| Message ID | 20220914160248.1047627-1-rf@opensource.cirrus.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | soundwire: Fixes for spurious and missing UNATTACH | expand |
On 14-09-22, 17:02, Richard Fitzgerald wrote: > The bus and cadence code has several bugs that cause UNATTACH notifications > to either be sent spuriously or to be missed. > > These can be seen occasionally with a single peripheral on the bus, but are > much more frequent with multiple peripherals, where several peripherals > could change state and report in consecutive PINGs. > > The root of all of these bugs seems to be a code design flaw that assumed > every PING status change would be handled separately. However, PINGs are > handled by a workqueue function and there is no guarantee when that function > will be scheduled to run or how much CPU time it will receive. PINGs will > continue while the work function is handling a snapshot of a previous PING > so the code must take account that (a) status could change during the > work function and (b) there can be a backlog of changes before the IRQ work > function runs again. Applied, thanks
The bus and cadence code has several bugs that cause UNATTACH notifications to either be sent spuriously or to be missed. These can be seen occasionally with a single peripheral on the bus, but are much more frequent with multiple peripherals, where several peripherals could change state and report in consecutive PINGs. The root of all of these bugs seems to be a code design flaw that assumed every PING status change would be handled separately. However, PINGs are handled by a workqueue function and there is no guarantee when that function will be scheduled to run or how much CPU time it will receive. PINGs will continue while the work function is handling a snapshot of a previous PING so the code must take account that (a) status could change during the work function and (b) there can be a backlog of changes before the IRQ work function runs again. Tested with 4 peripherals on 1 bus, and 8 peripherals on 2 buses. CHANGES SINCE V3: Fixed minor comment typo in patch #4. Richard Fitzgerald (4): soundwire: bus: Don't lose unattach notifications soundwire: bus: Don't re-enumerate before status is UNATTACHED soundwire: cadence: Fix lost ATTACHED interrupts when enumerating soundwire: bus: Don't exit early if no device IDs were programmed Simon Trimmer (1): soundwire: cadence: fix updating slave status when a bus has multiple peripherals drivers/soundwire/bus.c | 44 +++++++++++++--- drivers/soundwire/cadence_master.c | 80 ++++++++++++++++-------------- 2 files changed, 80 insertions(+), 44 deletions(-)