usb: dwc3: add u2exit lfps quirk

This patch adds u2exit lfps quirk, and some special platforms can configure
that if it is needed.

[ balbi@ti.com : added DeviceTree binding documentation ]
Signed-off-by: Huang Rui <ray.huang@amd.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>

Documentation/devicetree/bindings/usb/dwc3.txt

@@ -18,6 +18,7 @@ Optional properties:
 	Only really useful for FPGA builds.
  - snps,has-lpm-erratum: true when DWC3 was configured with LPM Erratum enabled
  - snps,lpm-nyet-threshold: LPM NYET threshold
+ - snps,u2exit_lfps_quirk: set if we want to enable u2exit lfps quirk
 
 This is usually a subnode to DWC3 glue to which it is connected.
 

drivers/usb/dwc3/core.c

@@ -473,6 +473,9 @@ static int dwc3_core_init(struct dwc3 *dwc)
 	else
 		reg &= ~DWC3_GCTL_DISSCRAMBLE;
 
+	if (dwc->u2exit_lfps_quirk)
+		reg |= DWC3_GCTL_U2EXIT_LFPS;
+
 	/*
 	 * WORKAROUND: DWC3 revisions <1.90a have a bug
 	 * where the device can fail to connect at SuperSpeed
@@ -729,6 +732,8 @@ static int dwc3_probe(struct platform_device *pdev)
 
 		dwc->disable_scramble_quirk = of_property_read_bool(node,
 				"snps,disable_scramble_quirk");
+		dwc->u2exit_lfps_quirk = of_property_read_bool(node,
+				"snps,u2exit_lfps_quirk");
 	} else if (pdata) {
 		dwc->maximum_speed = pdata->maximum_speed;
 		dwc->has_lpm_erratum = pdata->has_lpm_erratum;
@@ -739,6 +744,7 @@ static int dwc3_probe(struct platform_device *pdev)
 		dwc->dr_mode = pdata->dr_mode;
 
 		dwc->disable_scramble_quirk = pdata->disable_scramble_quirk;
+		dwc->u2exit_lfps_quirk = pdata->u2exit_lfps_quirk;
 	}
 
 	/* default to superspeed if no maximum_speed passed */

drivers/usb/dwc3/core.h

@@ -166,6 +166,7 @@
 #define DWC3_GCTL_SCALEDOWN(n)		((n) << 4)
 #define DWC3_GCTL_SCALEDOWN_MASK	DWC3_GCTL_SCALEDOWN(3)
 #define DWC3_GCTL_DISSCRAMBLE		(1 << 3)
+#define DWC3_GCTL_U2EXIT_LFPS		(1 << 2)
 #define DWC3_GCTL_GBLHIBERNATIONEN	(1 << 1)
 #define DWC3_GCTL_DSBLCLKGTNG		(1 << 0)
 
@@ -679,6 +680,7 @@ struct dwc3_scratchpad_array {
  * @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
+ * @u2exit_lfps_quirk: set if we enable u2exit lfps quirk
  */
 struct dwc3 {
 	struct usb_ctrlrequest	*ctrl_req;
@@ -787,6 +789,7 @@ struct dwc3 {
 	unsigned		three_stage_setup:1;
 
 	unsigned		disable_scramble_quirk:1;
+	unsigned		u2exit_lfps_quirk:1;
 };
 
 /* -------------------------------------------------------------------------- */

drivers/usb/dwc3/platform_data.h

@@ -29,4 +29,5 @@ struct dwc3_platform_data {
 
 	unsigned disable_scramble_quirk:1;
 	unsigned has_lpm_erratum:1;
+	unsigned u2exit_lfps_quirk:1;
 };