mbox series

[0/2] Fix debugfs register access while suspended

Message ID 20200124132957.15769-1-geert+renesas@glider.be
Headers show
Series Fix debugfs register access while suspended | expand

Message

Geert Uytterhoeven Jan. 24, 2020, 1:29 p.m. UTC 
Hi all,

While comparing register values read from debugfs files under
/sys/kernel/debug/ccree/, I noticed some oddities.
Apparently there is no guarantee these registers are read from the
device while it is resumed.  This may lead to bogus values, or crashes
and lock-ups.

This patch series:
  1. Allows debugfs_create_regset32() to be used for devices whose
     registers must be accessed when resumed,
  2. Fixes the CCREE driver to make use of this.

I have identified several other drivers that may be affected (i.e.
using debugfs_create_regset32() and pm_runtime_*()):
  - drivers/gpu/drm/msm/disp/dpu1
  - drivers/usb/dwc3
  - drivers/usb/host/ehci-omap.c
  - drivers/usb/host/ehci-tegra.c
  - drivers/usb/host/ohci-platform.c
  - drivers/usb/host/xhci.c
  - drivers/usb/host/xhci-dbgcap.c
  - drivers/usb/host/xhci-histb.c
  - drivers/usb/host/xhci-hub.c
  - drivers/usb/host/xhci-mtk.c
  - drivers/usb/host/xhci-pci.c
  - drivers/usb/host/xhci-plat.c
  - drivers/usb/host/xhci-tegra.c
  - drivers/usb/mtu3
  - drivers/usb/musb

Some of these call pm_runtime_forbid(), but given the comment "users
should enable runtime pm using power/control in sysfs", this can be
overridden from userspace, so these are unsafe, too?

Thanks for your comments!

Geert Uytterhoeven (2):
  debugfs: regset32: Add Runtime PM support
  crypto: ccree - fix debugfs register access while suspended

 drivers/crypto/ccree/cc_debugfs.c | 2 ++
 fs/debugfs/file.c                 | 8 ++++++++
 include/linux/debugfs.h           | 1 +
 3 files changed, 11 insertions(+)