linux-kernel - Re: [PATCH 2/6] mailbox: pcc: Wire up ->last_tx

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Message-ID: <81929a1d-6730-4ae3-9c91-c4cbfba44a7c@amperemail.onmicrosoft.com>
Date: Fri, 17 Oct 2025 12:48:33 -0400
From: Adam Young <admiyo@...eremail.onmicrosoft.com>
To: Sudeep Holla <sudeep.holla@....com>, linux-acpi@...r.kernel.org,
 linux-kernel@...r.kernel.org
Cc: Adam Young <admiyo@...amperecomputing.com>,
 Robbie King <robbiek@...ghtlabs.com>, Huisong Li <lihuisong@...wei.com>,
 Jassi Brar <jassisinghbrar@...il.com>,
 Cristian Marussi <cristian.marussi@....com>
Subject: Re: [PATCH 2/6] mailbox: pcc: Wire up ->last_tx_done() for PCC
 channels

Tested-by: Adam Young <admiyo@...amperecompuing.com>

On 10/16/25 15:08, Sudeep Holla wrote:
> Some PCC users poll for completion between transfers and benefit from
> the knowledge of previous Tx completion check through the mailbox
> framework's ->last_tx_done() op.
>
> Hook up the last_tx_done callback in the PCC mailbox driver so the mailbox
> framework can correctly query the completion status of the last transmitted
> message. This aligns PCC with other controllers that already implement such
> last_tx_done status query.
>
> No functional change unless callers use ->last_tx_done(). Normal Tx and
> IRQ paths are unchanged. This change just improves synchronization and
> avoids unnecessary timeouts for non-interrupt driven channels by ensuring
> correct completion detection for PCC channels that don’t rely on interrupts.
>
> Signed-off-by: Sudeep Holla <sudeep.holla@....com>
> ---
>   drivers/mailbox/pcc.c | 8 ++++++++
>   1 file changed, 8 insertions(+)
>
> diff --git a/drivers/mailbox/pcc.c b/drivers/mailbox/pcc.c
> index f6714c233f5a..2b690c268cf0 100644
> --- a/drivers/mailbox/pcc.c
> +++ b/drivers/mailbox/pcc.c
> @@ -445,6 +445,13 @@ static int pcc_send_data(struct mbox_chan *chan, void *data)
>   	return ret;
>   }
>   
> +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);
> +}
> +
>   /**
>    * pcc_startup - Called from Mailbox Controller code. Used here
>    *		to request the interrupt.
> @@ -490,6 +497,7 @@ static const struct mbox_chan_ops pcc_chan_ops = {
>   	.send_data = pcc_send_data,
>   	.startup = pcc_startup,
>   	.shutdown = pcc_shutdown,
> +	.last_tx_done = pcc_last_tx_done,
>   };
>   
>   /**
>