On 3/27/2025 3:04 PM, Michał Pecio wrote:
On Thu, 27 Mar 2025 12:08:53 +0530, Rangoju, Raju wrote:
What if there is an ISOC IN endpoint with 64ms ESIT? I haven't yet seen such a slow isoc endpoint, but I think they are allowed by the spec. Your changelog suggests any periodic IN endpoint can trigger this bug.
If such an endpoint is implemented, it could theoretically contribute to scheduling conflicts similar to those caused by INT endpoints in this context. However, our observations and testing on affected platforms primarily involved periodic IN endpoints with service intervals greater than 32ms interfering with ISOC OUT endpoints.
In such case it would make sense to drop the check for usb_endpoint_xfer_int(&ep->desc) and rely on existing (xfer_int || xfer_isoc) in the outer 'if'.
Got it. I'll address this in subsequent patch.
I'm not completely sure about this corner case if HS OUT endpoints can inadvertently get affected when co-existing with long-interval LS/FS IN endpoints. Our IP vendor confirmed that LS/FS devices are not affected.
There is also a third case of a FS device behind an external HS hub. The device will look like FS to this code here, but the xHC will need to schedule HS transactions to service it.
In that case, the original code I provided in this patch doesn't include a check for 'udev->speed' and is applicable to FS devices as well. I think this code should remain unchanged to properly address the third scenario you mentioned.
Regards, Michal