Drivers need information about a channel prior to creating a channel
or they risk triggering message delivery on the remote side of a
connection.

Add PCC channel type to records and expose PCC channel type to client.

Signed-off-by: Adam Young <admiyo@os.amperecomputing.com>
---
 drivers/mailbox/pcc.c | 45 +++++++++++++++++++++++++++++++++++++++++++
 include/acpi/pcc.h    |  9 +++++++++
 2 files changed, 54 insertions(+)

diff --git a/drivers/mailbox/pcc.c b/drivers/mailbox/pcc.c
index b1c7d3e4c5e3..b9a01bfdc95d 100644
--- a/drivers/mailbox/pcc.c
+++ b/drivers/mailbox/pcc.c
@@ -349,6 +349,50 @@ static irqreturn_t pcc_mbox_irq(int irq, void *p)
 	return IRQ_HANDLED;
 }
 
+/**
+ * pcc_mbox_query_channel - returns information about the channel
+ *              without activating the channel.
+ *
+ * @q_chan: a pointer to an already allocated struct pcc_mbox_chan
+ *              that will be populated with the channel data.
+ * @subspace_id: The PCC Subspace index as parsed in the PCC client
+ *      ACPI package. This is used to lookup the array of PCC
+ *      subspaces as parsed by the PCC Mailbox controller.
+ *
+ * Return: 0 upon success or non-zero upon error.
+ */
+int
+pcc_mbox_query_channel(struct pcc_mbox_chan *q_chan, int subspace_id)
+{
+	struct pcc_mbox_chan *pcc_mchan;
+	struct pcc_chan_info *pchan;
+	struct mbox_chan *chan;
+
+	if (!q_chan)
+		return -EINVAL;
+
+	if (subspace_id < 0 || subspace_id >= pcc_chan_count)
+		return -ENOENT;
+	pchan = chan_info + subspace_id;
+	chan = pchan->chan.mchan;
+	if (IS_ERR(chan)) {
+		pr_err("Channel not found for idx: %d\n", subspace_id);
+		return -EBUSY;
+	}
+	pcc_mchan = &pchan->chan;
+
+	q_chan->shmem_base_addr = pcc_mchan->shmem_base_addr;
+	q_chan->shmem = NULL;
+	q_chan->shmem_size = pcc_mchan->shmem_size;
+	q_chan->latency = pcc_mchan->latency;
+	q_chan->max_access_rate = pcc_mchan->max_access_rate;
+	q_chan->min_turnaround_time = pcc_mchan->min_turnaround_time;
+	q_chan->type = pcc_mchan->type;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(pcc_mbox_query_channel);
+
 /**
  * pcc_mbox_request_channel - PCC clients call this function to
  *		request a pointer to their PCC subspace, from which they
@@ -833,6 +877,7 @@ static int pcc_mbox_probe(struct platform_device *pdev)
 		pcc_parse_subspace_shmem(pchan, pcct_entry);
 
 		pchan->type = pcct_entry->type;
+		pchan->chan.type = pcct_entry->type;
 		pcct_entry = (struct acpi_subtable_header *)
 			((unsigned long) pcct_entry + pcct_entry->length);
 	}
diff --git a/include/acpi/pcc.h b/include/acpi/pcc.h
index 840bfc95bae3..bf97f407683d 100644
--- a/include/acpi/pcc.h
+++ b/include/acpi/pcc.h
@@ -8,6 +8,7 @@
 
 #include <linux/mailbox_controller.h>
 #include <linux/mailbox_client.h>
+#include <linux/acpi.h>
 
 struct pcc_mbox_chan {
 	struct mbox_chan *mchan;
@@ -17,6 +18,7 @@ struct pcc_mbox_chan {
 	u32 latency;
 	u32 max_access_rate;
 	u16 min_turnaround_time;
+	enum acpi_pcct_type type;
 };
 
 /* Generic Communications Channel Shared Memory Region */
@@ -37,6 +39,8 @@ struct pcc_mbox_chan {
 extern struct pcc_mbox_chan *
 pcc_mbox_request_channel(struct mbox_client *cl, int subspace_id);
 extern void pcc_mbox_free_channel(struct pcc_mbox_chan *chan);
+extern int
+pcc_mbox_query_channel(struct pcc_mbox_chan *q_chan, int subspace_id);
 #else
 static inline struct pcc_mbox_chan *
 pcc_mbox_request_channel(struct mbox_client *cl, int subspace_id)
@@ -44,6 +48,11 @@ pcc_mbox_request_channel(struct mbox_client *cl, int subspace_id)
 	return ERR_PTR(-ENODEV);
 }
 static inline void pcc_mbox_free_channel(struct pcc_mbox_chan *chan) { }
+static inline int
+pcc_mbox_query_channel(struct pcc_mbox_chan *q_chan, int subspace_id)
+{
+	return -ENODEV;
+}
 #endif
 
 #endif /* _PCC_H */
-- 
2.43.0