According to the programming guide, it is recommended to
perform a GCTL_CORE_SOFTRESET only when switching the mode
from device to host or host to device. However, it is found
that during bootup when __dwc3_set_mode() is called for the
first time, GCTL_CORESOFTRESET is done with suspendable bit(BIT 17)
of DWC3_GUSB3PIPECTL set. This some times leads to issues
like controller going into bad state and controller registers
reading value zero. Until GCTL_CORESOFTRESET is done and
run/stop bit is set core initialization is not complete.
Setting suspendable bit of DWC3_GUSB3PIPECTL and then
performing GCTL_CORESOFTRESET is therefore not recommended.
Avoid this by only performing the reset if current_dr_role is set,
that is, when doing subsequent role switching.
Fixes: f88359e1588b ("usb: dwc3: core: Do core softreset when switch mode")
Signed-off-by: Rohith Kollalsi <quic_rkollals@xxxxxxxxxxx>
---
v2: Explaining the scenario in a better way in the comment before
GCTL.CoreSoftReset.
drivers/usb/dwc3/core.c | 10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)
diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
index 050b2ba5986d..c5c238ab3083 100644
--- a/drivers/usb/dwc3/core.c
+++ b/drivers/usb/dwc3/core.c
@@ -158,9 +158,13 @@ static void __dwc3_set_mode(struct work_struct *work)
break;
}
- /* For DRD host or device mode only */
- if ((DWC3_IP_IS(DWC3) || DWC3_VER_IS_PRIOR(DWC31, 190A)) &&
- dwc->desired_dr_role != DWC3_GCTL_PRTCAP_OTG) {
+ /*
+ * When current_dr_role is not set, there's no role switching.
+ * Only perform GCTL.CoreSoftReset when there's DRD role switching.
+ */
+ if (dwc->current_dr_role && ((DWC3_IP_IS(DWC3) ||
+ DWC3_VER_IS_PRIOR(DWC31, 190A)) &&
+ dwc->desired_dr_role != DWC3_GCTL_PRTCAP_OTG)) {
reg = dwc3_readl(dwc->regs, DWC3_GCTL);
reg |= DWC3_GCTL_CORESOFTRESET;
dwc3_writel(dwc->regs, DWC3_GCTL, reg);
--
2.17.1
