RFC Disable e1000e power management if hardware error is detected

This is a trial patchset that aims to cope with an intermittently triggered hardware error during system resume.

On some platforms the NIC's hardware error was detected during resume from S3, causing the NIC to not fully initialize and remain in unstable state afterwards. As a consequence the system fails to suspend due to incorrect NIC status.

In theory if the NIC could not be initialized after resumed, it should not do system/runtime suspend/resume afterwards. There are two proposals to deal with this situation:

Either:
1. Each time before the NIC going to suspend, check the status of NIC by querying corresponding registers, bypass the suspend callback on this NIC if it's unstable.

Or:
2. During NIC resume, if the hardware error was detected, removes the NIC from power management list entirely.

Proposal 2 was chosen in this patch set because:
1. Proposal 1 requires that the driver queries the status
of the NIC in e1000e driver. However there seems to be
no specific registers for the e1000e to query the result
of NIC initialization.
2. Proposal 1 just bypass the suspend process but the power management framework is still aware of this NIC, which might bring potential issue in race condition.
3. Approach 2 is a clean solution and it is platform independent that, not only e1000e, but also other drivers could leverage this generic mechanism in the future.

Comments appreciated.

Chen Yu (4):
e1000e: save the return value of e1000e_reset()
PM: sleep: export device_pm_remove() for driver use
e1000e: Introduce workqueue to disable the power management
e1000e: Disable the power management if hardware error detected during
resume

 drivers/base/power/main.c                  |  1 +
 drivers/base/power/power.h                 |  8 -------
 drivers/net/ethernet/intel/e1000e/e1000.h  |  1 +
 drivers/net/ethernet/intel/e1000e/netdev.c | 27 ++++++++++++++++++----
 include/linux/pm.h                         | 12 ++++++++++
 5 files changed, 37 insertions(+), 12 deletions(-)

2.17.1