[PATCH 0/2] mmc: core: Fix Marvell WiFi reset by adding SDIO API to replug card

[Douglas Anderson <dianders@chromium.org>]

As talked about in the thread at:

http://lkml.kernel.org/r/CAD=FV=X7P2F1k_zwHc0mbtfk55-rucTz_GoDH=PL6zWqKYcpuw@mail.gmail.com

...when the Marvell WiFi card tries to reset itself it kills
Bluetooth.  It was observed that we could re-init the card properly by
unbinding / rebinding the host controller.  It was also observed that
in the downstream Chrome OS codebase the solution used was
mmc_remove_host() / mmc_add_host(), which is similar to the solution
in this series.

So far I've only done testing of this series using the reset test
source that can be simulated via sysfs.  Specifically I ran this test:

for i in $(seq 1000); do
  echo "LOOP $i --------"
  echo 1 > /sys/kernel/debug/mwifiex/mlan0/reset

  while true; do
    if ! ping -w15 -c1 "${GW}" >/dev/null 2>&1; then
      fail=$(( fail + 1 ))
      echo "Fail WiFi ${fail}"
      if [[ ${fail} == 3 ]]; then
        exit 1
      fi
    else
      fail=0
      break
    fi
  done

  hciconfig hci0 down
  sleep 1
  if ! hciconfig hci0 up; then
    echo "Fail BT"
    exit 1
  fi
done

I ran this several times and got several hundred iterations each
before a failure.  When I saw failures:

* Once I saw a "Fail BT"; manually resetting the card again fixed it.
  I didn't give it time to see if it would have detected this
  automatically.
* Once I saw the ping fail because (for some reason) my device only
  got an IPv6 address from my router and the IPv4 ping failed.  I
  changed my script to use 'ping6' to see if that would help.
* Once I saw the ping fail because the higher level network stack
  ("shill" in my case) seemed to crash.  A few minutes later the
  system recovered itself automatically.  https://crbug.com/984593 if
  you want more details.
* Sometimes while I was testing I saw "Fail WiFi 1" indicating a
  transitory failure.  Usually this was an association failure, but in
  one case I saw the device do "Firmware wakeup failed" after I
  triggered the reset.  This caused the driver to trigger a re-reset
  of itself which eventually recovered things.  This was good because
  it was an actual test of the normal reset flow (not the one
  triggered via sysfs).


Douglas Anderson (2):
  mmc: core: Add sdio_trigger_replug() API
  mwifiex: Make use of the new sdio_trigger_replug() API to reset

 drivers/mmc/core/core.c                     | 28 +++++++++++++++++++--
 drivers/mmc/core/sdio_io.c                  | 20 +++++++++++++++
 drivers/net/wireless/marvell/mwifiex/sdio.c | 14 +++--------
 include/linux/mmc/host.h                    | 15 ++++++++++-
 include/linux/mmc/sdio_func.h               |  2 ++
 5 files changed, 65 insertions(+), 14 deletions(-)

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2.22.0.510.g264f2c817a-goog