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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: Roger Quadros <rogerq@ti.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>
This commit is contained in:
Roger Quadros 2017-10-31 15:11:55 +02:00 committed by Felipe Balbi
parent d855e08cf6
commit 42bf02ec6e
4 changed files with 12 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
Documentation/devicetree/bindings/usb/dwc3.txt
View File

@ -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

3
drivers/usb/dwc3/core.c
View File

@ -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;

3
drivers/usb/dwc3/core.h
View File

@ -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;
};

6
drivers/usb/dwc3/gadget.c
View File

@ -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);