[BACKPORT,4.14.y,04/18] usb: dwc3: Allow disabling of metastability workaround
diff mbox series

Message ID 20190905161759.28036-5-mathieu.poirier@linaro.org
State New
Headers show
Series
  • Backport candidate from TI 4.14 product kernel
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Commit Message

Mathieu Poirier Sept. 5, 2019, 4:17 p.m. UTC
From: Roger Quadros <rogerq@ti.com>

commit 42bf02ec6e420e541af9a47437d0bdf961ca2972 upstream

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>
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
---
 Documentation/devicetree/bindings/usb/dwc3.txt | 2 ++
 drivers/usb/dwc3/core.c                        | 3 +++
 drivers/usb/dwc3/core.h                        | 3 +++
 drivers/usb/dwc3/gadget.c                      | 6 ++++--
 4 files changed, 12 insertions(+), 2 deletions(-)

Comments

Greg KH Sept. 10, 2019, 2:36 p.m. UTC | #1
On Thu, Sep 05, 2019 at 10:17:45AM -0600, Mathieu Poirier wrote:
> From: Roger Quadros <rogerq@ti.com>
> 
> commit 42bf02ec6e420e541af9a47437d0bdf961ca2972 upstream
> 
> 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]

Does the DT also need to get updated with this new id for this?  Is that
a separate patch somewhere?

thanks,

greg k-h
Mathieu Poirier Sept. 11, 2019, 2:01 p.m. UTC | #2
On Tue, 10 Sep 2019 at 08:36, Greg KH <greg@kroah.com> wrote:
>
> On Thu, Sep 05, 2019 at 10:17:45AM -0600, Mathieu Poirier wrote:
> > From: Roger Quadros <rogerq@ti.com>
> >
> > commit 42bf02ec6e420e541af9a47437d0bdf961ca2972 upstream
> >
> > 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]
>
> Does the DT also need to get updated with this new id for this?  Is that
> a separate patch somewhere?

The upstream commit is:

b8c9c6fa2002 ARM: dts: dra7: Disable USB metastability workaround for USB2

Should I just send the latter or you prefer a resend with both patches?

Thanks,
Mathieu

>
> thanks,
>
> greg k-h
Greg KH Nov. 11, 2019, 9:16 a.m. UTC | #3
On Wed, Sep 11, 2019 at 08:01:40AM -0600, Mathieu Poirier wrote:
> On Tue, 10 Sep 2019 at 08:36, Greg KH <greg@kroah.com> wrote:
> >
> > On Thu, Sep 05, 2019 at 10:17:45AM -0600, Mathieu Poirier wrote:
> > > From: Roger Quadros <rogerq@ti.com>
> > >
> > > commit 42bf02ec6e420e541af9a47437d0bdf961ca2972 upstream
> > >
> > > 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]
> >
> > Does the DT also need to get updated with this new id for this?  Is that
> > a separate patch somewhere?
> 
> The upstream commit is:
> 
> b8c9c6fa2002 ARM: dts: dra7: Disable USB metastability workaround for USB2
> 
> Should I just send the latter or you prefer a resend with both patches?

I've queued this up now, along with the rest of this series, thanks.

greg k-h

Patch
diff mbox series

diff --git a/Documentation/devicetree/bindings/usb/dwc3.txt b/Documentation/devicetree/bindings/usb/dwc3.txt
index 52fb41046b34..44e8bab159ad 100644
--- a/Documentation/devicetree/bindings/usb/dwc3.txt
+++ b/Documentation/devicetree/bindings/usb/dwc3.txt
@@ -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
diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
index 945330ea8d5c..9b093978bd24 100644
--- a/drivers/usb/dwc3/core.c
+++ b/drivers/usb/dwc3/core.c
@@ -1115,6 +1115,9 @@  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;
 
diff --git a/drivers/usb/dwc3/core.h b/drivers/usb/dwc3/core.h
index abd1142c9e4d..40bf0e0768d9 100644
--- a/drivers/usb/dwc3/core.h
+++ b/drivers/usb/dwc3/core.h
@@ -869,6 +869,7 @@  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.
  */
@@ -1025,6 +1026,8 @@  struct dwc3 {
 	unsigned		tx_de_emphasis_quirk:1;
 	unsigned		tx_de_emphasis:2;
 
+	unsigned		dis_metastability_quirk:1;
+
 	u16			imod_interval;
 };
 
diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
index 1b99d44e52b9..5916340c4162 100644
--- a/drivers/usb/dwc3/gadget.c
+++ b/drivers/usb/dwc3/gadget.c
@@ -2034,7 +2034,8 @@  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) {
@@ -3265,7 +3266,8 @@  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);