Re: [PATCH] usb: dwc3: gadget: Fix TX FIFO size for HS ISOC endpoints

From: AKASH KUMAR
Date: Wed Aug 28 2024 - 00:11:38 EST


Hi Thinh,

On 8/28/2024 4:45 AM, Thinh Nguyen wrote:
On Tue, Aug 27, 2024, Akash Kumar wrote:
Use 2K TX FIFO size for low-resolution UVC cameras to support the
maximum possible UVC instances. Restrict 2K TX FIFO size based on
the minimum maxburst required to run low-resolution UVC cameras.

Signed-off-by: Akash Kumar <quic_akakum@xxxxxxxxxxx>
---
drivers/usb/dwc3/gadget.c | 4 ++++
1 file changed, 4 insertions(+)

diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
index 89fc690fdf34..f342ccda6705 100644
--- a/drivers/usb/dwc3/gadget.c
+++ b/drivers/usb/dwc3/gadget.c
@@ -788,6 +788,10 @@ static int dwc3_gadget_resize_tx_fifos(struct dwc3_ep *dep)
usb_endpoint_xfer_isoc(dep->endpoint.desc)) && DWC3_IP_IS(DWC31))
num_fifos = dwc->tx_fifo_resize_max_num;
+ if (dep->endpoint.maxburst <= 1 &&
+ usb_endpoint_xfer_isoc(dep->endpoint.desc))
+ num_fifos = 2;
+
/* FIFO size for a single buffer */
fifo = dwc3_gadget_calc_tx_fifo_size(dwc, 1);
--
2.17.1

These settings are starting to get too specific for each application.
Can we find a better calculation?

Perhaps something like this? (code not tested)

diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
index 9a18973ebc05..d54b08f92aea 100644
--- a/drivers/usb/dwc3/gadget.c
+++ b/drivers/usb/dwc3/gadget.c
@@ -908,15 +908,10 @@ 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)) ||
+ if (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;
+ num_fifos = min_t(unsigned int, dep->endpoint.maxburst + 1,
+ dwc->tx_fifo_resize_max_num);
/* FIFO size for a single buffer */
fifo = dwc3_gadget_calc_tx_fifo_size(dwc, 1);

should be fine for me, as earlier there was no case handling for maxburst <= 1, by allocating fifo based on maxburst itself

should be a good solution and will work for all as they customize based on maxburst through init scripts, let me test and update.

Thanks,
Akash