Re: [PATCH 5/7] soundwire: intel: Don't disable interrupt until children are removed

Richard Fitzgerald
2022-09-12T15:36:48Z

On 12/09/2022 11:53, Pierre-Louis Bossart wrote:
>
>
> On 9/7/22 12:14, Richard Fitzgerald wrote:
>> The cadence_master code needs the interrupt to complete message transfers.
>> When the bus driver is being removed child drivers are removed, and their
>> remove actions might need bus transactions.
>>
>> Use the sdw_master_ops.remove callback to disable the interrupt handling
>> only after the child drivers have been removed.
>>
>> Signed-off-by: Richard Fitzgerald <rf@opensource.cirrus.com>
>> ---
>> drivers/soundwire/intel.c | 9 ++++++++-
>> 1 file changed, 8 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/soundwire/intel.c b/drivers/soundwire/intel.c
>> index 01be62fa6c83..d5e723a9c80b 100644
>> --- a/drivers/soundwire/intel.c
>> +++ b/drivers/soundwire/intel.c
>> @@ -1255,6 +1255,13 @@ static int intel_prop_read(struct sdw_bus *bus)
>> return 0;
>> }
>>
>> +static void intel_bus_remove(struct sdw_bus *bus)
>> +{
>> + struct sdw_cdns *cdns = bus_to_cdns(bus);
>> +
>> + sdw_cdns_enable_interrupt(cdns, false);
>
> don't you need to check for any on-going transactions on the bus?
>

As all the child drivers have removed, I think the only other place that
can generate bus transactions is the PING handler but
sdw_cdns_enable_interrupt(false) calls cancel_work_sync() to
cancel the cdns->work and it sets a flag so that it will not be
re-queued.

> I wonder if there could be a corner case where there are no child
> devices but still a device physically attached to the bus. I am not sure
> if the 'no devices left' is a good-enough indication of no activity on
> the bus.
>

As above - yes there could, but sdw_cdns_enable_interrupt(false) will
cancel the work and stop it being re-queued.

>> +}
>> +
>> static struct sdw_master_ops sdw_intel_ops = {
>> .read_prop = sdw_master_read_prop,
>> .override_adr = sdw_dmi_override_adr,
>> @@ -1264,6 +1271,7 @@ static struct sdw_master_ops sdw_intel_ops = {
>> .set_bus_conf = cdns_bus_conf,
>> .pre_bank_switch = intel_pre_bank_switch,
>> .post_bank_switch = intel_post_bank_switch,
>> + .remove = intel_bus_remove,
>> };
>>
>> static int intel_init(struct sdw_intel *sdw)
>> @@ -1502,7 +1510,6 @@ static void intel_link_remove(struct auxiliary_device *auxdev)
>> */
>> if (!bus->prop.hw_disabled) {
>> intel_debugfs_exit(sdw);
>> - sdw_cdns_enable_interrupt(cdns, false);
>> snd_soc_unregister_component(dev);
>> }
>> sdw_bus_master_delete(bus);