Thinh Nguyen wrote:

Hi,

Felipe Balbi wrote:

quoted

Hi,

Thinh Nguyen [off-list ref] writes:

quoted

quoted

quoted

@@ -3863,7 +3868,7 @@ int dwc3_gadget_init(struct dwc3 *dwc)
 	 * sure we're starting from a well known location.
 	 */
 
-	ret = dwc3_gadget_init_endpoints(dwc, dwc->num_eps);
+	ret = dwc3_gadget_init_endpoints(dwc);
 	if (ret)
 		goto err4;

heh, looking at original commit, we used to have num_in_eps and
num_out_eps. In fact, this commit will reintroduce another problem that
Bryan tried to solve. num_eps - num_in_eps is not necessarily
num_out_eps.

From my understanding, that's not what Bryan's saying. Here's the
snippet of the commit message:

"
    It's possible to configure RTL such that DWC_USB3_NUM_EPS is equal to
    DWC_USB3_NUM_IN_EPS.

    dwc3-core calculates the number of OUT endpoints as DWC_USB3_NUM minus
    DWC_USB3_NUM_IN_EPS. If RTL has been configured with DWC_USB3_NUM_IN_EPS
    equal to DWC_USB3_NUM then dwc3-core will calculate the number of OUT
    endpoints as zero.

    For example a from dwc3_core_num_eps() shows:
    [    1.565000]  /usb0@f01d0000: found 8 IN and 0 OUT endpoints
"

He just stated that you can configure to have num_eps equals to
num_in_eps. Basically it means there's no OUT physical endpoint. Not

no, that's not what it means. I don't have access to DWC3 documentation
anymore, but from what I remember every physical endpoint _can_ be
configured as bidirectional. In other words, DWC3_USB3_NUM_EPS ==
DWC3_USB3_NUM_IN_EPS could mean that every endpoint in the system is
bidirectional.

quoted

sure why you would ever want to do that because that will prevent any
device from working. The reason we have DWC_USB3x_NUM_IN_EPS and
DWC_USB3x_NUM_EPS exposed in the global HW param so that the driver know
how many endpoints are available for each direction. If for some reason
this mechanism fails, there's something fundamentally wrong in the HW
configuration. We have not seen this problem, and I don't think Bryan
did from his commit statement either.

Please confirm this internally. That was my original assumption too,
until Bryan pointed me to a particular section of the
specification. Unfortunately it's far too long ago and I can't even
verify documentation :-)

quoted

quoted

How have you verified this patch? Did you read Bryan's commit log? This
is likely to reintroduce the problem raised by Bryan.

We verified with our FPGA HAPS with various number of endpoints. No
issue is seen.

That's cool. Could you please make sure our understanding of this is
sound and won't interfere with any designs? If we modify this part of
the code again, I'd like to see a clear reference to a specific section
of the databook detailing the expected behavior :-)

cheers

Hm... I didn't consider bidirection endpoint other than control endpoint.

DWC3_USB3x_NUM_EPS specifies the number of device mode for single
directional endpoints. A bidirectional endpoint needs 2 single
directional endpoints, 1 IN and 1 OUT. So, if your setup uses 3
bidirection endpoints and only those, DWC3_USB3x_NUM_EPS should be 6.
DWC3_USB3x_NUM_IN_EPS specifies the maximum number of IN endpoint active
at any time.

However, I will have to double check and confirm internally regarding
how to determine many endpoint would be available if bidirection
endpoints come into play.

Thanks for pointing this out. Will get back on this.

Thinh

Ok. Just had some discussion internally. So, like you said, any endpoint
can be configured in either direction. However, we are limited to
configuring up to DWC_USB3x_NUM_IN_EPS because each IN endpoint has its
own TxFIFO while for OUT, they share the same RxFIFO. So we could have
up to DWC_USB3x_NUM_EPS number of OUT endpoints. So, the issue Bryan
attempted to address is still there.

However, the current code still has some assumption on the number of IN
and OUT endpoints, I need to think of a better solution.

Thanks,
Thinh