Re: [PATCH v7 00/24] usb: dwc3: part 2, make the resynced code work

On Wed Aug 26, 2026 at 1:59 PM IST, Anders Roxell wrote:
> On 2026-08-25 15:12, Anshul Dalal wrote:
>> On Mon, 24 Aug 2026 17:41:09 +0200, Anders Roxell <[email protected]> wrote:
>> > [...]
>> > dwc2 with and without DM_USB_GADGET, at91_udc, atmel_usba_udc, ci_udc,
>> > musb-new and mtu3. 17 boards in total.
>> > 
>> > DFU is tested on hardware on BeagleBoard-X15, and on BeaglePlay by
>> > Anshul. ci_udc is tested on an i.MX93 board with ums. The rest is build
>> > tested only.
>> 
>> Hi Anders,
>> 
>> Thanks for reworking the series, I was able to get DFU boot to work properly
>> and the usb devices are being discovered properly too.
>> 
>> Though I ran into an issue while using ums with your patches as the host isn't
>> able to detect the connected device. With default logs I only see a
>> '\dwc3-generic-peripheral usb@31000000: unknown endpoint event 0'.
>> 
>> Further debug logs are below on TI's AM62p EVM:
>> 
>> @    => ums mmc 1
>> @    UMS: LUN 0, dev mmc 1, hwpart 0, sector 0x0, count 0x3b72400
>> @    g_dnl_register: g_dnl_driver.name = usb_dnl_ums
>> @    g_dnl_bind: gadget: 0x00000000fde7fb68 cdev: 0x00000000fde5cdd0
>> @    usb_add_config: adding config #1 'usb_dnload'/00000000fde83cc0
>> @    g_dnl_do_config: configuration: 0x00000000fde83cc0 composite dev: 0x00000000fde5cdd0
>> @    adding 'Mass Storage Function'/00000000fde5c110 to config 'usb_dnload'/00000000fde83cc0
>> @    cfg 1/00000000fde83cc0 speeds: high full
>> @    usb_add_config: interface 0 = Mass Storage Function/00000000fde5c110
>> @    g_dnl_bind: calling usb_gadget_connect for controller 'dwc3-gadget'
>> @    usb_dnl_ums: ready
>> @    -dwc3-generic-peripheral usb@31000000: unknown endpoint event 0
>> @    |set_config: high speed config #1: usb_dnload
>> @    \non-core control reqa1.fe v0000 i0000 l1
>> 
>> I observed a similar issue on the beagleplay too. Regards!
>
> Hi Anshul,
>
> I could reproduce it on my BeagleBoard-X15. First I only saw it connect
> and got happy, so I forgot to look for the disk. It never shows up, and
> the host gives up after 20 seconds.
>
> The resync dropped the cache maintenance in dwc3 gadget.c. The
> controller reads a stale trb and nothing moves, that is your "unknown
> endpoint event 0". DFU still worked because it only uses ep0.
>
> With the diff below the disk shows up and 64 MiB reads back correctly.
> It applies on v7.
>
> Can you try ums on AM62p and BeaglePlay? Please let me know how it goes
> before I send the next version.

Thanks for the fix Anders, the block device shows up properly now.
However the 'dwc3-generic-peripheral usb@31000000: unknown endpoint
event 0' error log remains, is this expected?

Regards,
Anshul

>
>
> Cheers,
> Anders
>
> diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
> index 028ebd9b9c79..fd0ae9e3e092 100644
> --- a/drivers/usb/dwc3/gadget.c
> +++ b/drivers/usb/dwc3/gadget.c
> @@ -228,6 +228,10 @@ void dwc3_gadget_giveback(struct dwc3_ep *dep, struct dwc3_request *req,
>  	dwc3_gadget_del_and_unmap_request(dep, req, status);
>  	req->status = DWC3_REQUEST_STATUS_COMPLETED;
>  
> +	if (req->request.dma && req->request.length)
> +		dwc3_invalidate_cache((uintptr_t)req->request.dma,
> +				      req->request.length);
> +
>  	spin_unlock(&dwc->lock);
>  	usb_gadget_giveback_request(&dep->endpoint, &req->request);
>  	spin_lock(&dwc->lock);
> @@ -1382,9 +1386,12 @@ static void dwc3_prepare_one_trb(struct dwc3_ep *dep,
>  	 * controller to observe the HWO bit set prematurely.
>  	 * Add a write memory barrier to prevent CPU re-ordering.
>  	 */
> -	// FIXME wmb();
> +	wmb();
>  	trb->ctrl |= DWC3_TRB_CTRL_HWO;
>  
> +	dwc3_flush_cache((uintptr_t)dma, trb_length);
> +	dwc3_flush_cache((uintptr_t)trb, sizeof(*trb));
> +
>  	dwc3_ep_inc_enq(dep);
>  }
>  
> @@ -3153,6 +3160,8 @@ static int dwc3_gadget_ep_reclaim_completed_trb(struct dwc3_ep *dep,
>  {
>  	unsigned int		count;
>  
> +	dwc3_invalidate_cache((uintptr_t)trb, sizeof(*trb));
> +
>  	dwc3_ep_inc_deq(dep);
>  
>  	req->num_trbs--;
> @@ -4181,7 +4190,7 @@ static irqreturn_t dwc3_process_event_buf(struct dwc3_event_buffer *evt)
>  	 * Add an explicit write memory barrier to make sure that the update of
>  	 * clearing DWC3_EVENT_PENDING is observed in dwc3_check_event_buf()
>  	 */
> -	// FIXME wmb();
> +	wmb();
>  
>  	if (dwc->imod_interval) {
>  		dwc3_writel(dwc->regs, DWC3_GEVNTCOUNT(0), DWC3_GEVNTCOUNT_EHB);