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 updated logic is more flexible and specifically designed to meet
the unique requirements of both bulk and isochronous transfers. We
have made every effort to satisfy all needs and requirements, but
please note that this has only been verified on our specific platform
and application.

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
endpoint’s maxburst and maxpacket.

Signed-off-by: Akash Kumar <quic_akakum@quicinc.com>
---
Changes for v4:
Updated commit message as per review comments to clarify that it
has been tested on specific platforms only and tried best to
match all expectations.

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,
+				  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,
+				  dwc->tx_fifo_resize_max_num);
 
 	/* FIFO size for a single buffer */
 	fifo = dwc3_gadget_calc_tx_fifo_size(dwc, 1);
-- 
2.17.1