Re: [PATCH 1/3] mailbox: pcc: Notify clients on polled completion

[Sudeep Holla <sudeep.holla@kernel.org>]

On Fri, Jul 24, 2026 at 01:11:06PM -0400, Adam Young wrote:
> 
> On 7/23/26 15:45, Sudeep Holla wrote:
> > On Thu, Jul 23, 2026 at 12:03:45PM -0400, Adam Young wrote:
> > > On 7/17/26 03:56, Sudeep Holla wrote:
> > > > PCC channels without a platform interrupt rely on the mailbox
> > > > polling path to detect command completion.
> > > > 
> > > > That path currently only reports transmit completion to the mailbox
> > > > core, so clients that wait for their receive callback do not get
> > > > notified when the command completes.
> > > > 
> > > > Call mbox_chan_received_data() when polling observes completion on a
> > > > channel without a platform IRQ, matching the interrupt-driven
> > > > completion path.
> > > > 
> > > > Reported-by: Cristian Marussi <cristian.marussi@arm.com>
> > > > Acked-by: Huisong Li <lihuisong@huawei.com>
> > > > Signed-off-by: Sudeep Holla <sudeep.holla@kernel.org>
> > > > ---
> > > >    drivers/mailbox/pcc.c | 10 +++++++++-
> > > >    1 file changed, 9 insertions(+), 1 deletion(-)
> > > > 
> > > > diff --git a/drivers/mailbox/pcc.c b/drivers/mailbox/pcc.c
> > > > index 636879ae1db7..d96b8b54e77e 100644
> > > > --- a/drivers/mailbox/pcc.c
> > > > +++ b/drivers/mailbox/pcc.c
> > > > @@ -449,7 +449,15 @@ static bool pcc_last_tx_done(struct mbox_chan *chan)
> > > >    {
> > > >    	struct pcc_chan_info *pchan = chan->con_priv;
> > > > -	return pcc_mbox_cmd_complete_check(pchan);
> > > > +	if (!(chan->txdone_method & MBOX_TXDONE_BY_POLL))
> > > > +		return false;
> > > > +
> > > > +	if (!pcc_mbox_cmd_complete_check(pchan))
> > > > +		return false;
> > > > +
> > > > +	mbox_chan_received_data(chan, NULL);
> > > > +
> > > > +	return true;
> > > >    }
> > > >    /**
> > > My code doesn't poll, so I cannot really claim to have tested it, but it
> > > does not break the existing IRQ based driver mechanism.
> > > 
> > Thanks for testing IRQ mode.
> > 
> > > I can claim to have read through the code and confirm that it is comparable
> > > to what happens on the IRQ case:   It clears the cmd_complete field and
> > > calls mbox_chan_received_data.
> > Thanks for taking a look and reviewing it.
> > 
> > > However, it does not clear pchan->chan_in_use
> > > = false; (Which should now be a WRITE_ONCE) and I would like to confirm that
> > > is not an oversight before providing a reviewed-by tag.
> > > 
> > IIRC I think we set the flag only when irq > 0, no ?
> 
> That is right.  So, this code is good.
> 
> Reviewed-by: Adam Young <admiyo@os.amperecomputing.com>

I have posted v2 [1] with the fix in 3/3, so please add any tags there so
that Jassi can pick it up easily.

-- 
Regards,
Sudeep

[1] https://lore.kernel.org/linux-acpi/20260723143928.2625970-1-sudeep.holla@kernel.org