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

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

On Thu, Jun 18, 2026 at 10:04:12AM +0800, lihuisong (C) wrote:
> Hi Sudeep,
> 
> On 6/13/2026 1:02 AM, 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>
> > Signed-off-by: Sudeep Holla <sudeep.holla@kernel.org>
> > ---
> >   drivers/mailbox/pcc.c | 7 ++++++-
> >   1 file changed, 6 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/mailbox/pcc.c b/drivers/mailbox/pcc.c
> > index 636879ae1db7..7c9451ab4527 100644
> > --- a/drivers/mailbox/pcc.c
> > +++ b/drivers/mailbox/pcc.c
> > @@ -447,9 +447,14 @@ static int pcc_send_data(struct mbox_chan *chan, void *data)
> >   static bool pcc_last_tx_done(struct mbox_chan *chan)
> >   {
> > +	bool ret;
> >   	struct pcc_chan_info *pchan = chan->con_priv;
> > -	return pcc_mbox_cmd_complete_check(pchan);
> > +	ret = pcc_mbox_cmd_complete_check(pchan);
> > +	if (ret && !pchan->plat_irq)
> > +		mbox_chan_received_data(chan, NULL);
> > +
> > +	return ret;
> >   }
> The mailbox_controller.h said that .last_tx_done() is used only if
> txdone_poll:=true && txdone_irq:=false.
> How about add a verification at the begining of this function? like "if
> (chan->txdone_method != MBOX_TXDONE_BY_POLL) return false;"
> And then call mbox_chan_received_data() directly if command completed.
> 

Thanks, it does makes sense to me. I will have look.

> This patch is ok to me if has above changes.
> Acked-by: lihuisong@huawei.com
> 
> 
> But pcc mbox controller can no longer work in MBOX_TXDONE_BY_ACK after your
> commit:
> 3349f800609e (mailbox: pcc: Set txdone_irq/txdone_poll based on PCCT flags).
> This may lead to above client drivers fail to send mailbox command, like
> cppc_acpi,hisi_uncore_freq and kunpeng_hccs.
> Because these client driver knows tx_done(knows_txdone: true), work on this
> mode and need to call mbox_client_txdone.
> Do you have some idea for this?

I wonder if we can ask the platform to avoid generating interrupts in those
case by setting/clearing "Notify on completion" in shmem. Do you think that
would work ?

-- 
Regards,
Sudeep