xhci: debugfs: add debugfs interface to enable compliance mode for a port

Enable compliance transition for a port by writing "compliance" to the
ports portsc file in debugfs.
port must be "Not-connected" and Link must be in RxDetect state to enable
compliance mode.

Only needed for host that have CTC flag set.
Allows state transitioning to compliance at 1st LFPS timeout.
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/host/xhci-debugfs.c

@@ -8,6 +8,7 @@
  */
 
 #include <linux/slab.h>
+#include <linux/uaccess.h>
 
 #include "xhci.h"
 #include "xhci-debugfs.h"
@@ -351,8 +352,44 @@ static int xhci_port_open(struct inode *inode, struct file *file)
 	return single_open(file, xhci_portsc_show, inode->i_private);
 }
 
+static ssize_t xhci_port_write(struct file *file,  const char __user *ubuf,
+			       size_t count, loff_t *ppos)
+{
+	struct seq_file         *s = file->private_data;
+	struct xhci_port	*port = s->private;
+	struct xhci_hcd		*xhci = hcd_to_xhci(port->rhub->hcd);
+	char                    buf[32];
+	u32			portsc;
+	unsigned long		flags;
+
+	if (copy_from_user(&buf, ubuf, min_t(size_t, sizeof(buf) - 1, count)))
+		return -EFAULT;
+
+	if (!strncmp(buf, "compliance", 10)) {
+		/* If CTC is clear, compliance is enabled by default */
+		if (!HCC2_CTC(xhci->hcc_params2))
+			return count;
+		spin_lock_irqsave(&xhci->lock, flags);
+		/* compliance mode can only be enabled on ports in RxDetect */
+		portsc = readl(port->addr);
+		if ((portsc & PORT_PLS_MASK) != XDEV_RXDETECT) {
+			spin_unlock_irqrestore(&xhci->lock, flags);
+			return -EPERM;
+		}
+		portsc = xhci_port_state_to_neutral(portsc);
+		portsc &= ~PORT_PLS_MASK;
+		portsc |= PORT_LINK_STROBE | XDEV_COMP_MODE;
+		writel(portsc, port->addr);
+		spin_unlock_irqrestore(&xhci->lock, flags);
+	} else {
+		return -EINVAL;
+	}
+	return count;
+}
+
 static const struct file_operations port_fops = {
 	.open			= xhci_port_open,
+	.write                  = xhci_port_write,
 	.read			= seq_read,
 	.llseek			= seq_lseek,
 	.release		= single_release,
@@ -491,7 +528,7 @@ static void xhci_debugfs_create_ports(struct xhci_hcd *xhci,
 			  num_ports + 1);
 		dir = debugfs_create_dir(port_name, parent);
 		port = &xhci->hw_ports[num_ports];
-		debugfs_create_file("portsc", 0444, dir, port, &port_fops);
+		debugfs_create_file("portsc", 0644, dir, port, &port_fops);
 	}
 }