linux-kernel - [PATCH net-next v29 2/3] mailbox/pcc: use mailbox-api level rx

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Message-ID: <20250925190027.147405-3-admiyo@os.amperecomputing.com>
Date: Thu, 25 Sep 2025 15:00:25 -0400
From: Adam Young <admiyo@...amperecomputing.com>
To: Sudeep Holla <sudeep.holla@....com>,
	Jassi Brar <jassisinghbrar@...il.com>,
	"Rafael J. Wysocki" <rafael@...nel.org>,
	Robert Moore <robert.moore@...el.com>,
	Len Brown <lenb@...nel.org>
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 net-next v29 2/3] mailbox/pcc: use mailbox-api level rx_alloc callback

Uses the newly introduced mailbox_api rx_alloc callback. Since this
callback is registered in the call to request a channel, it prevents a
race condition.  Without it, it is impossible to assign the callback before
activating the mailbox delivery of messages.

This patch also removes the flag pcc_mchan->manage_writes which
is not necessary: only type 3 and type 4 subspaces will have their
buffers managed by the mailbox.  It is not required for the driver
to explicitly specify.  If a future type 3 or type 4 drivers wishes
to manage the buffer directly, they can do so by passing NULL in
to mbox_send_message.

Signed-off-by: Adam Young <admiyo@...amperecomputing.com>
---
 drivers/mailbox/pcc.c | 16 ++++++++++------
 include/acpi/pcc.h    | 22 ----------------------
 2 files changed, 10 insertions(+), 28 deletions(-)

diff --git a/drivers/mailbox/pcc.c b/drivers/mailbox/pcc.c
index 0a00719b2482..4535cd208b9e 100644
--- a/drivers/mailbox/pcc.c
+++ b/drivers/mailbox/pcc.c
@@ -309,17 +309,20 @@ static void pcc_chan_acknowledge(struct pcc_chan_info *pchan)
 static void *write_response(struct pcc_chan_info *pchan)
 {
 	struct pcc_header pcc_header;
+	struct mbox_client *cl;
+	void *handle;
 	void *buffer;
 	int data_len;
 
+	cl = pchan->chan.mchan->cl;
 	memcpy_fromio(&pcc_header, pchan->chan.shmem,
 		      sizeof(pcc_header));
 	data_len = pcc_header.length - sizeof(u32) + sizeof(struct pcc_header);
 
-	buffer = pchan->chan.rx_alloc(pchan->chan.mchan->cl, data_len);
+	cl->rx_alloc(cl, &handle, &buffer, data_len);
 	if (buffer != NULL)
 		memcpy_fromio(buffer, pchan->chan.shmem, data_len);
-	return buffer;
+	return handle;
 }
 
 /**
@@ -359,7 +362,7 @@ static irqreturn_t pcc_mbox_irq(int irq, void *p)
 	 */
 	pchan->chan_in_use = false;
 
-	if (pchan->chan.rx_alloc)
+	if (pchan->chan.mchan->cl->rx_alloc)
 		handle = write_response(pchan);
 
 	if (chan->active_req) {
@@ -415,8 +418,6 @@ pcc_mbox_request_channel(struct mbox_client *cl, int subspace_id)
 	if (!pcc_mchan->shmem)
 		goto err;
 
-	pcc_mchan->manage_writes = false;
-
 	/* This indicates that the channel is ready to accept messages.
 	 * This needs to happen after the channel has registered
 	 * its callback. There is no access point to do that in
@@ -466,7 +467,10 @@ static int pcc_write_to_buffer(struct mbox_chan *chan, void *data)
 	struct pcc_mbox_chan *pcc_mbox_chan = &pchan->chan;
 	struct pcc_header *pcc_header = data;
 
-	if (!pchan->chan.manage_writes)
+	if (data == NULL)
+		return 0;
+	if (pchan->type < ACPI_PCCT_TYPE_EXT_PCC_MASTER_SUBSPACE ||
+	    pchan->type > ACPI_PCCT_TYPE_EXT_PCC_SLAVE_SUBSPACE)
 		return 0;
 
 	/* The PCC header length includes the command field
diff --git a/include/acpi/pcc.h b/include/acpi/pcc.h
index 9af3b502f839..5506490e628c 100644
--- a/include/acpi/pcc.h
+++ b/include/acpi/pcc.h
@@ -17,28 +17,6 @@ struct pcc_mbox_chan {
 	u32 latency;
 	u32 max_access_rate;
 	u16 min_turnaround_time;
-
-	/* Set to true to indicate that the mailbox should manage
-	 * writing the dat to the shared buffer. This differs from
-	 * the case where the drivesr are writing to the buffer and
-	 * using send_data only to  ring the doorbell.  If this flag
-	 * is set, then the void * data parameter of send_data must
-	 * point to a kernel-memory buffer formatted in accordance with
-	 * the PCC specification.
-	 *
-	 * The active buffer management will include reading the
-	 * notify_on_completion flag, and will then
-	 * call mbox_chan_txdone when the acknowledgment interrupt is
-	 * received.
-	 */
-	bool manage_writes;
-
-	/* Optional callback that allows the driver
-	 * to allocate the memory used for receiving
-	 * messages.  The return value is the location
-	 * inside the buffer where the mailbox should write the data.
-	 */
-	void *(*rx_alloc)(struct mbox_client *cl,  int size);
 };
 
 struct pcc_header {
-- 
2.43.0