[PATCH v3 2/3] usb: dwc3: gadget: Add support for disabling SS instances in park mode

[Neil Armstrong]

In certain circumstances, the XHCI SuperSpeed instance in park mode
can fail to recover, thus on Amlogic G12A/G12B/SM1 SoCs when there is high
load on the single XHCI SuperSpeed instance, the controller can crash like:
 xhci-hcd xhci-hcd.0.auto: xHCI host not responding to stop endpoint command.
 xhci-hcd xhci-hcd.0.auto: Host halt failed, -110
 xhci-hcd xhci-hcd.0.auto: xHCI host controller not responding, assume dead
 xhci-hcd xhci-hcd.0.auto: xHCI host not responding to stop endpoint command.
 hub 2-1.1:1.0: hub_ext_port_status failed (err = -22)
 xhci-hcd xhci-hcd.0.auto: HC died; cleaning up
 usb 2-1.1-port1: cannot reset (err = -22)

Setting the PARKMODE_DISABLE_SS bit in the DWC3_USB3_GUCTL1 mitigates
the issue. The bit is described as :
"When this bit is set to '1' all SS bus instances in park mode are disabled"

Synopsys explains in [1]:
The GUCTL1.PARKMODE_DISABLE_SS is only available in
dwc_usb3 controller running in host mode.
This should not be set for other IPs.
This can be disabled by default based on IP, but I recommend to have a
property to enable this feature for devices that need this.

[1] https://lore.kernel.org/linux-usb/45212db9-e366-2669-5c0a-3c5bd06287f6@xxxxxxxxxxxx

CC: Dongjin Kim <tobetter@xxxxxxxxx>
Cc: Jianxin Pan <jianxin.pan@xxxxxxxxxxx>
Cc: Thinh Nguyen <thinhn@xxxxxxxxxxxx>
Cc: Jun Li <lijun.kernel@xxxxxxxxx>
Reported-by: Tim <elatllat@xxxxxxxxx>
Signed-off-by: Neil Armstrong <narmstrong@xxxxxxxxxxxx>
---
 drivers/usb/dwc3/core.c | 5 +++++
 drivers/usb/dwc3/core.h | 4 ++++
 2 files changed, 9 insertions(+)

diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
index 1d85c42b9c67..43bd5b1ea9e2 100644
--- a/drivers/usb/dwc3/core.c
+++ b/drivers/usb/dwc3/core.c
@@ -1029,6 +1029,9 @@ static int dwc3_core_init(struct dwc3 *dwc)
 		if (dwc->dis_tx_ipgap_linecheck_quirk)
 			reg |= DWC3_GUCTL1_TX_IPGAP_LINECHECK_DIS;
 
+		if (dwc->parkmode_disable_ss_quirk)
+			reg |= DWC3_GUCTL1_PARKMODE_DISABLE_SS;
+
 		dwc3_writel(dwc->regs, DWC3_GUCTL1, reg);
 	}
 
@@ -1342,6 +1345,8 @@ static void dwc3_get_properties(struct dwc3 *dwc)
 				"snps,dis-del-phy-power-chg-quirk");
 	dwc->dis_tx_ipgap_linecheck_quirk = device_property_read_bool(dev,
 				"snps,dis-tx-ipgap-linecheck-quirk");
+	dwc->parkmode_disable_ss_quirk = device_property_read_bool(dev,
+				"snps,parkmode-disable-ss-quirk");
 
 	dwc->tx_de_emphasis_quirk = device_property_read_bool(dev,
 				"snps,tx_de_emphasis_quirk");
diff --git a/drivers/usb/dwc3/core.h b/drivers/usb/dwc3/core.h
index 77c4a9abe365..3ecc69c5b150 100644
--- a/drivers/usb/dwc3/core.h
+++ b/drivers/usb/dwc3/core.h
@@ -249,6 +249,7 @@
 #define DWC3_GUCTL_HSTINAUTORETRY	BIT(14)
 
 /* Global User Control 1 Register */
+#define DWC3_GUCTL1_PARKMODE_DISABLE_SS	BIT(17)
 #define DWC3_GUCTL1_TX_IPGAP_LINECHECK_DIS	BIT(28)
 #define DWC3_GUCTL1_DEV_L1_EXIT_BY_HW	BIT(24)
 
@@ -1024,6 +1025,8 @@ struct dwc3_scratchpad_array {
  *			change quirk.
  * @dis_tx_ipgap_linecheck_quirk: set if we disable u2mac linestate
  *			check during HS transmit.
+ * @parkmode_disable_ss_quirk: set if we need to disable all SuperSpeed
+ *			instances in park mode.
  * @tx_de_emphasis_quirk: set if we enable Tx de-emphasis quirk
  * @tx_de_emphasis: Tx de-emphasis value
  * 	0	- -6dB de-emphasis
@@ -1215,6 +1218,7 @@ struct dwc3 {
 	unsigned		dis_u2_freeclk_exists_quirk:1;
 	unsigned		dis_del_phy_power_chg_quirk:1;
 	unsigned		dis_tx_ipgap_linecheck_quirk:1;
+	unsigned		parkmode_disable_ss_quirk:1;
 
 	unsigned		tx_de_emphasis_quirk:1;
 	unsigned		tx_de_emphasis:2;
-- 
2.22.0