usb: dwc3: add Tx de-emphasis quirk

This patch adds Tx de-emphasis quirk, and the Tx de-emphasis value is
configurable according to PIPE3 specification.

Value		Description
0		-6dB de-emphasis
1		-3.5dB de-emphasis
2		No de-emphasis
3		Reserved

It can be configured on DT or platform data.
Signed-off-by: Huang Rui <ray.huang@amd.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>

Documentation/devicetree/bindings/usb/dwc3.txt

@@ -29,6 +29,9 @@ Optional properties:
  - snps,lfps_filter_quirk: when set core will filter LFPS reception.
  - snps,rx_detect_poll_quirk: when set core will disable a 400us delay to start
 			Polling LFPS after RX.Detect.
+ - snps,tx_de_emphasis_quirk: when set core will set Tx de-emphasis value.
+ - snps,tx_de_emphasis: the value driven to the PHY is controlled by the
+			LTSSM during USB3 Compliance mode.
 
 This is usually a subnode to DWC3 glue to which it is connected.
 

drivers/usb/dwc3/core.c

@@ -401,6 +401,9 @@ static void dwc3_phy_setup(struct dwc3 *dwc)
 	if (dwc->rx_detect_poll_quirk)
 		reg |= DWC3_GUSB3PIPECTL_RX_DETOPOLL;
 
+	if (dwc->tx_de_emphasis_quirk)
+		reg |= DWC3_GUSB3PIPECTL_TX_DEEPH(dwc->tx_de_emphasis);
+
 	dwc3_writel(dwc->regs, DWC3_GUSB3PIPECTL(0), reg);
 
 	mdelay(100);
@@ -720,6 +723,7 @@ static int dwc3_probe(struct platform_device *pdev)
 	struct resource		*res;
 	struct dwc3		*dwc;
 	u8			lpm_nyet_threshold;
+	u8			tx_de_emphasis;
 
 	int			ret;
 
@@ -778,6 +782,9 @@ static int dwc3_probe(struct platform_device *pdev)
 	/* default to highest possible threshold */
 	lpm_nyet_threshold = 0xff;
 
+	/* default to -3.5dB de-emphasis */
+	tx_de_emphasis = 1;
+
 	if (node) {
 		dwc->maximum_speed = of_usb_get_maximum_speed(node);
 		dwc->has_lpm_erratum = of_property_read_bool(node,
@@ -805,6 +812,11 @@ static int dwc3_probe(struct platform_device *pdev)
 				"snps,lfps_filter_quirk");
 		dwc->rx_detect_poll_quirk = of_property_read_bool(node,
 				"snps,rx_detect_poll_quirk");
+
+		dwc->tx_de_emphasis_quirk = of_property_read_bool(node,
+				"snps,tx_de_emphasis_quirk");
+		of_property_read_u8(node, "snps,tx_de_emphasis",
+				&tx_de_emphasis);
 	} else if (pdata) {
 		dwc->maximum_speed = pdata->maximum_speed;
 		dwc->has_lpm_erratum = pdata->has_lpm_erratum;
@@ -822,6 +834,10 @@ static int dwc3_probe(struct platform_device *pdev)
 		dwc->del_phy_power_chg_quirk = pdata->del_phy_power_chg_quirk;
 		dwc->lfps_filter_quirk = pdata->lfps_filter_quirk;
 		dwc->rx_detect_poll_quirk = pdata->rx_detect_poll_quirk;
+
+		dwc->tx_de_emphasis_quirk = pdata->tx_de_emphasis_quirk;
+		if (pdata->tx_de_emphasis)
+			tx_de_emphasis = pdata->tx_de_emphasis;
 	}
 
 	/* default to superspeed if no maximum_speed passed */
@@ -829,6 +845,7 @@ static int dwc3_probe(struct platform_device *pdev)
 		dwc->maximum_speed = USB_SPEED_SUPER;
 
 	dwc->lpm_nyet_threshold = lpm_nyet_threshold;
+	dwc->tx_de_emphasis = tx_de_emphasis;
 
 	ret = dwc3_core_get_phy(dwc);
 	if (ret)

drivers/usb/dwc3/core.h

@@ -185,6 +185,8 @@
 #define DWC3_GUSB3PIPECTL_SUSPHY	(1 << 17)
 #define DWC3_GUSB3PIPECTL_LFPSFILT	(1 << 9)
 #define DWC3_GUSB3PIPECTL_RX_DETOPOLL	(1 << 8)
+#define DWC3_GUSB3PIPECTL_TX_DEEPH_MASK	DWC3_GUSB3PIPECTL_TX_DEEPH(3)
+#define DWC3_GUSB3PIPECTL_TX_DEEPH(n)	((n) << 1)
 
 /* Global TX Fifo Size Register */
 #define DWC3_GTXFIFOSIZ_TXFDEF(n)	((n) & 0xffff)
@@ -695,6 +697,12 @@ struct dwc3_scratchpad_array {
  * @del_phy_power_chg_quirk: set if we enable delay phy power change quirk
  * @lfps_filter_quirk: set if we enable LFPS filter quirk
  * @rx_detect_poll_quirk: set if we enable rx_detect to polling lfps quirk
+ * @tx_de_emphasis_quirk: set if we enable Tx de-emphasis quirk
+ * @tx_de_emphasis: Tx de-emphasis value
+ * 	0	- -6dB de-emphasis
+ * 	1	- -3.5dB de-emphasis
+ * 	2	- No de-emphasis
+ * 	3	- Reserved
  */
 struct dwc3 {
 	struct usb_ctrlrequest	*ctrl_req;
@@ -810,6 +818,9 @@ struct dwc3 {
 	unsigned		del_phy_power_chg_quirk:1;
 	unsigned		lfps_filter_quirk:1;
 	unsigned		rx_detect_poll_quirk:1;
+
+	unsigned		tx_de_emphasis_quirk:1;
+	unsigned		tx_de_emphasis:2;
 };
 
 /* -------------------------------------------------------------------------- */

drivers/usb/dwc3/platform_data.h

@@ -36,4 +36,7 @@ struct dwc3_platform_data {
 	unsigned del_phy_power_chg_quirk:1;
 	unsigned lfps_filter_quirk:1;
 	unsigned rx_detect_poll_quirk:1;
+
+	unsigned tx_de_emphasis_quirk:1;
+	unsigned tx_de_emphasis:2;
 };