linux-kernel - Re: [PATCH v2 2/3] usb: dwc3: gadget: Add support for snps,reserved-endpoints property

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Message-ID: <20250213011736.orc23wbgvjoybrbq@synopsys.com>
Date: Thu, 13 Feb 2025 01:17:41 +0000
From: Thinh Nguyen <Thinh.Nguyen@...opsys.com>
To: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
CC: Thinh Nguyen <Thinh.Nguyen@...opsys.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Felipe Balbi <balbi@...nel.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley <conor+dt@...nel.org>, Ferry Toth <fntoth@...il.com>
Subject: Re: [PATCH v2 2/3] usb: dwc3: gadget: Add support for
 snps,reserved-endpoints property

On Wed, Feb 12, 2025, Andy Shevchenko wrote:
> On Wed, Feb 12, 2025 at 12:36:04PM +0200, Andy Shevchenko wrote:
> > On Wed, Feb 12, 2025 at 01:10:17AM +0000, Thinh Nguyen wrote:
> > > On Mon, Feb 03, 2025, Andy Shevchenko wrote:
> 
> ...
> 
> > > > static bool dwc3_gadget_endpoint_trbs_complete(struct dwc3_ep *dep,
> > 
> > > >  		for (i = 0; i < DWC3_ENDPOINTS_NUM; i++) {
> > > >  			dep = dwc->eps[i];
> > > > +			if (!dep)
> > > > +				continue;
> > > 
> > > It should be fine to ignore this check here. Something must be really
> > > wrong if there's an interrupt pointing to an endpoint that we shouldn't
> > > be touching. If we do add a check, we should print a warn or something
> > > here. But that should be a patch separate from this.
> > 
> > Theoretically everything is possible as it may be HW integration bug,
> > for example. But are you asking about separate patch even from the rest
> > of the checks? Please, elaborate what do you want to see.
> 
> Re-reading the code again, I don't understand. If we get to this loop
> ever (theoretically it might be an old IP with the reserved endpoints),
> we crash the kernel on the first gap in the array. And since the function
> is called on an endpoint, it doesn't mean that all endpoints are allocated,
> so I do not see the justification to issue a warning here.
> Or do you imply that DWC3_VER_IS_PRIOR(DWC3, 183A) may not have an HW
> integration similar to what we have on Intel Merrifield?
> 
> For now I'm going to leave this check as is.

Oops, you are correct. I read this as the same logic as below.

> 
> ...
> 
> > > > static void dwc3_endpoint_interrupt(struct dwc3 *dwc,
> > 
> > > >  	dep = dwc->eps[epnum];
> > > > +	if (!dep)
> > > > +		return;
> > > 
> > > Same here.
> 
> Here I agree and I will add a warning message. Indeed, if we get and interrupt
> for undefined endpoint, something is not correct.
> 

BR,
Thinh