linux-kernel - [PATCH] usb: dwc3: gadget: Add 100uS delay after end transfer command without IOC

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Message-ID: <20230227232035.13759-1-quic_wcheng@quicinc.com>
Date:   Mon, 27 Feb 2023 15:20:35 -0800
From:   Wesley Cheng <quic_wcheng@...cinc.com>
To:     <gregkh@...uxfoundation.org>, <Thinh.Nguyen@...opsys.com>
CC:     <linux-kernel@...r.kernel.org>, <linux-usb@...r.kernel.org>,
        <quic_jackp@...cinc.com>, Wesley Cheng <quic_wcheng@...cinc.com>
Subject: [PATCH] usb: dwc3: gadget: Add 100uS delay after end transfer command without IOC

Previously, there was a 100uS delay inserted after issuing an end transfer
command for specific controller revisions.  This was due to the fact that
there was a GUCTL2 bit field which enabled synchronous completion of the
end transfer command once the CMDACT bit was cleared in the DEPCMD
register.  Since this bit does not exist for all controller revisions, add
the delay back in.

An issue was seen where the USB request buffer was unmapped while the DWC3
controller was still accessing the TRB.  However, it was confirmed that the
end transfer command was successfully submitted. (no end transfer timeout)
In situations, such as dwc3_gadget_soft_disconnect() and
__dwc3_gadget_ep_disable(), the dwc3_remove_request() is utilized, which
will issue the end transfer command, and follow up with
dwc3_gadget_giveback().  At least for the USB ep disable path, it is
required for any pending and started requests to be completed and returned
to the function driver in the same context of the disable call.  Without
the GUCTL2 bit, it is not ensured that the end transfer is completed before
the buffers are unmapped.

Signed-off-by: Wesley Cheng <quic_wcheng@...cinc.com>
---
 drivers/usb/dwc3/gadget.c | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
index 3c63fa97a680..a4c02e4f7f7c 100644
--- a/drivers/usb/dwc3/gadget.c
+++ b/drivers/usb/dwc3/gadget.c
@@ -1699,6 +1699,7 @@ static int __dwc3_gadget_get_frame(struct dwc3 *dwc)
  */
 static int __dwc3_stop_active_transfer(struct dwc3_ep *dep, bool force, bool interrupt)
 {
+	struct dwc3 *dwc = dep->dwc;
 	struct dwc3_gadget_ep_cmd_params params;
 	u32 cmd;
 	int ret;
@@ -1722,10 +1723,13 @@ static int __dwc3_stop_active_transfer(struct dwc3_ep *dep, bool force, bool int
 	WARN_ON_ONCE(ret);
 	dep->resource_index = 0;

-	if (!interrupt)
+	if (!interrupt) {
+		if (DWC3_IP_IS(DWC31) || DWC3_VER_IS_PRIOR(DWC3, 310A))
+			udelay(100);
 		dep->flags &= ~DWC3_EP_TRANSFER_STARTED;
-	else if (!ret)
+	} else if (!ret) {
 		dep->flags |= DWC3_EP_END_TRANSFER_PENDING;
+	}

 	dep->flags &= ~DWC3_EP_DELAY_STOP;
 	return ret;
@@ -3774,7 +3778,11 @@ void dwc3_stop_active_transfer(struct dwc3_ep *dep, bool force,
 	 * enabled, the EndTransfer command will have completed upon
 	 * returning from this function.
 	 *
-	 * This mode is NOT available on the DWC_usb31 IP.
+	 * This mode is NOT available on the DWC_usb31 IP.  In this
+	 * case, if the IOC bit is not set, then delay by 100uS
+	 * after issuing the EndTransfer command.  This allows for the
+	 * controller to handle the command completely before DWC3
+	 * remove requests attempts to unmap USB request buffers.
 	 */

 	__dwc3_stop_active_transfer(dep, force, interrupt);