pm_runtime_resume_and_get
  drm/vc4: Get the rid of DRM_ERROR()
  drm/vc4: hdmi: add PM suspend/resume support
  drm/vc4: v3d: simplify clock retrieval
  drm/vc4: v3d: add PM suspend/resume support
  usb: dwc2: Refactor backup/restore of registers
  usb: dwc2: Implement recovery after PM domain off
  ARM: bcm2835_defconfig: Enable SUSPEND

 arch/arm/configs/bcm2835_defconfig |   2 -
 drivers/gpu/drm/vc4/vc4_bo.c       |  14 ++--
 drivers/gpu/drm/vc4/vc4_dpi.c      |  14 ++--
 drivers/gpu/drm/vc4/vc4_dsi.c      |  32 +++++----
 drivers/gpu/drm/vc4/vc4_gem.c      |  11 ++--
 drivers/gpu/drm/vc4/vc4_hdmi.c     |  70 ++++++++++++++------
 drivers/gpu/drm/vc4/vc4_hvs.c      |   4 +-
 drivers/gpu/drm/vc4/vc4_irq.c      |   2 +-
 drivers/gpu/drm/vc4/vc4_v3d.c      |  26 +++-----
 drivers/gpu/drm/vc4/vc4_validate.c |   8 +--
 drivers/gpu/drm/vc4/vc4_vec.c      |  10 +--
 drivers/mailbox/bcm2835-mailbox.c  |   3 +-
 drivers/usb/dwc2/core.c            |   1 +
 drivers/usb/dwc2/core.h            |  14 ++++
 drivers/usb/dwc2/gadget.c          | 101 +++++++++++++++--------------
 drivers/usb/dwc2/hcd.c             |  99 ++++++++++++++--------------
 drivers/usb/dwc2/platform.c        |  38 +++++++++++
 17 files changed, 265 insertions(+), 184 deletions(-)

--
2.34.1