usb: dwc3: add disscramble quirk

This patch adds disscramble quirk, and it only needs to be enabled at fpga
board on some vendor platforms.

Signed-off-by: Huang Rui <ray.huang@amd.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>
diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
index 9830f87..a0ae132 100644
--- a/drivers/usb/dwc3/core.c
+++ b/drivers/usb/dwc3/core.c
@@ -422,7 +422,6 @@
 
 	reg = dwc3_readl(dwc->regs, DWC3_GCTL);
 	reg &= ~DWC3_GCTL_SCALEDOWN_MASK;
-	reg &= ~DWC3_GCTL_DISSCRAMBLE;
 
 	switch (DWC3_GHWPARAMS1_EN_PWROPT(dwc->hwparams.hwparams1)) {
 	case DWC3_GHWPARAMS1_EN_PWROPT_CLK:
@@ -466,6 +465,14 @@
 		dwc->is_fpga = true;
 	}
 
+	WARN_ONCE(dwc->disable_scramble_quirk && !dwc->is_fpga,
+			"disable_scramble cannot be used on non-FPGA builds\n");
+
+	if (dwc->disable_scramble_quirk && dwc->is_fpga)
+		reg |= DWC3_GCTL_DISSCRAMBLE;
+	else
+		reg &= ~DWC3_GCTL_DISSCRAMBLE;
+
 	/*
 	 * WORKAROUND: DWC3 revisions <1.90a have a bug
 	 * where the device can fail to connect at SuperSpeed
@@ -710,11 +717,16 @@
 
 		dwc->needs_fifo_resize = of_property_read_bool(node, "tx-fifo-resize");
 		dwc->dr_mode = of_usb_get_dr_mode(node);
+
+		dwc->disable_scramble_quirk = of_property_read_bool(node,
+				"snps,disable_scramble_quirk");
 	} else if (pdata) {
 		dwc->maximum_speed = pdata->maximum_speed;
 
 		dwc->needs_fifo_resize = pdata->tx_fifo_resize;
 		dwc->dr_mode = pdata->dr_mode;
+
+		dwc->disable_scramble_quirk = pdata->disable_scramble_quirk;
 	}
 
 	/* default to superspeed if no maximum_speed passed */