Re: [PATCH] usb: dwc3: core: Do not perform GCTL_CORE_SOFTRESET during bootup

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On 7/14/2022 6:36 AM, Thinh Nguyen wrote:
On 7/12/2022, Rohith Kollalsi wrote:
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>
---
   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..7ce0e033d755 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 zero, do not perform GCTL_CORESOFTRESET.

The line above doesn't really explain why. Can you rephrase it to
something like this or the equivalent:
"When current_dr_role is not set, there's no role switching. Only
perform GCTL.CoreSoftReset when there's DRD role switching."

Thanks,
Thinh

Thanks for the review Thinh, I have updated the next version of the patch with this suggestion.

Thanks,
Rohith


+	 * Perform it only for DRD host or device mode.
+	 */
+	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);




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