linux-kernel - Re: [PATCH v2] usb: dwc3: gadget: Refine the logic for resizing Tx FIFOs

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Message-ID: <20240905211817.jzbjlfrysql37cqu@synopsys.com>
Date: Thu, 5 Sep 2024 21:18:22 +0000
From: Thinh Nguyen <Thinh.Nguyen@...opsys.com>
To: AKASH KUMAR <quic_akakum@...cinc.com>
CC: Thinh Nguyen <Thinh.Nguyen@...opsys.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jing Leng <jleng@...arella.com>, 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 v2] usb: dwc3: gadget: Refine the logic for resizing Tx
 FIFOs

On Thu, Sep 05, 2024, AKASH KUMAR wrote:
> Hi Thinh,
> 
> On 9/5/2024 3:36 AM, Thinh Nguyen wrote:
> > On Wed, Sep 04, 2024, AKASH KUMAR wrote:
> > > Hi Thinh,
> > > 
> > > On 9/4/2024 3:41 AM, Thinh Nguyen wrote:
> > > > On Tue, Sep 03, 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.
> > > > > 
> > > > > Isochronous Transfers: Ensures that num_fifos is sufficient by
> > > > > considering the maxburst value and the maximum packet multiplier.
> > > > > 
> > > > > 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 endpoint’s maxburst and maxpacket.
> > > > > 
> > > > > Signed-off-by: Akash Kumar <quic_akakum@...cinc.com>
> > > > > ---
> > > > > Changes for v2:
> > > > > Redefine logic for resizing tx fifos.
> > > > > 
> > > > > 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 | 15 ++++++---------
> > > > >    1 file changed, 6 insertions(+), 9 deletions(-)
> > > > > 
> > > > > diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
> > > > > index 89fc690fdf34..49809a931104 100644
> > > > > --- a/drivers/usb/dwc3/gadget.c
> > > > > +++ b/drivers/usb/dwc3/gadget.c
> > > > > @@ -778,15 +778,12 @@ 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 (dep->endpoint.maxburst > 6 &&
> > > > > -	    (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;
> > > > > +	if (usb_endpoint_xfer_bulk(dep->endpoint.desc))
> > > > > +		num_fifos = min_t(unsigned int, dep->endpoint.maxburst + 1,
> > > > > +				  dwc->tx_fifo_resize_max_num);
> > > > > +	if (usb_endpoint_xfer_isoc(dep->endpoint.desc))
> > > > > +		num_fifos = max_t(unsigned int, dep->endpoint.maxburst,
> > > > > +				  usb_endpoint_maxp_mult(dep->endpoint.desc));
> > > > No. Don't mix usb_endpoint_maxp_mult with maxburst like this. Check base
> > > > on operating speed. Also, now you're ignoring tx_fifo_resize_max_num for
> > > > isoc.
> > > Sure will add separate check based on speed.
> > > 
> > > We have to support three versions of CAM support through same dt and image
> > > SS/SS+ capable cam which needs 10k fifo
> > > HS cams which needs 3K
> > > multi UVC cams which needs 1k and 2k fifo
> > > 
> > > Putting any dependency with tx_fifo_resize_max_num, we can't achieve 1k and
> > > 10K,
> > That doesn't make sense. The tx_fifo_resize_max_num is a configurable
> > constraint through devicetree property. How can it not work?
> i have tested and i don't have any problem in adding constraint with HS but
> for SS
> i need to set fifo size of 1K for 1 cam and 10k for other.
> if i add any boundary with tx_fifo_resize_max_num (either max or min ) one
> of tx fifo size
> either 1k or 10K i won't be able to set. So i request you allow to for >=SS
> , to decide fifo
> size based on maxburst only. i will be pusing patchset3 with that. please
> approve consideration this.

I still don't understand. Did you try to increase the
tx_fifo_resize_max_num via devicetree property?

I don't want inconsistent behavior where tx_fifo_resize_max_num applies
to some but not others.

BR,
Thinh