[PATCH] usb: dwc3: gadget: Give some time to schedule isoc

[PATCH] usb: dwc3: gadget: Give some time to schedule isoc

[Thinh Nguyen]

Currently the driver will schedule isoc transfers immediately on the
next interval, which is quite aggressive when the interval is 125us.
There's report that some platforms may need more time to process the
transfer, otherwise the controller may miss the first interval. Let's
keep it simple and give the controller at least 500us to schedule the
isoc transfer.

Link: https://lore.kernel.org/linux-usb/20220302143539.GI11577@pengutronix.de/
Signed-off-by: Thinh Nguyen <Thinh.Nguyen@synopsys.com>
---
 drivers/usb/dwc3/gadget.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
index a0c883f19a41..eb88ef5dd16f 100644
--- a/drivers/usb/dwc3/gadget.c
+++ b/drivers/usb/dwc3/gadget.c
@@ -1830,7 +1830,13 @@ static int __dwc3_gadget_start_isoc(struct dwc3_ep *dep)
 	}
 
 	for (i = 0; i < DWC3_ISOC_MAX_RETRIES; i++) {
-		dep->frame_number = DWC3_ALIGN_FRAME(dep, i + 1);
+		int future_interval = i + 1;
+
+		/* Give the controller at least 500us to schedule transfers */
+		if (desc->bInterval < 3)
+			future_interval += 3 - desc->bInterval;
+
+		dep->frame_number = DWC3_ALIGN_FRAME(dep, future_interval);
 
 		ret = __dwc3_gadget_kick_transfer(dep);
 		if (ret != -EAGAIN)

base-commit: 98d107b84614a1c6b0b8009feae49c5fb0ef4758
-- 
2.28.0

Re: [PATCH] usb: dwc3: gadget: Give some time to schedule isoc

[Michael Grzeschik]

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On Mon, Mar 07, 2022 at 06:59:56PM -0800, Thinh Nguyen wrote:
>Currently the driver will schedule isoc transfers immediately on the
>next interval, which is quite aggressive when the interval is 125us.
>There's report that some platforms may need more time to process the
>transfer, otherwise the controller may miss the first interval. Let's
>keep it simple and give the controller at least 500us to schedule the
>isoc transfer.
>
>Link: https://lore.kernel.org/linux-usb/20220302143539.GI11577@pengutronix.de/
>Signed-off-by: Thinh Nguyen <Thinh.Nguyen@synopsys.com>

Tested-by: Michael Grzeschik <m.grzeschik@pengutronix.de>

>---
> drivers/usb/dwc3/gadget.c | 8 +++++++-
> 1 file changed, 7 insertions(+), 1 deletion(-)
>
>diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
>index a0c883f19a41..eb88ef5dd16f 100644
>--- a/drivers/usb/dwc3/gadget.c
>+++ b/drivers/usb/dwc3/gadget.c
>@@ -1830,7 +1830,13 @@ static int __dwc3_gadget_start_isoc(struct dwc3_ep *dep)
> 	}
>
> 	for (i = 0; i < DWC3_ISOC_MAX_RETRIES; i++) {
>-		dep->frame_number = DWC3_ALIGN_FRAME(dep, i + 1);
>+		int future_interval = i + 1;
>+
>+		/* Give the controller at least 500us to schedule transfers */
>+		if (desc->bInterval < 3)
>+			future_interval += 3 - desc->bInterval;
>+
>+		dep->frame_number = DWC3_ALIGN_FRAME(dep, future_interval);
>
> 		ret = __dwc3_gadget_kick_transfer(dep);
> 		if (ret != -EAGAIN)
>
>base-commit: 98d107b84614a1c6b0b8009feae49c5fb0ef4758
>-- 
>2.28.0
>
>

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