netdev - [PATCH v30 1/3] mailbox: pcc: Type3 Buffer handles ACK IRQ

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Message-ID: <20251016210225.612639-2-admiyo@os.amperecomputing.com>
Date: Thu, 16 Oct 2025 17:02:19 -0400
From: Adam Young <admiyo@...amperecomputing.com>
To: Sudeep Holla <sudeep.holla@....com>,
	Jassi Brar <jassisinghbrar@...il.com>
Cc: netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Jeremy Kerr <jk@...econstruct.com.au>,
	Matt Johnston <matt@...econstruct.com.au>,
	"David S . Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>,
	Jonathan Cameron <Jonathan.Cameron@...wei.com>,
	Huisong Li <lihuisong@...wei.com>
Subject: [PATCH  v30 1/3] mailbox: pcc: Type3 Buffer handles ACK IRQ

The PCC protocol type 3 requests include a field that indicates that the
recipient should trigger an interrupt once the message has been read
from the buffer. The sender uses this interrupt to know that a
transmission is complete, and it is safe to send additional messages.

Signed-off-by: Adam Young <admiyo@...amperecomputing.com>

mailbox/pcc extended memory helper functions
---
 drivers/mailbox/pcc.c | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/drivers/mailbox/pcc.c b/drivers/mailbox/pcc.c
index f6714c233f5a..978a7b674946 100644
--- a/drivers/mailbox/pcc.c
+++ b/drivers/mailbox/pcc.c
@@ -306,6 +306,18 @@ static void pcc_chan_acknowledge(struct pcc_chan_info *pchan)
 		pcc_chan_reg_read_modify_write(&pchan->db);
 }
 
+static bool pcc_last_tx_done(struct mbox_chan *chan)
+{
+	struct pcc_chan_info *pchan = chan->con_priv;
+	u64 val;
+
+	pcc_chan_reg_read(&pchan->cmd_complete, &val);
+	if (!val)
+		return false;
+	else
+		return true;
+}
+
 /**
  * pcc_mbox_irq - PCC mailbox interrupt handler
  * @irq:	interrupt number
@@ -340,6 +352,14 @@ static irqreturn_t pcc_mbox_irq(int irq, void *p)
 	 * required to avoid any possible race in updatation of this flag.
 	 */
 	pchan->chan_in_use = false;
+
+	/**
+	 * The remote side sent an ack.
+	 */
+	if (pchan->type == ACPI_PCCT_TYPE_EXT_PCC_MASTER_SUBSPACE &&
+	    chan->active_req)
+		mbox_chan_txdone(chan, 0);
+
 	mbox_chan_received_data(chan, NULL);
 
 	pcc_chan_acknowledge(pchan);
@@ -490,6 +510,7 @@ 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,
 };
 
 /**
-- 
2.43.0