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

Adam Young
2025-10-16T21:02:38Z

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@os.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