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

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Message-Id: <20251016-pcc_mb_updates-v1-2-0fba69616f69@arm.com>
Date: Thu, 16 Oct 2025 20:08:16 +0100
From: Sudeep Holla <sudeep.holla@....com>
To: linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org
Cc: Sudeep Holla <sudeep.holla@....com>, 
 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: [PATCH 2/6] mailbox: pcc: Wire up ->last_tx_done() for PCC
 channels

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,
 };

 /**

-- 
2.34.1