usb: dwc3: gadget: Refine the logic for resizing Tx FIFOs

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, verified
on our specific platform and application.

Bulk Transfers: Ensures that num_fifos is optimized by considering both
the maxburst and DT property "tx-fifo-max-num" for super speed and
above. For high-speed and below bulk endpoints, a 2K TxFIFO allocation
is used to meet efficient data transfer needs, considering
FIFO-constrained platforms.

Isochronous Transfers: Ensures that num_fifos is sufficient by
considering the maximum packet multiplier for HS and below and maxburst
for Super-speed and above eps, along with a constraint with the DT
property "tx-fifo-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. This structured approach ensures that the appropriate number
of FIFOs is allocated based on the endpoint type and USB speed.

Signed-off-by: Akash Kumar <quic_akakum@quicinc.com>
Acked-by: Thinh Nguyen <Thinh.Nguyen@synopsys.com>
Link: https://lore.kernel.org/r/20241017064423.7056-1-quic_akakum@quicinc.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 24 insertions, 9 deletions

diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
index 4959c26d3b71..2fed2aa01407 100644
--- a/drivers/usb/dwc3/gadget.c
+++ b/drivers/usb/dwc3/gadget.c
@@ -775,15 +775,30 @@ 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;
+	switch (dwc->gadget->speed) {
+	case USB_SPEED_SUPER_PLUS:
+	case USB_SPEED_SUPER:
+		if (usb_endpoint_xfer_bulk(dep->endpoint.desc) ||
+		    usb_endpoint_xfer_isoc(dep->endpoint.desc))
+			num_fifos = min_t(unsigned int,
+					  dep->endpoint.maxburst,
+					  dwc->tx_fifo_resize_max_num);
+		break;
+	case USB_SPEED_HIGH:
+		if (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);
+			break;
+		}
+		fallthrough;
+	case USB_SPEED_FULL:
+		if (usb_endpoint_xfer_bulk(dep->endpoint.desc))
+			num_fifos = 2;
+		break;
+	default:
+		break;
+	}
 
 	/* FIFO size for a single buffer */
 	fifo = dwc3_gadget_calc_tx_fifo_size(dwc, 1);