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

[Richard Fitzgerald]

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@xxxxxxxxxxxxxxxxxxxxx>
> > ---
> >   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);