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List:       linux-usb
Subject:    Re: [PATCH v3] usb: dwc3: gadget: Add 1ms delay after end transfer command without IOC
From:       Thinh Nguyen <Thinh.Nguyen () synopsys ! com>
Date:       2023-02-28 23:44:06
Message-ID: 20230228234404.b6uvjpt63iz7cxkx () synopsys ! com
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On Tue, Feb 28, 2023, Wesley Cheng wrote:
> 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, and increase the duration to 1ms for the controller to
> complete the command.
> 
> 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@quicinc.com>
> ---
> Changes in v3:
> - Fixed subject title and modified commit text to reference the new 1ms
> delay
> 
> Changes in v2:
> - Increase delay value to 1ms
> - Make this applicable to DWC32 revisions as well
> 
> drivers/usb/dwc3/gadget.c | 15 ++++++++++++---
> 1 file changed, 12 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
> index 3c63fa97a680..15adf07a4df4 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 +1723,14 @@ 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(DWC32) || DWC3_IP_IS(DWC31) ||
> +			DWC3_VER_IS_PRIOR(DWC3, 310A))
> +			mdelay(1);
> 		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 +3779,11 @@ 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

100us -> 1ms

> +	 * 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);

BR,
Thinh


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