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

[AKASH KUMAR]

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@xxxxxxxxxxx>
> > > > ---
> > > > 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.
> > it has to be decided by maxbursts itself which user can configure.
> > All uvc gadget applications supports configurable maxburst which they use
> > while opening,
> > so it should be better for isoc eps to decide fifo based on maxbursts.
> We should not just look at maxburst. It's only applicable to usb3
> speeds. How the function driver configures maxp_mult* vs maxbursts is
> independent. So let's keep the check separate base on speed for isoc.
>
> Thanks,
> Thinh
>
> [*] Let's refer the mouthful "additional transaction opportunities" as
> maxp_mult.

yes of course i will add separate check for maxp_mult in patchset3 for 
<=HS speed devices.

Thanks,
Akash