linux-kernel - Re: [PATCH v14 3/6] usb: dwc3: Resize TX FIFOs to meet EP bursting requirements

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Date:   Wed, 14 Jul 2021 02:58:41 +0000
From:   Thinh Nguyen <Thinh.Nguyen@...opsys.com>
To:     Felipe Balbi <balbi@...nel.org>,
        Thinh Nguyen <Thinh.Nguyen@...opsys.com>,
        Wesley Cheng <wcheng@...eaurora.org>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "agross@...nel.org" <agross@...nel.org>,
        "bjorn.andersson@...aro.org" <bjorn.andersson@...aro.org>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "frowand.list@...il.com" <frowand.list@...il.com>
CC:     "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-arm-msm@...r.kernel.org" <linux-arm-msm@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "jackp@...eaurora.org" <jackp@...eaurora.org>
Subject: Re: [PATCH v14 3/6] usb: dwc3: Resize TX FIFOs to meet EP bursting
 requirements

Felipe Balbi wrote:
> 
> Hi,
> 
> Thinh Nguyen <Thinh.Nguyen@...opsys.com> writes:
>> Wesley Cheng wrote:
>>> Some devices have USB compositions which may require multiple endpoints
>>> that support EP bursting.  HW defined TX FIFO sizes may not always be
>>> sufficient for these compositions.  By utilizing flexible TX FIFO
>>> allocation, this allows for endpoints to request the required FIFO depth to
>>> achieve higher bandwidth.  With some higher bMaxBurst configurations, using
>>> a larger TX FIFO size results in better TX throughput.
>>>
>>> By introducing the check_config() callback, the resizing logic can fetch
>>> the maximum number of endpoints used in the USB composition (can contain
>>> multiple configurations), which helps ensure that the resizing logic can
>>> fulfill the configuration(s), or return an error to the gadget layer
>>> otherwise during bind time.
>>>
>>> Signed-off-by: Wesley Cheng <wcheng@...eaurora.org>
>>> ---
>>>  drivers/usb/dwc3/core.c   |  15 +++
>>>  drivers/usb/dwc3/core.h   |  16 ++++
>>>  drivers/usb/dwc3/ep0.c    |   2 +
>>>  drivers/usb/dwc3/gadget.c | 232 ++++++++++++++++++++++++++++++++++++++++++++++
>>>  4 files changed, 265 insertions(+)
>>>

<snip>

>>> +/*
>>> + * dwc3_gadget_resize_tx_fifos - reallocate fifo spaces for current use-case
>>> + * @dwc: pointer to our context structure
>>> + *
>>> + * This function will a best effort FIFO allocation in order
>>> + * to improve FIFO usage and throughput, while still allowing
>>> + * us to enable as many endpoints as possible.
>>> + *
>>> + * Keep in mind that this operation will be highly dependent
>>> + * on the configured size for RAM1 - which contains TxFifo -,
>>> + * the amount of endpoints enabled on coreConsultant tool, and
>>> + * the width of the Master Bus.
>>> + *
>>> + * In general, FIFO depths are represented with the following equation:
>>> + *
>>> + * fifo_size = mult * ((max_packet + mdwidth)/mdwidth + 1) + 1
>>> + *
>>> + * In conjunction with dwc3_gadget_check_config(), this resizing logic will
>>> + * ensure that all endpoints will have enough internal memory for one max
>>> + * packet per endpoint.
>>> + */
>>> +static int dwc3_gadget_resize_tx_fifos(struct dwc3_ep *dep)
>>> +{
>>> +	struct dwc3 *dwc = dep->dwc;
>>> +	int fifo_0_start;
>>> +	int ram1_depth;
>>> +	int fifo_size;
>>> +	int min_depth;
>>> +	int num_in_ep;
>>> +	int remaining;
>>> +	int num_fifos = 1;
>>> +	int fifo;
>>> +	int tmp;
>>> +
>>> +	if (!dwc->do_fifo_resize)
>>> +		return 0;
>>> +
>>> +	/* resize IN endpoints except ep0 */
>>> +	if (!usb_endpoint_dir_in(dep->endpoint.desc) || dep->number <= 1)
>>> +		return 0;
>>
>>> +
>>> +	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 (dep->endpoint.maxburst > 6 &&
>>> +	    usb_endpoint_xfer_bulk(dep->endpoint.desc) && DWC3_IP_IS(DWC31))
>>> +		num_fifos = dwc->tx_fifo_resize_max_num;
>>
>> Why only bulk? Isoc should be at least equal or more than bulk.
>> Also, make this applicable to DWC_usb32 also.
> 
> this should be applicable to all DWC3 versions, no? dwc3, 31 and 32.
> 

Yes.

BR,
Thinh