usb: dwc3: debugfs: Print/set link state for peripheral mode

Current implementation only prints/sets the link state for peripheral
mode only. Check and prevent printing bogus link state if the current
mode of operation is not peripheral.
Signed-off-by: Thinh Nguyen <thinhn@synopsys.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

drivers/usb/dwc3/debugfs.c

@@ -542,6 +542,13 @@ static int dwc3_link_state_show(struct seq_file *s, void *unused)
 	u8			speed;
 
 	spin_lock_irqsave(&dwc->lock, flags);
+	reg = dwc3_readl(dwc->regs, DWC3_GSTS);
+	if (DWC3_GSTS_CURMOD(reg) != DWC3_GSTS_CURMOD_DEVICE) {
+		seq_puts(s, "Not available\n");
+		spin_unlock_irqrestore(&dwc->lock, flags);
+		return 0;
+	}
+
 	reg = dwc3_readl(dwc->regs, DWC3_DSTS);
 	state = DWC3_DSTS_USBLNKST(reg);
 	speed = reg & DWC3_DSTS_CONNECTSPD;
@@ -589,6 +596,12 @@ static ssize_t dwc3_link_state_write(struct file *file,
 		return -EINVAL;
 
 	spin_lock_irqsave(&dwc->lock, flags);
+	reg = dwc3_readl(dwc->regs, DWC3_GSTS);
+	if (DWC3_GSTS_CURMOD(reg) != DWC3_GSTS_CURMOD_DEVICE) {
+		spin_unlock_irqrestore(&dwc->lock, flags);
+		return -EINVAL;
+	}
+
 	reg = dwc3_readl(dwc->regs, DWC3_DSTS);
 	speed = reg & DWC3_DSTS_CONNECTSPD;