fpga: dfl: afu: add STP (SignalTap) support

STP (SignalTap) is one of the private features under the port for
debugging. This patch adds private feature driver support for it
to allow userspace applications to mmap related mmio region and
provide STP service.

Signed-off-by: Xu Yilun <[e-mail]>
Signed-off-by: Wu Hao <[e-mail]>
Acked-by: Moritz Fischer <[e-mail]>
Acked-by: Alan Tull <[e-mail]>
Signed-off-by: Moritz Fischer <[e-mail]>

drivers/fpga/dfl-afu-main.c

···
 	.init = port_afu_init,
 };
 
+static int port_stp_init(struct platform_device *pdev,
+			 struct dfl_feature *feature)
+{
+	struct resource *res = &pdev->resource[feature->resource_index];
+
+	return afu_mmio_region_add(dev_get_platdata(&pdev->dev),
+				   DFL_PORT_REGION_INDEX_STP,
+				   resource_size(res), res->start,
+				   DFL_PORT_REGION_MMAP | DFL_PORT_REGION_READ |
+				   DFL_PORT_REGION_WRITE);
+}
+
+static const struct dfl_feature_id port_stp_id_table[] = {
+	{.id = PORT_FEATURE_ID_STP,},
+	{0,}
+};
+
+static const struct dfl_feature_ops port_stp_ops = {
+	.init = port_stp_init,
+};
+
 static struct dfl_feature_driver port_feature_drvs[] = {
 	{
 		.id_table = port_hdr_id_table,
···
 	{
 		.id_table = port_err_id_table,
 		.ops = &port_err_ops,
+	},
+	{
+		.id_table = port_stp_id_table,
+		.ops = &port_stp_ops,
 	},
 	{
 		.ops = NULL,