fpga: dfl: afu: add header sub feature support

The port header register set is always present for port, it is mainly
for capability, control and status of the ports that AFU connected to.

This patch implements header sub feature support. Below user interfaces
are created by this patch.

Sysfs interface:
* /sys/class/fpga_region/<regionX>/<dfl-port.x>/id
  Read-only. Port ID.

Ioctl interface:
* DFL_FPGA_PORT_RESET
  Reset the FPGA Port and its AFU.
Signed-off-by: Tim Whisonant <tim.whisonant@intel.com>
Signed-off-by: Enno Luebbers <enno.luebbers@intel.com>
Signed-off-by: Shiva Rao <shiva.rao@intel.com>
Signed-off-by: Christopher Rauer <christopher.rauer@intel.com>
Signed-off-by: Xiao Guangrong <guangrong.xiao@linux.intel.com>
Signed-off-by: Wu Hao <hao.wu@intel.com>
Acked-by: Alan Tull <atull@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/ABI/testing/sysfs-platform-dfl-port

+What:		/sys/bus/platform/devices/dfl-port.0/id
+Date:		June 2018
+KernelVersion:	4.19
+Contact:	Wu Hao <hao.wu@intel.com>
+Description:	Read-only. It returns id of this port. One DFL FPGA device
+		may have more than one port. Userspace could use this id to
+		distinguish different ports under same FPGA device.

drivers/fpga/dfl-afu-main.c

@@ -16,6 +16,7 @@
 
 #include <linux/kernel.h>
 #include <linux/module.h>
+#include <linux/fpga-dfl.h>
 
 #include "dfl.h"
 
@@ -87,6 +88,41 @@ static int port_disable(struct platform_device *pdev)
 	return 0;
 }
 
+/*
+ * This function resets the FPGA Port and its accelerator (AFU) by function
+ * __port_disable and __port_enable (set port soft reset bit and then clear
+ * it). Userspace can do Port reset at any time, e.g. during DMA or Partial
+ * Reconfiguration. But it should never cause any system level issue, only
+ * functional failure (e.g. DMA or PR operation failure) and be recoverable
+ * from the failure.
+ *
+ * Note: the accelerator (AFU) is not accessible when its port is in reset
+ * (disabled). Any attempts on MMIO access to AFU while in reset, will
+ * result errors reported via port error reporting sub feature (if present).
+ */
+static int __port_reset(struct platform_device *pdev)
+{
+	int ret;
+
+	ret = port_disable(pdev);
+	if (!ret)
+		port_enable(pdev);
+
+	return ret;
+}
+
+static int port_reset(struct platform_device *pdev)
+{
+	struct dfl_feature_platform_data *pdata = dev_get_platdata(&pdev->dev);
+	int ret;
+
+	mutex_lock(&pdata->lock);
+	ret = __port_reset(pdev);
+	mutex_unlock(&pdata->lock);
+
+	return ret;
+}
+
 static int port_get_id(struct platform_device *pdev)
 {
 	void __iomem *base;
@@ -96,23 +132,63 @@ static int port_get_id(struct platform_device *pdev)
 	return FIELD_GET(PORT_CAP_PORT_NUM, readq(base + PORT_HDR_CAP));
 }
 
+static ssize_t
+id_show(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	int id = port_get_id(to_platform_device(dev));
+
+	return scnprintf(buf, PAGE_SIZE, "%d\n", id);
+}
+static DEVICE_ATTR_RO(id);
+
+static const struct attribute *port_hdr_attrs[] = {
+	&dev_attr_id.attr,
+	NULL,
+};
+
 static int port_hdr_init(struct platform_device *pdev,
 			 struct dfl_feature *feature)
 {
 	dev_dbg(&pdev->dev, "PORT HDR Init.\n");
 
-	return 0;
+	port_reset(pdev);
+
+	return sysfs_create_files(&pdev->dev.kobj, port_hdr_attrs);
 }
 
 static void port_hdr_uinit(struct platform_device *pdev,
 			   struct dfl_feature *feature)
 {
 	dev_dbg(&pdev->dev, "PORT HDR UInit.\n");
+
+	sysfs_remove_files(&pdev->dev.kobj, port_hdr_attrs);
+}
+
+static long
+port_hdr_ioctl(struct platform_device *pdev, struct dfl_feature *feature,
+	       unsigned int cmd, unsigned long arg)
+{
+	long ret;
+
+	switch (cmd) {
+	case DFL_FPGA_PORT_RESET:
+		if (!arg)
+			ret = port_reset(pdev);
+		else
+			ret = -EINVAL;
+		break;
+	default:
+		dev_dbg(&pdev->dev, "%x cmd not handled", cmd);
+		ret = -ENODEV;
+	}
+
+	return ret;
 }
 
 static const struct dfl_feature_ops port_hdr_ops = {
 	.init = port_hdr_init,
 	.uinit = port_hdr_uinit,
+	.ioctl = port_hdr_ioctl,
 };
 
 static struct dfl_feature_driver port_feature_drvs[] = {
@@ -154,6 +230,7 @@ static int afu_release(struct inode *inode, struct file *filp)
 
 	pdata = dev_get_platdata(&pdev->dev);
 
+	port_reset(pdev);
 	dfl_feature_dev_use_end(pdata);
 
 	return 0;

include/uapi/linux/fpga-dfl.h

@@ -29,8 +29,11 @@
 #define DFL_FPGA_MAGIC 0xB6
 
 #define DFL_FPGA_BASE 0
+#define DFL_PORT_BASE 0x40
 #define DFL_FME_BASE 0x80
 
+/* Common IOCTLs for both FME and AFU file descriptor */
+
 /**
  * DFL_FPGA_GET_API_VERSION - _IO(DFL_FPGA_MAGIC, DFL_FPGA_BASE + 0)
  *
@@ -49,6 +52,20 @@
 
 #define DFL_FPGA_CHECK_EXTENSION	_IO(DFL_FPGA_MAGIC, DFL_FPGA_BASE + 1)
 
+/* IOCTLs for AFU file descriptor */
+
+/**
+ * DFL_FPGA_PORT_RESET - _IO(DFL_FPGA_MAGIC, DFL_PORT_BASE + 0)
+ *
+ * Reset the FPGA Port and its AFU. No parameters are supported.
+ * Userspace can do Port reset at any time, e.g. during DMA or PR. But
+ * it should never cause any system level issue, only functional failure
+ * (e.g. DMA or PR operation failure) and be recoverable from the failure.
+ * Return: 0 on success, -errno of failure
+ */
+
+#define DFL_FPGA_PORT_RESET		_IO(DFL_FPGA_MAGIC, DFL_PORT_BASE + 0)
+
 /* IOCTLs for FME file descriptor */
 
 /**