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>

Documentation/devicetree/bindings/usb/dwc3.txt

@@ -14,6 +14,8 @@ Optional properties:
  - phys: from the *Generic PHY* bindings
  - phy-names: from the *Generic PHY* bindings
  - tx-fifo-resize: determines if the FIFO *has* to be reallocated.
+ - snps,disable_scramble_quirk: true when SW should disable data scrambling.
+	Only really useful for FPGA builds.
 
 This is usually a subnode to DWC3 glue to which it is connected.
 

drivers/usb/dwc3/core.c

@@ -422,7 +422,6 @@ static int dwc3_core_init(struct dwc3 *dwc)
 
 	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 @@ static int dwc3_core_init(struct dwc3 *dwc)
 		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 @@ static int dwc3_probe(struct platform_device *pdev)
 
 		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 */

drivers/usb/dwc3/core.h

@@ -672,6 +672,7 @@ struct dwc3_scratchpad_array {
  * @setup_packet_pending: true when there's a Setup Packet in FIFO. Workaround
  * @start_config_issued: true when StartConfig command has been issued
  * @three_stage_setup: set if we perform a three phase setup
+ * @disable_scramble_quirk: set if we enable the disable scramble quirk
  */
 struct dwc3 {
 	struct usb_ctrlrequest	*ctrl_req;
@@ -776,6 +777,8 @@ struct dwc3 {
 	unsigned		setup_packet_pending:1;
 	unsigned		start_config_issued:1;
 	unsigned		three_stage_setup:1;
+
+	unsigned		disable_scramble_quirk:1;
 };
 
 /* -------------------------------------------------------------------------- */

drivers/usb/dwc3/platform_data.h

@@ -24,4 +24,6 @@ struct dwc3_platform_data {
 	enum usb_device_speed maximum_speed;
 	enum usb_dr_mode dr_mode;
 	bool tx_fifo_resize;
+
+	unsigned disable_scramble_quirk:1;
 };