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Commit 42bf02ec authored by Roger Quadros's avatar Roger Quadros Committed by Felipe Balbi
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usb: dwc3: Allow disabling of metastability workaround 



Some platforms (e.g. TI's DRA7 USB2 instance) have more trouble
with the metastability workaround as it supports only
a High-Speed PHY and the PHY can enter into an Erratic state [1]
when the controller is set in SuperSpeed mode as part of
the metastability workaround.

This causes upto 2 seconds delay in enumeration on DRA7's USB2
instance in gadget mode.

If these platforms can be better off without the workaround,
provide a device tree property to suggest that so the workaround
is avoided.

[1] Device mode enumeration trace showing PHY Erratic Error.
     irq/90-dwc3-969   [000] d...    52.323145: dwc3_event: event (00000901): Erratic Error [U0]
     irq/90-dwc3-969   [000] d...    52.560646: dwc3_event: event (00000901): Erratic Error [U0]
     irq/90-dwc3-969   [000] d...    52.798144: dwc3_event: event (00000901): Erratic Error [U0]

Signed-off-by: default avatarRoger Quadros <rogerq@ti.com>
Signed-off-by: default avatarFelipe Balbi <felipe.balbi@linux.intel.com>
parent d855e08c

Documentation/devicetree/bindings/usb/dwc3.txt

+2 −0
Original line number Diff line number Diff line
@@ -47,6 +47,8 @@ Optional properties: 
			from P0 to P1/P2/P3 without delay.

 - snps,dis-tx-ipgap-linecheck-quirk: when set, disable u2mac linestate check

			during HS transmit.

 - snps,dis_metastability_quirk: when set, disable metastability workaround.

			CAUTION: use only if you are absolutely sure of it.

 - snps,is-utmi-l1-suspend: true when DWC3 asserts output signal

			utmi_l1_suspend_n, false when asserts utmi_sleep_n

 - snps,hird-threshold: HIRD threshold

drivers/usb/dwc3/core.c

+3 −0
Original line number Diff line number Diff line
@@ -1062,6 +1062,9 @@ static void dwc3_get_properties(struct dwc3 *dwc) 
	device_property_read_u32(dev, "snps,quirk-frame-length-adjustment",

				 &dwc->fladj);



	dwc->dis_metastability_quirk = device_property_read_bool(dev,

				"snps,dis_metastability_quirk");



	dwc->lpm_nyet_threshold = lpm_nyet_threshold;

	dwc->tx_de_emphasis = tx_de_emphasis;

drivers/usb/dwc3/core.h

+3 −0
Original line number Diff line number Diff line
@@ -856,6 +856,7 @@ struct dwc3_scratchpad_array { 
 * 	1	- -3.5dB de-emphasis

 * 	2	- No de-emphasis

 * 	3	- Reserved

 * @dis_metastability_quirk: set to disable metastability quirk.

 * @imod_interval: set the interrupt moderation interval in 250ns

 *                 increments or 0 to disable.

 */
@@ -1008,6 +1009,8 @@ struct dwc3 { 
	unsigned		tx_de_emphasis_quirk:1;

	unsigned		tx_de_emphasis:2;



	unsigned		dis_metastability_quirk:1;



	u16			imod_interval;

};

drivers/usb/dwc3/gadget.c

+4 −2
Original line number Diff line number Diff line
@@ -2005,7 +2005,8 @@ static void dwc3_gadget_set_speed(struct usb_gadget *g, 
	 * STAR#9000525659: Clock Domain Crossing on DCTL in

	 * USB 2.0 Mode

	 */

	if (dwc->revision < DWC3_REVISION_220A) {

	if (dwc->revision < DWC3_REVISION_220A &&

	    !dwc->dis_metastability_quirk) {

		reg |= DWC3_DCFG_SUPERSPEED;

	} else {

		switch (speed) {
@@ -3224,7 +3225,8 @@ int dwc3_gadget_init(struct dwc3 *dwc) 
	 * is less than super speed because we don't have means, yet, to tell

	 * composite.c that we are USB 2.0 + LPM ECN.

	 */

	if (dwc->revision < DWC3_REVISION_220A)

	if (dwc->revision < DWC3_REVISION_220A &&

	    !dwc->dis_metastability_quirk)

		dev_info(dwc->dev, "changing max_speed on rev %08x\n",

				dwc->revision);