linux-kernel - Re: [PATCH v10 3/6] usb: dwc3: Resize TX FIFOs to meet EP bursting requirements

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Message-ID: <1a979c61-e996-b94a-c986-a9721d3b3297@codeaurora.org>
Date:   Mon, 21 Jun 2021 22:27:13 -0700
From:   Wesley Cheng <wcheng@...eaurora.org>
To:     Greg KH <gregkh@...uxfoundation.org>
Cc:     balbi@...nel.org, robh+dt@...nel.org, agross@...nel.org,
        bjorn.andersson@...aro.org, frowand.list@...il.com,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        jackp@...eaurora.org, fntoth@...il.com,
        heikki.krogerus@...ux.intel.com, andy.shevchenko@...il.com
Subject: Re: [PATCH v10 3/6] usb: dwc3: Resize TX FIFOs to meet EP bursting
 requirements



On 6/17/2021 4:10 AM, Greg KH wrote:
> On Thu, Jun 17, 2021 at 02:58:16AM -0700, Wesley Cheng wrote:
>> +static int dwc3_gadget_check_config(struct usb_gadget *g, unsigned long ep_map)
>> +{
>> +	struct dwc3 *dwc = gadget_to_dwc(g);
>> +	unsigned long in_ep_map;
>> +	int fifo_size = 0;
>> +	int ram1_depth;
>> +	int ep_num;
>> +
>> +	if (!dwc->do_fifo_resize)
>> +		return 0;
>> +
>> +	/* Only interested in the IN endpoints */
>> +	in_ep_map = ep_map >> 16;

Hi Greg,

> 
> Wait, this "map" is split up into 16/16 somehow?  So it's only 32bits
> big?
>

Yes, correct. Upper 16 carries IN eps, lower 16 carries OUT eps.  Will
fix that based off your other comment.

> Where did you document this map structure?  Why is it needed at all, you
> have the gadget, don't you have access to the full list of endpoints
> here as well?
> 
> confused,
> 

Unfortunately, we do not have the entire list of endpoints for each
function until the composite driver receives the SET_CONFIG packet from
the host.  By this time, if we incorrectly allowed the configuration to
start enumeration w/ the host, and there were some EPs which have no
FIFO memory allocated, that would lead to those interfaces/functions
being broken.

The USB UDC driver does have the in_epnum and out_epnum, but those are
currently only being incremented in case we don't match EPs by string.
(in usb_ep_autoconfig_ss())

Thanks
Wesley Cheng

> greg k-h
> 

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