[PATCH 0/2] i2c: designware: Fix stuck master on multi-master buses

[Sarah Maedel <sarah.maedel@hetzner-cloud.de>]

Since v7.0, the DesignWare controller used for IPMI SSIF on Ampere
Altra (DW_apb_i2c 1.20a) can get stuck after "spurious STOP detected"
errors, and stays unusable until a power cycle.

Patch 1 limits the spurious STOP check to controllers without
IC_EMPTYFIFO_HOLD_MASTER, as suggested by David LaPorte [1].

Patch 2 lets __i2c_dw_disable() abort a stuck master on configurations
without IC_STAT_FOR_CLK_STRETCH, where it otherwise never recovers.

Patch 2 was tested on Altra by forcing the stuck state through
/dev/mem. With both patches applied, IPMI commands in a loop no
longer hang the controller on a Gigabyte and an ASRock Rack Altra
server.

Both patches were prepared with the help of an AI coding assistant
(Claude Opus 5.5). I reviewed them and tested them as described above.

[1] https://lore.kernel.org/all/20260505232244.71807-1-dalaport@amazon.com/

Sarah Maedel (2):
  i2c: designware: Only check for spurious STOP without
    EMPTYFIFO_HOLD_MASTER
  i2c: designware: Abort stuck master when disabling times out

 drivers/i2c/busses/i2c-designware-common.c | 19 +++++++++++++++++++
 drivers/i2c/busses/i2c-designware-master.c |  7 +++++--
 2 files changed, 24 insertions(+), 2 deletions(-)


base-commit: b3dfbde62cf1981c4638939c159dfd087b7a72e9
-- 
2.47.3