RE: [PATCH 3/3] usb: aspeed-vhub: fix ep0 OUT ack received wrong length issue

[Neal Liu <neal_liu@aspeedtech.com>]

> -----Original Message-----
> From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
> Sent: Tuesday, November 30, 2021 7:49 AM
> To: Neal Liu <neal_liu@aspeedtech.com>; Felipe Balbi <balbi@kernel.org>;
> Greg Kroah-Hartman <gregkh@linuxfoundation.org>; Joel Stanley
> <joel@jms.id.au>; Andrew Jeffery <andrew@aj.id.au>; Cai Huoqing
> <caihuoqing@baidu.com>; Tao Ren <rentao.bupt@gmail.com>; Julia Lawall
> <julia.lawall@inria.fr>; kernel test robot <lkp@intel.com>; Sasha Levin
> <sashal@kernel.org>; linux-usb@vger.kernel.org; linux-kernel@vger.kernel.org;
> linux-arm-kernel@lists.infradead.org; linux-aspeed@lists.ozlabs.org
> Cc: BMC-SW <BMC-SW@aspeedtech.com>
> Subject: Re: [PATCH 3/3] usb: aspeed-vhub: fix ep0 OUT ack received wrong
> length issue
> 
> On Fri, 2021-11-26 at 19:09 +0800, Neal Liu wrote:
> >
> > diff --git a/drivers/usb/gadget/udc/aspeed-vhub/ep0.c
> > b/drivers/usb/gadget/udc/aspeed-vhub/ep0.c
> > index 74ea36c19b1e..bea9cbb191a2 100644
> > --- a/drivers/usb/gadget/udc/aspeed-vhub/ep0.c
> > +++ b/drivers/usb/gadget/udc/aspeed-vhub/ep0.c
> > @@ -251,6 +251,13 @@ static void ast_vhub_ep0_do_receive(struct
> > ast_vhub_ep *ep, struct ast_vhub_req
> >  		len = remain;
> >  		rc = -EOVERFLOW;
> >  	}
> > +
> > +	/* HW return wrong data len */
> > +	if (len < ep->ep.maxpacket && len != remain) {
> > +		EPDBG(ep, "using expected data len instead\n");
> > +		len = remain;
> > +	}
> > +
> 
> Wow, that is a nasty hw bug ! Patch looks good, I had to swap some of that
> logic back into my brain but it looks like it won't break any normal case :-)
> 
> Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
> 
> Cheers,
> Ben.

Thanks for your review.
-Neal