usb_hub: split powered state and request to prevent glitches #21
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Emantor
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Jun 7, 2023
Previously a change request could come in while the polling task was reading the status resulting in the state switching back and forth. Signed-off-by: Leonard Göhrs <l.goehrs@pengutronix.de>
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The power state of the USB Hub ports may be changed by the
tacdor by some other program, e.g.uhubctl.We do not (yet) have an interface to be notified of changes to the port, so we use periodic polling instead.
Up until now we've just accepted that a
topic.set()triggered by the periodic polling triggers a write to the port with the state it just read.This does however result in glitches when a new value is set e.g. via the API while the polling task is reading the current state, resulting in the state being reset to the previous state.
This issue is triggered by the scripts used to stress the TAC during an EMI test.
Related Pull Requests
screens/usb.rsthat would otherwise introduce conflicts. Which is why it should be merged first.