Message-ID: <04885952-caa3-46b5-bd20-7e10897d8aaa@quicinc.com>
Date: Fri, 27 Sep 2024 20:55:01 +0530
From: AKASH KUMAR <quic_akakum@...cinc.com>
To: Thinh Nguyen <Thinh.Nguyen@...opsys.com>
CC: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Felipe Balbi
	<balbi@...nel.org>, Jack Pham <quic_jackp@...cinc.com>,
        "kernel@...cinc.com"
	<kernel@...cinc.com>,
        Wesley Cheng <quic_wcheng@...cinc.com>,
        "Laurent
 Pinchart" <laurent.pinchart@...asonboard.com>,
        Daniel Scally
	<dan.scally@...asonboard.com>,
        Vijayavardhan Vennapusa
	<quic_vvreddy@...cinc.com>,
        Krishna Kurapati <quic_kriskura@...cinc.com>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3] usb: dwc3: gadget: Refine the logic for resizing Tx
 FIFOs

Hi Thinh,

On 9/27/2024 3:46 AM, Thinh Nguyen wrote:
> Hi Akash,
>
> Sorry for the delay response.
>
> On Wed, Sep 18, 2024, AKASH KUMAR wrote:
>> Hi Thinh,
>>
>> On 9/18/2024 4:10 AM, Thinh Nguyen wrote:
>>> On Tue, Sep 17, 2024, Akash Kumar wrote:
>>>> The current logic is rigid, setting num_fifos to fixed values:
>>>>
>>>> 3 for any maxburst greater than 1.
>>>> tx_fifo_resize_max_num for maxburst greater than 6.
>>>> Additionally, it did not differentiate much between bulk and
>>>> isochronous transfers, applying similar logic to both.
>>>>
>>>> The new logic is more dynamic and tailored to the specific needs of
>>>> bulk and isochronous transfers:
>>>>
>>>> Bulk Transfers: Ensures that num_fifos is optimized by considering
>>>> both the maxburst value and the maximum allowed number of FIFOs
>>>> based on the DT property tx_fifo_resize_max_num and the maximum
>>>> packet multiplier for HS.
>>>>
>>>> Isochronous Transfers: Ensures that num_fifos is sufficient by
>>>> considering the maximum packet multiplier for HS and maxburst for SS,
>>>> along with a constraint with the DT property tx_fifo_resize_max_num.
>>>>
>>>> This change aims to optimize the allocation of Tx FIFOs for both bulk
>>>> and isochronous endpoints, potentially improving data transfer
>>>> efficiency and overall performance. It also enhances support for all
>>>> use cases, which can be tweaked with DT parameters and the
>>> You should clarify that this is only verified on your specific platform
>>> and specific application. It may not be applicable to all cases.
>>> However, we try our best to make it so. Please reword as such. The
>>> commit message makes it seems that this will work for all cases.
>> Sure will rephrase it, but i believe since it can be customized based on
>> maxpacket and
>> maxburst , anyone can choose his desired fifo size and since we will be get
> The logic depends on what the endpoint's setting will be. The endpoint
> setting is not some runtime field that the user can set. The point I
> want to make is that this is validated on your platform, but it may not
> work for all cases. (e.g. this may use up more available txfifo for
> other endpoints on a more fifo constraint platform)
Ack.
>
>> maxp as 1 (for any streaming packet < 2048)  and additional +1 which we are
>> appending which
>> makes minimum 2k fifo size for HS which should be  sufficient for HS
>> transfers and it can increased with maxpacket when increased to 2k or 3k.
>> Similar with  maxburst for >= SS.
>>>> endpoint’s maxburst and maxpacket
>>>>
>>>> Signed-off-by: Akash Kumar <quic_akakum@...cinc.com>
>>>> ---
>>>>    Changes for v3:
>>>>    Redefine logic for resizing tx fifos,added check based on
>>>>    operating speed and used maxp for HS and maxburst for SS
>>>>    and defined max allocation based on dt property.
>>>>
>>>>    Changes for v2:
>>>>    Redefine logic for resizing tx fifos, handled fifo based on
>>>>    minimum of maxp and maxburts.
>>>>
>>>>    Changes for v1:
>>>>    Added additional condition to allocate tx fifo for hs isoc
>>>>    eps, keeping the other resize logic same.
>>>> ---
>>>>    drivers/usb/dwc3/gadget.c | 18 +++++++++++-------
>>>>    1 file changed, 11 insertions(+), 7 deletions(-)
>>>>
>>>> diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
>>>> index 89fc690fdf34..7557bd0053a7 100644
>>>> --- a/drivers/usb/dwc3/gadget.c
>>>> +++ b/drivers/usb/dwc3/gadget.c
>>>> @@ -778,15 +778,19 @@ static int dwc3_gadget_resize_tx_fifos(struct dwc3_ep *dep)
>>>>    	ram1_depth = DWC3_RAM1_DEPTH(dwc->hwparams.hwparams7);
>>>> -	if ((dep->endpoint.maxburst > 1 &&
>>>> -	     usb_endpoint_xfer_bulk(dep->endpoint.desc)) ||
>>>> -	    usb_endpoint_xfer_isoc(dep->endpoint.desc))
>>>> -		num_fifos = 3;
>>>> +	if (dwc->gadget->speed <= USB_SPEED_HIGH &&
>>>> +	    (usb_endpoint_xfer_bulk(dep->endpoint.desc) ||
>>>> +	     usb_endpoint_xfer_isoc(dep->endpoint.desc)))
>>>> +		num_fifos = min_t(unsigned int,
>>>> +				  usb_endpoint_maxp_mult(dep->endpoint.desc) + 1,
>>> This logic looks wrong. This implies maxp_mult is applicable to bulk and
>>> that it's also applicable to speed below highspeed, which it isn't.
>> This is to make it generic as 2k fifo should be suffiecient for bulk eps in
>> HS as explained above
>> and we can increase maxpacket size when required which will incresse fifo
>> size as well.
> I think you missed my point here. The maxp_mult should only be checked
> against isoc and only for highspeed. Please split it out. Make it clear
> that the bulk uses 2k txfifo for highspeed and below.

Sure let me update.

>
>>>> +				  dwc->tx_fifo_resize_max_num);
>>>> -	if (dep->endpoint.maxburst > 6 &&
>>>> +	if (dwc->gadget->speed > USB_SPEED_HIGH &&
>>>>    	    (usb_endpoint_xfer_bulk(dep->endpoint.desc) ||
>>>> -	     usb_endpoint_xfer_isoc(dep->endpoint.desc)) && DWC3_IP_IS(DWC31))
>>>> -		num_fifos = dwc->tx_fifo_resize_max_num;
>>>> +	     usb_endpoint_xfer_isoc(dep->endpoint.desc)))
>>>> +		num_fifos = min_t(unsigned int,
>>>> +				  dep->endpoint.maxburst,
>>> maxburst can be 0 right?
>> At composite layer we are incrementing maxburst by 1 so while allocating
>> fifo maxburst can be as minimum as 1,
>> which is required and can be changed anytime with exposed configfs
>> attribute.
> Ok.
>
>>>> +				  dwc->tx_fifo_resize_max_num);
>>>>    	/* FIFO size for a single buffer */
>>>>    	fifo = dwc3_gadget_calc_tx_fifo_size(dwc, 1);
>>>> -- 
>>>> 2.17.1
Thanks,
Akash

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