linux-kernel - Re: [PATCH v3] usb: dwc3: gadget: Add 1ms delay after end transfer command without IOC

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Message-ID: <20230228232846.GB3727894@hu-jackp-lv.qualcomm.com>
Date:   Tue, 28 Feb 2023 15:28:46 -0800
From:   Jack Pham <quic_jackp@...cinc.com>
To:     Wesley Cheng <quic_wcheng@...cinc.com>
CC:     <gregkh@...uxfoundation.org>, <Thinh.Nguyen@...opsys.com>,
        <linux-kernel@...r.kernel.org>, <linux-usb@...r.kernel.org>
Subject: Re: [PATCH v3] usb: dwc3: gadget: Add 1ms delay after end transfer
 command without IOC

On Tue, Feb 28, 2023 at 12:24:18PM -0800, 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@...cinc.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))

How about a little more succinctly:

		if (!DWC3_IP_IS(DWC3) || DWC3_VER_IS_PRIOR(DWC3, 310A))
?

Jack