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

["lihuisong (C)" <lihuisong@huawei.com>]

On 6/18/2026 8:06 PM, Sudeep Holla wrote:
> 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 ?
Hi Sudeep，

Review this logic again.
The mbox_bind_client is called on requesting PCC channel.
And mbox_bind_client could modify chan->txdone_method to 
MBOX_TXDONE_BY_ACK if client knows txdone and 'txdone_method' is 
MBOX_TXDONE_BY_POLL.
So I think your above commit is ok for these client drivers.

/Huisong