diff --git a/drivers/mailbox/pcc.c b/drivers/mailbox/pcc.c
index 94885e411085ad..82102a4c5d6883 100644
--- a/drivers/mailbox/pcc.c
+++ b/drivers/mailbox/pcc.c
@@ -269,6 +269,35 @@ static bool pcc_mbox_cmd_complete_check(struct pcc_chan_info *pchan)
 	return !!val;
 }
 
+static void check_and_ack(struct pcc_chan_info *pchan, struct mbox_chan *chan)
+{
+	struct acpi_pcct_ext_pcc_shared_memory pcc_hdr;
+
+	if (pchan->type != ACPI_PCCT_TYPE_EXT_PCC_SLAVE_SUBSPACE)
+		return;
+	/* If the memory region has not been mapped, we cannot
+	 * determine if we need to send the message, but we still
+	 * need to set the cmd_update flag before returning.
+	 */
+	if (pchan->chan.shmem == NULL) {
+		pcc_chan_reg_read_modify_write(&pchan->cmd_update);
+		return;
+	}
+	memcpy_fromio(&pcc_hdr, pchan->chan.shmem,
+		      sizeof(struct acpi_pcct_ext_pcc_shared_memory));
+	/*
+	 * The PCC slave subspace channel needs to set the command complete bit
+	 * after processing message. If the PCC_ACK_FLAG is set, it should also
+	 * ring the doorbell.
+	 *
+	 * The PCC master subspace channel clears chan_in_use to free channel.
+	 */
+	if (le32_to_cpup(&pcc_hdr.flags) & PCC_ACK_FLAG_MASK)
+		pcc_send_data(chan, NULL);
+	else
+		pcc_chan_reg_read_modify_write(&pchan->cmd_update);
+}
+
 /**
  * pcc_mbox_irq - PCC mailbox interrupt handler
  * @irq:	interrupt number
@@ -306,14 +335,7 @@ static irqreturn_t pcc_mbox_irq(int irq, void *p)
 
 	mbox_chan_received_data(chan, NULL);
 
-	/*
-	 * The PCC slave subspace channel needs to set the command complete bit
-	 * and ring doorbell after processing message.
-	 *
-	 * The PCC master subspace channel clears chan_in_use to free channel.
-	 */
-	if (pchan->type == ACPI_PCCT_TYPE_EXT_PCC_SLAVE_SUBSPACE)
-		pcc_send_data(chan, NULL);
+	check_and_ack(pchan, chan);
 	pchan->chan_in_use = false;
 
 	return IRQ_HANDLED;
@@ -365,14 +387,37 @@ EXPORT_SYMBOL_GPL(pcc_mbox_request_channel);
 void pcc_mbox_free_channel(struct pcc_mbox_chan *pchan)
 {
 	struct mbox_chan *chan = pchan->mchan;
+	struct pcc_chan_info *pchan_info;
+	struct pcc_mbox_chan *pcc_mbox_chan;
 
 	if (!chan || !chan->cl)
 		return;
+	pchan_info = chan->con_priv;
+	pcc_mbox_chan = &pchan_info->chan;
+	if (pcc_mbox_chan->shmem) {
+		iounmap(pcc_mbox_chan->shmem);
+		pcc_mbox_chan->shmem = NULL;
+	}
 
 	mbox_free_channel(chan);
 }
 EXPORT_SYMBOL_GPL(pcc_mbox_free_channel);
 
+int pcc_mbox_ioremap(struct mbox_chan *chan)
+{
+	struct pcc_chan_info *pchan_info;
+	struct pcc_mbox_chan *pcc_mbox_chan;
+
+	if (!chan || !chan->cl)
+		return -1;
+	pchan_info = chan->con_priv;
+	pcc_mbox_chan = &pchan_info->chan;
+	pcc_mbox_chan->shmem = ioremap(pcc_mbox_chan->shmem_base_addr,
+				       pcc_mbox_chan->shmem_size);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(pcc_mbox_ioremap);
+
 /**
  * pcc_send_data - Called from Mailbox Controller code. Used
  *		here only to ring the channel doorbell. The PCC client
diff --git a/include/acpi/pcc.h b/include/acpi/pcc.h
index 9b373d172a7760..699c1a37b8e784 100644
--- a/include/acpi/pcc.h
+++ b/include/acpi/pcc.h
@@ -12,6 +12,7 @@
 struct pcc_mbox_chan {
 	struct mbox_chan *mchan;
 	u64 shmem_base_addr;
+	void __iomem *shmem;
 	u64 shmem_size;
 	u32 latency;
 	u32 max_access_rate;
@@ -31,11 +32,13 @@ struct pcc_mbox_chan {
 #define PCC_CMD_COMPLETION_NOTIFY	BIT(0)
 
 #define MAX_PCC_SUBSPACES	256
+#define PCC_ACK_FLAG_MASK	0x1
 
 #ifdef CONFIG_PCC
 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_ioremap(struct mbox_chan *chan);
 #else
 static inline struct pcc_mbox_chan *
 pcc_mbox_request_channel(struct mbox_client *cl, int subspace_id)
@@ -43,6 +46,10 @@ 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_ioremap(struct mbox_chan *chan)
+{
+	return 0;
+};
 #endif
 
 #endif /* _PCC_H */