ionic: Expose more port stats to ethtool

The primary aim of this patchset is to support the reporting of new port
statistics (and one old one) that firmware sends to the driver; these
include general FEC codeword stats and the FEC histogram. A scheme for
these extra stats is introduced in order to prevent devices that don't
support these new statistics from unconditionally setting them or
reporting them in ethtool.

---
v4:
- A big addition is a new scheme where the driver will only report the
  new statistics supported by firmware if the firmware sets the statistic
  value to something that isn't invalid; more details in patch 3, and this
  is used in patch 5 to prevent FEC stats from being unconditionally
  reported on devices/firmware versions that don't support these stats.
- The link_down_count from firmware mentioned in v2 was moved back to an
  entry in the general ethtool statistics; the existing driver-calculated
  value for the ethtool ext link is more appropriate due to the firmware
  value being a small size and not resetting between driver loads.
- Add netdev_err_once() call recommended by Sashiko for ethtool handler
- Drop devcmd retry logic patch from previous versions for now;
  explicitly include Brett's patch from another patchset to fix the
  ionic_get_link_ext_stats() PF/VF check

v3:
Address issues mostly found by Sashiko:
- Fix potential return of uninitialized variable in __ionic_dev_cmd_wait()
- Fix bounds of wait in __ionic_dev_cmd_wait() to prevent function from
  giving up prematurely now that the wait period has changed
- Add NULL check to ionic_get_link_ext_stats(), following the example set by
  ionic_get_link_ksettings()
- Add missing le16_to_cpu() when copying link_down_count from firmware

v2:
- Add missing cpu_to_le64() to FEC histogram stat assignment
- Remove unused pb_stats field that's replaced by the new FEC/extra stats
- Replace ethtool ext link stat with firmware stat instead of adding
  the firmware stat to general ethtool statistics; remove old driver
  calculated stat
- Add explanation for what EAGAIN return value could be used for in
  commit message

Brett Creeley (1):
  ionic: Fix check in ionic_get_link_ext_stats

Eric Joyner (4):
  ionic: Update ionic_if.h with new extra port stats
  ionic: Report "rx_bits_phy" stat to ethtool
  ionic: Report "link_down_events_phy" in ethtool statistics
  ionic: Add .get_fec_stats ethtool handler

 .../net/ethernet/pensando/ionic/ionic_dev.h   |  1 +
 .../ethernet/pensando/ionic/ionic_ethtool.c   | 83 ++++++++++++++++++-
 .../net/ethernet/pensando/ionic/ionic_if.h    | 39 +++------
 .../net/ethernet/pensando/ionic/ionic_main.c  |  6 ++
 .../net/ethernet/pensando/ionic/ionic_stats.c | 64 +++++++++++++-
 5 files changed, 164 insertions(+), 29 deletions(-)


base-commit: 93790c374b9d77f3db15786d7d432872d92751cf
-- 
2.17.1