Fix for #4685 #4755
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Fix for #4685 #4755
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Don't calculate space based on the number of TRBs in the current segment, as it's OK to wrap to the start (and flip the cycle state bit). Signed-off-by: Jonathan Bell <[email protected]>
…lers Certain transfer ring access patterns can cause the controller to hang fetching TRBs for a USB2.0 endpoint. - If two USB2.0 endpoints are active at once and - Both endpoints are traversing a Link TRB where the following segment has a lower page address and - One of the endpoints is a Bulk IN and - The other endpoint is an Interrupt IN Then the Interrupt IN endpoint can end up not getting polled. It is unclear what the precise failure mode is, as the controller seems to haphazardly and repeatedly fetch TRBs for both endpoints but does not advance the Interrupt endpoint transfer. As a workaround, add a quirk that initially constrains all USB2.0 transfer rings to a single segment in size. If for any reason a device driver queues up enough outstanding transfers to fill the ring segment, then the ring will be expanded. This has not been seen to occur with UMS or UVC drivers, which aggressively queue buffers. Signed-off-by: Jonathan Bell <[email protected]>
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See: raspberrypi/linux#4755 kernel: DPI panel configuration See: raspberrypi/linux#4753 kernel: KMS 7" DSI panel and touchscreen fixes See: raspberrypi/linux#4750 kernel: drm/vc4: Hold pm_runtime for vc4 See: raspberrypi/linux#4706
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See: raspberrypi/linux#4755 kernel: DPI panel configuration See: raspberrypi/linux#4753 kernel: KMS 7" DSI panel and touchscreen fixes See: raspberrypi/linux#4750 kernel: drm/vc4: Hold pm_runtime for vc4 See: raspberrypi/linux#4706
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I don't have exactly the same hardware setup as the linked issue, but my equivalent testcase (Asix dongle with a modified interrupt endpoint interval) no longer fails with this patch applied.
While the failure was only seen when a bulk IN and interrupt IN endpoint were both active, there's no proof that the same thing can't occur with combinations of bulk IN and some other periodic endpoint type, so applying the segment restriction globally hedges against other random breakages.