dptx: MST: Added check for MST capabilities before enabling.

Signed-off-by: Andrei-Liviu Simion <andrei.simion@xilinx.com>

XilinxProcessorIPLib/drivers/dptx/examples/xdptx_mst_example.c

@@ -170,6 +170,19 @@ u32 Dptx_MstExample(XDptx *InstancePtr, u16 DeviceId)
 		return XST_FAILURE;
 	}
 
+	Status = XDptx_MstCapable(InstancePtr);
+	if (Status != XST_SUCCESS) {
+		xil_printf("The immediate downstream DisplayPort device does "
+						"not have MST capabilities.\n");
+		/* If the immediate downstream RX device is an MST monitor and
+		 * the DisplayPort Configuration Data (DPCD) does not indicate
+		 * MST capability, it is likely that the MST or DisplayPort v1.2
+		 * option must be selected from the monitor's option menu. */
+		xil_printf("Check that the RX device is operating with a "
+			"DisplayPort version greater or equal to 1.2.\n");
+		return XST_FAILURE;
+	}
+
 	/* A DisplayPort connection must exist at this point. See the interrupt
 	 * and polling examples for waiting for connection events. */
 	Status = Dptx_StartLink(InstancePtr);

XilinxProcessorIPLib/drivers/dptx/src/xdptx.h

@@ -760,6 +760,7 @@ XDptx_Config *XDptx_LookupConfig(u16 DeviceId);
  * MST mode. */
 void XDptx_MstCfgModeEnable(XDptx *InstancePtr);
 void XDptx_MstCfgModeDisable(XDptx *InstancePtr);
+u32 XDptx_MstCapable(XDptx *InstancePtr);
 u32 XDptx_MstEnable(XDptx *InstancePtr);
 u32 XDptx_MstDisable(XDptx *InstancePtr);
 

XilinxProcessorIPLib/drivers/dptx/src/xdptx_hw.h

@@ -854,7 +854,7 @@
 #define XDPTX_DPCD_FAUX_FORWARD_CH_STATUS		0x00280
 #define XDPTX_DPCD_FAUX_BACK_CH_DRIVE_SET		0x00281
 #define XDPTX_DPCD_FAUX_BACK_CH_SYM_ERR_COUNT_CTRL	0x00282
-#define XDPTX_DPCD_PAYLOAD_TABLE_UPDATE_STATUS	0x002C0
+#define XDPTX_DPCD_PAYLOAD_TABLE_UPDATE_STATUS		0x002C0
 #define XDPTX_DPCD_VC_PAYLOAD_ID_SLOT(SlotNum) \
 			(XDPTX_DPCD_PAYLOAD_TABLE_UPDATE_STATUS + SlotNum)
 /* @} */

XilinxProcessorIPLib/drivers/dptx/src/xdptx_mst.c

@@ -226,6 +226,60 @@ void XDptx_MstCfgModeDisable(XDptx *InstancePtr)
 	InstancePtr->MstEnable = 0;
 }
 
+/******************************************************************************/
+/**
+ * This function will check if the immediate downstream RX device is capable of
+ * multi-stream transport (MST) mode. A DisplayPort Configuration Data (DPCD)
+ * version of 1.2 or higher is required and the MST capability bit in the DPCD
+ * must be set for this function to return XST_SUCCESS.
+ *
+ * @param	InstancePtr is a pointer to the XDptx instance.
+ *
+ * @return
+ *		- XST_SUCCESS if the RX device is MST capable.
+ *		- XST_NO_FEATURE if the RX device does not support MST.
+ *              - XST_DEVICE_NOT_FOUND if no RX device is connected.
+ *		- XST_ERROR_COUNT_MAX if an AUX read request timed out.
+ *		- XST_FAILURE otherwise - if an AUX read transaction failed.
+ *
+ * @note	None.
+ *
+*******************************************************************************/
+u32 XDptx_MstCapable(XDptx *InstancePtr)
+{
+	u32 Status;
+	u8 AuxData;
+
+	/* Verify arguments. */
+	Xil_AssertNonvoid(InstancePtr != NULL);
+	Xil_AssertNonvoid(InstancePtr->IsReady == XIL_COMPONENT_IS_READY);
+
+	/* Check that the RX device has a DisplayPort Configuration Data (DPCD)
+	 * version greater than or equal to 1.2 to be able to support MST
+	 * functionality. */
+	Status = XDptx_AuxRead(InstancePtr, XDPTX_DPCD_REV, 1, &AuxData);
+	if (Status != XST_SUCCESS) {
+		/* The AUX read transaction failed. */
+		return Status;
+	}
+	else if (AuxData < 0x12) {
+		return XST_NO_FEATURE;
+	}
+
+	/* Check if the RX device has MST capabilities.. */
+	Status = XDptx_AuxRead(InstancePtr, XDPTX_DPCD_MSTM_CAP, 1, &AuxData);
+	if (Status != XST_SUCCESS) {
+		/* The AUX read transaction failed. */
+		return Status;
+	}
+	else if ((AuxData & XDPTX_DPCD_MST_CAP_MASK) !=
+						XDPTX_DPCD_MST_CAP_MASK) {
+		return XST_NO_FEATURE;
+	}
+
+	return XST_SUCCESS;
+}
+
 /******************************************************************************/
 /**
  * This function will enable multi-stream transport (MST) mode in both the
@@ -236,6 +290,10 @@ void XDptx_MstCfgModeDisable(XDptx *InstancePtr)
  * @return
  *		- XST_SUCCESS if MST mode has been successful enabled in
  *		  hardware.
+ *		- XST_NO_FEATURE if the immediate downstream RX device does not
+ *		  support MST - that is, if its DisplayPort Configuration Data
+ *		  (DPCD) version is less than 1.2, or if the DPCD indicates that
+ *		  it has no DPCD capabilities.
  *              - XST_DEVICE_NOT_FOUND if no RX device is connected.
  *		- XST_ERROR_COUNT_MAX if an AUX request timed out.
  *		- XST_FAILURE otherwise - if an AUX read or write transaction
@@ -253,6 +311,13 @@ u32 XDptx_MstEnable(XDptx *InstancePtr)
 	Xil_AssertNonvoid(InstancePtr != NULL);
 	Xil_AssertNonvoid(InstancePtr->IsReady == XIL_COMPONENT_IS_READY);
 
+	/* Check if the immediate downstream RX device has MST capabilities. */
+	Status = XDptx_MstCapable(InstancePtr);
+	if (Status != XST_SUCCESS) {
+		/* The RX device is not downstream capable. */
+		return Status;
+	}
+
 	/* HPD long pulse used for upstream notification. */
 	AuxData = 0;
 	Status = XDptx_AuxWrite(InstancePtr, XDPTX_DPCD_BRANCH_DEVICE_CTRL, 1,
@@ -276,6 +341,7 @@ u32 XDptx_MstEnable(XDptx *InstancePtr)
 	XDptx_WriteReg(InstancePtr->Config.BaseAddr, XDPTX_TX_MST_CONFIG,
 					XDPTX_TX_MST_CONFIG_MST_EN_MASK);
 
+	XDptx_MstCfgModeEnable(InstancePtr);
 	return XST_SUCCESS;
 }
 
@@ -316,6 +382,7 @@ u32 XDptx_MstDisable(XDptx *InstancePtr)
 	/* Disable MST mode in the DisplayPort TX. */
 	XDptx_WriteReg(InstancePtr->Config.BaseAddr, XDPTX_TX_MST_CONFIG, 0x0);
 
+	XDptx_MstCfgModeDisable(InstancePtr);
 	return XST_SUCCESS;
 }