Signed-off-by: Adam Young <redacted>
---
  drivers/mailbox/pcc.c | 129 ++++++++++++++++++++++++++++++++++++++++++
  include/acpi/pcc.h    |  38 +++++++++++++
  2 files changed, 167 insertions(+)

diff --git a/drivers/mailbox/pcc.c b/drivers/mailbox/pcc.c
index 978a7b674946..653897d61db5 100644
--- a/drivers/mailbox/pcc.c
+++ b/drivers/mailbox/pcc.c

@@ -367,6 +367,46 @@ static irqreturn_t pcc_mbox_irq(int irq, void *p)
  	return IRQ_HANDLED;
  }
  
+static
+struct pcc_chan_info *lookup_channel_info(int subspace_id)
+{
+	struct pcc_chan_info *pchan;
+	struct mbox_chan *chan;
+
+	if (subspace_id < 0 || subspace_id >= pcc_chan_count)
+		return ERR_PTR(-ENOENT);
+
+	pchan = chan_info + subspace_id;
+	chan = pchan->chan.mchan;
+	if (IS_ERR(chan) || chan->cl) {
+		pr_err("Channel not found for idx: %d\n", subspace_id);
+		return ERR_PTR(-EBUSY);
+	}
+	return pchan;
+}
+
+/**
+ * pcc_mbox_buffer_size - PCC clients call this function to
+ *		request the size of the shared buffer in cases
+ *              where requesting the channel would prematurely
+ *              trigger channel activation and message delivery.
+ * @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: The size of the shared buffer.
+ */
+int pcc_mbox_buffer_size(int index)

+{
+	struct pcc_chan_info *pchan = lookup_channel_info(index);
+
+	if (IS_ERR(pchan))
+		return -1;
+	return pchan->chan.shmem_size;
+}
+EXPORT_SYMBOL_GPL(pcc_mbox_buffer_size);
+
+
  /**
   * pcc_mbox_request_channel - PCC clients call this function to
   *		request a pointer to their PCC subspace, from which they

@@ -437,6 +477,95 @@ void pcc_mbox_free_channel(struct pcc_mbox_chan *pchan)
  }
  EXPORT_SYMBOL_GPL(pcc_mbox_free_channel);
  
+/**
+ * pcc_mbox_query_bytes_available
+ *
+ * @pchan pointer to channel associated with buffer
+ * Return: the number of bytes available to read from the shared buffer
+ */
+int pcc_mbox_query_bytes_available(struct pcc_mbox_chan *pchan)
+{
+	struct pcc_extended_header pcc_header;
+	struct pcc_chan_info *pinfo = pchan->mchan->con_priv;
+	int data_len;
+	u64 val;
+
+	pcc_chan_reg_read(&pinfo->cmd_complete, &val);
+	if (val) {
+		pr_info("%s Buffer not enabled for reading", __func__);
+		return -1;
+	}
+	memcpy_fromio(&pcc_header, pchan->shmem,
+		      sizeof(pcc_header));
+	data_len = pcc_header.length - sizeof(u32) + sizeof(pcc_header);
+	return data_len;
+}
+EXPORT_SYMBOL_GPL(pcc_mbox_query_bytes_available);
+
+/**
+ * pcc_mbox_read_from_buffer - Copy bytes from shared buffer into data
+ *
+ * @pchan - channel associated with the shared buffer
+ * @len - number of bytes to read
+ * @data - pointer to memory in which to write the data from the
+ *         shared buffer
+ *
+ * Return: number of bytes read and written into daa

+ */
+int pcc_mbox_read_from_buffer(struct pcc_mbox_chan *pchan, int len, void *data)
+{
+	struct pcc_chan_info *pinfo = pchan->mchan->con_priv;
+	int data_len;
+	u64 val;
+
+	pcc_chan_reg_read(&pinfo->cmd_complete, &val);
+	if (val) {
+		pr_info("%s buffer not enabled for reading", __func__);
+		return -1;
+	}
+	data_len  = pcc_mbox_query_bytes_available(pchan);
+	if (len < data_len)
+		data_len = len;
+	memcpy_fromio(data, pchan->shmem, len);
+	return len;
+}
+EXPORT_SYMBOL_GPL(pcc_mbox_read_from_buffer);
+
+/**
+ * pcc_mbox_write_to_buffer, copy the contents of the data
+ * pointer to the shared buffer.  Confirms that the command
+ * flag has been set prior to writing.  Data should be a
+ * properly formatted extended data buffer.
+ * pcc_mbox_write_to_buffer
+ * @pchan: channel
+ * @len: Length of the overall buffer passed in, including the
+ *       Entire header. The length value in the shared buffer header
+ *       Will be calculated from len.
+ * @data: Client specific data to be written to the shared buffer.
+ * Return: number of bytes written to the buffer.
+ */
+int pcc_mbox_write_to_buffer(struct pcc_mbox_chan *pchan, int len, void *data)
+{
+	struct pcc_extended_header *pcc_header = data;
+	struct mbox_chan *mbox_chan = pchan->mchan;
+
+	/*
+	 * The PCC header length includes the command field
+	 * but not the other values from the header.
+	 */
+	pcc_header->length = len - sizeof(struct pcc_extended_header) + sizeof(u32);
+
+	if (!pcc_last_tx_done(mbox_chan)) {
+		pr_info("%s pchan->cmd_complete not set.", __func__);
+		return 0;
+	}
+	memcpy_toio(pchan->shmem,  data, len);
+
+	return len;
+}
+EXPORT_SYMBOL_GPL(pcc_mbox_write_to_buffer);
+
+
  /**
   * 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 840bfc95bae3..96a6f85fc1ba 100644
--- a/include/acpi/pcc.h
+++ b/include/acpi/pcc.h

@@ -19,6 +19,13 @@ struct pcc_mbox_chan {
  	u16 min_turnaround_time;
  };
  
+struct pcc_extended_header {
+	u32 signature;
+	u32 flags;
+	u32 length;
+	u32 command;
+};
+
  /* Generic Communications Channel Shared Memory Region */
  #define PCC_SIGNATURE			0x50434300
  /* Generic Communications Channel Command Field */

@@ -37,6 +44,17 @@ 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_write_to_buffer(struct pcc_mbox_chan *pchan, int len, void *data);
+extern
+int pcc_mbox_query_bytes_available(struct pcc_mbox_chan *pchan);
+extern
+int pcc_mbox_read_from_buffer(struct pcc_mbox_chan *pchan, int len,
+			      void *data);
+extern
+int pcc_mbox_buffer_size(int index);
+
+
  #else
  static inline struct pcc_mbox_chan *
  pcc_mbox_request_channel(struct mbox_client *cl, int subspace_id)

@@ -44,6 +62,26 @@ 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_write_to_buffer(struct pcc_mbox_chan *pchan, int len, void *data)
+{
+	return 0;
+}
+static inline int pcc_mbox_query_bytes_available(struct pcc_mbox_chan *pchan);