From 0cd5afb0fdd40110f8c37acf28bceca80620317e Mon Sep 17 00:00:00 2001
From: Andrei-Liviu Simion <andrei.simion@xilinx.com>
Date: Thu, 30 Oct 2014 12:52:59 -0700
Subject: [PATCH] dptx: Improved remote DPCD reads/writes to automatically work
 on 16-byte chunks.

Some monitors don't support sideband messages with AUX reads greater than 16
bytes. This improvement breaks up the higher-level read/write request into
multiple reads/writes that work with up to 16 bytes in size.

These higher-level remote DPCD read/write functions also serve as a wrapper for
an AUX read/write in case that the link count total is equal to 1 (a read/write
request to the RX device directly connected to the TX (not "remote")).

Signed-off-by: Andrei-Liviu Simion <andrei.simion@xilinx.com>
---
 XilinxProcessorIPLib/drivers/dptx/src/xdptx.h |  7 ++
 .../drivers/dptx/src/xdptx_mst.c              | 78 +++++++++++++++++++
 2 files changed, 85 insertions(+)

diff --git a/XilinxProcessorIPLib/drivers/dptx/src/xdptx.h b/XilinxProcessorIPLib/drivers/dptx/src/xdptx.h
index eb263196..a0adb1e8 100644
--- a/XilinxProcessorIPLib/drivers/dptx/src/xdptx.h
+++ b/XilinxProcessorIPLib/drivers/dptx/src/xdptx.h
@@ -833,6 +833,13 @@ u32 XDptx_DiscoverTopology(XDptx *InstancePtr);
 u32 XDptx_FindAccessibleDpDevices(XDptx *InstancePtr, u8 LinkCountTotal,
 							u8 *RelativeAddress);
 
+/* xdptx_mst.c: Multi-stream transport (MST) functions for communicating
+ * with downstream DisplayPort devices. */
+u32 XDptx_RemoteDpcdRead(XDptx *InstancePtr, u8 LinkCountTotal,
+	u8 *RelativeAddress, u32 DpcdAddress, u32 BytesToRead, u8 *ReadData);
+u32 XDptx_RemoteDpcdWrite(XDptx *InstancePtr, u8 LinkCountTotal,
+	u8 *RelativeAddress, u32 DpcdAddress, u32 BytesToWrite, u8 *WriteData);
+
 /* xdptx_mst.c: Multi-stream transport (MST) functions related to MST stream
  * allocation. */
 u32 XDptx_AllocatePayloadStreams(XDptx *InstancePtr);
diff --git a/XilinxProcessorIPLib/drivers/dptx/src/xdptx_mst.c b/XilinxProcessorIPLib/drivers/dptx/src/xdptx_mst.c
index 3a522737..32dd8acb 100644
--- a/XilinxProcessorIPLib/drivers/dptx/src/xdptx_mst.c
+++ b/XilinxProcessorIPLib/drivers/dptx/src/xdptx_mst.c
@@ -706,6 +706,84 @@ u32 XDptx_FindAccessibleDpDevices(XDptx *InstancePtr, u8 LinkCountTotal,
 	return XST_SUCCESS;
 }
 
+u32 XDptx_RemoteDpcdRead(XDptx *InstancePtr, u8 LinkCountTotal,
+	u8 *RelativeAddress, u32 DpcdAddress, u32 BytesToRead, u8 *ReadData)
+{
+	u32 Status;
+
+	if (LinkCountTotal == 1) {
+		Status = XDptx_AuxRead(InstancePtr, DpcdAddress, BytesToRead,
+								ReadData);
+	}
+	else {
+		u32 BytesLeft = BytesToRead;
+		while (BytesLeft > 0) {
+			if (BytesLeft > 16) {
+				Status = XDptx_SendSbMsgRemoteDpcdRead(
+					InstancePtr, LinkCountTotal,
+					RelativeAddress, DpcdAddress, 16,
+					ReadData);
+				BytesLeft -= 16;
+				DpcdAddress += 16;
+				ReadData += 16;
+			}
+			else {
+				Status = XDptx_SendSbMsgRemoteDpcdRead(
+					InstancePtr, LinkCountTotal,
+					RelativeAddress, DpcdAddress, BytesLeft,
+					ReadData);
+				BytesLeft = 0;
+			}
+
+			if (Status != XST_SUCCESS) {
+				/* The AUX read transaction failed. */
+				return Status;
+			}
+		}
+	}
+
+	return Status;
+}
+
+u32 XDptx_RemoteDpcdWrite(XDptx *InstancePtr, u8 LinkCountTotal,
+	u8 *RelativeAddress, u32 DpcdAddress, u32 BytesToWrite, u8 *WriteData)
+{
+	u32 Status;
+
+	if (LinkCountTotal == 1) {
+		Status = XDptx_AuxWrite(InstancePtr, DpcdAddress, BytesToWrite,
+								WriteData);
+	}
+	else {
+		u32 BytesLeft = BytesToWrite;
+		while (BytesLeft > 0) {
+			if (BytesLeft > 16) {
+				Status = XDptx_SendSbMsgRemoteDpcdWrite(
+					InstancePtr, LinkCountTotal,
+					RelativeAddress, DpcdAddress, 16,
+					WriteData);
+				BytesLeft -= 16;
+				DpcdAddress += 16;
+				WriteData += 16;
+			}
+			else {
+				Status = XDptx_SendSbMsgRemoteDpcdWrite(
+					InstancePtr, LinkCountTotal,
+					RelativeAddress, DpcdAddress, BytesLeft,
+					WriteData);
+				BytesLeft = 0;
+			}
+
+			if (Status != XST_SUCCESS) {
+				/* The AUX read transaction failed. */
+				return Status;
+			}
+		}
+	}
+
+	return Status;
+}
+
 /******************************************************************************/
 /**
  * This function will allocate bandwidth for all enabled stream.