usb: xhci: Add debugfs support for xHCI Port Link Info (PORTLI) register.

Each xHCI roothub port has a Port Link Info (PORTLI) register that is
used by USB3 and eUSB2V2 ports.

USB3 ports show link error count, rx lane count, and tx lane count.

eUSB2V2 ports show Rx Data Rate (RDR) and Tx Data Rate (TDR).

Rx/Tx Data Rate is a multiple of USB2 2.0 HS 480 Mb/s data rates,
and is only valid if a eUSB2V2 device is connected (CCS=1).

0 = "USB 2.0 HS" normal HS 480 Mb/s, no eUSB2V2 in use
1 = "HS1" Assymetric eUSB2V2 where this direction runs normal 480Mb/s
2 = "HS2" 960Mb/s
...
10 = "HS10" 4.8 Gb/s, max eUSB2V2 rate

PORTLI is Reserved and preserve "RsvdP" for normal USB2 ports

Sample output of USB3 port PORTLI:
cat /sys/kernel/debug/usb/xhci/0000:00:14.0/ports/port14/portli
0x00000000 LEC=0 RLC=0 TLC=0

Signed-off-by: Rai, Amardeep <[e-mail]>
Co-developed-by: Mathias Nyman <[e-mail]>
Signed-off-by: Mathias Nyman <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/usb/host/xhci-caps.h

···
 /* bit 10 - Rsvd */
 /* bit 11 - HC support Double BW on a eUSB2 HS ISOC EP */
 #define HCC2_EUSB2_DIC		BIT(11)
-/* bits 31:12 - Rsvd */
+/* bit 12 - HC support eUSB2V2 capability */
+#define HCC2_E2V2C		BIT(12)
+/* bits 31:13 - Rsvd */

drivers/usb/host/xhci-debugfs.c

···
 	.release		= single_release,
 };
 
+static int xhci_portli_show(struct seq_file *s, void *unused)
+{
+	struct xhci_port	*port = s->private;
+	struct xhci_hcd		*xhci = hcd_to_xhci(port->rhub->hcd);
+	u32			portli;
+
+	portli = readl(&port->port_reg->portli);
+
+	/* PORTLI fields are valid if port is a USB3 or eUSB2V2 port */
+	if (port->rhub == &xhci->usb3_rhub)
+		seq_printf(s, "0x%08x LEC=%u RLC=%u TLC=%u\n", portli,
+			   PORT_LEC(portli), PORT_RX_LANES(portli), PORT_TX_LANES(portli));
+	else if (xhci->hcc_params2 & HCC2_E2V2C)
+		seq_printf(s, "0x%08x RDR=%u TDR=%u\n", portli,
+			   PORTLI_RDR(portli), PORTLI_TDR(portli));
+	else
+		seq_printf(s, "0x%08x RsvdP\n", portli);
+
+	return 0;
+}
+
+static int xhci_portli_open(struct inode *inode, struct file *file)
+{
+	return single_open(file, xhci_portli_show, inode->i_private);
+}
+
+static const struct file_operations portli_fops = {
+	.open			= xhci_portli_open,
+	.read			= seq_read,
+	.llseek			= seq_lseek,
+	.release		= single_release,
+};
+
 static void xhci_debugfs_create_files(struct xhci_hcd *xhci,
 				      struct xhci_file_map *files,
 				      size_t nentries, void *data,
···
 		dir = debugfs_create_dir(port_name, parent);
 		port = &xhci->hw_ports[i];
 		debugfs_create_file("portsc", 0644, dir, port, &port_fops);
+		debugfs_create_file("portli", 0444, dir, port, &portli_fops);
 	}
 }
 

drivers/usb/host/xhci-port.h

···
 #define PORT_TEST_MODE_SHIFT	28
 
 /* USB3 Protocol PORTLI  Port Link Information */
+#define PORT_LEC(p)		((p) & 0xffff)
 #define PORT_RX_LANES(p)	(((p) >> 16) & 0xf)
 #define PORT_TX_LANES(p)	(((p) >> 20) & 0xf)
+
+/* eUSB2v2 protocol PORTLI Port Link information, RsvdP for normal USB2 */
+#define PORTLI_RDR(p)		((p) & 0xf)
+#define PORTLI_TDR(p)		(((p) >> 4) & 0xf)
 
 /* USB2 Protocol PORTHLPMC */
 #define PORT_HIRDM(p)((p) & 3)