Messages in this thread | | | Subject | Re: [PATCH v5 00/39] i.MX Media Driver | From | Steve Longerbeam <> | Date | Sun, 12 Mar 2017 13:36:32 -0700 |
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On 03/12/2017 01:16 PM, Steve Longerbeam wrote: > > > On 03/12/2017 12:44 PM, Steve Longerbeam wrote: >> >> >> On 03/12/2017 12:29 PM, Russell King - ARM Linux wrote: >>> On Sun, Mar 12, 2017 at 12:21:45PM -0700, Steve Longerbeam wrote: >>>> There's actually nothing preventing userland from disabling a link >>>> multiple times, and imx_media_link_notify() complies, and so >>>> csi_s_power(OFF) gets called multiple times, and so that WARN_ON() >>>> in there is silly, I borrowed this from other MC driver examples, >>>> but it makes no sense to me, I'll remove it and prevent the power >>>> count from going negative. >>> >>> Hmm. So what happens if one of the CSI's links is enabled, and we >>> disable a different link from the CSI several times? Doesn't that >>> mean the power count will go to zero despite there being an enabled >>> link? >> >> Yes, the CSI will be powered off even if it still has an enabled link. >> But one of its other links has been disabled, meaning the pipeline as >> a whole is disabled. So I think it makes sense to power down the CSI, >> the pipeline isn't usable at that point. >> >> And remember that the CSI does not allow both output pads to be enabled >> at the same time. If that were so then indeed there would be a problem, >> because it would mean there is another active pipeline that requires the >> CSI being powered on, but that's not the case. >> >> I think this is consistent with the other entities as well, but I will >> double check. > > > At first I thought this could be a problem for one entity, the csi-2 > receiver. > > It can enable all four of its output pads at once (if the input stream > contains all 4 virtual channels, the csi-2 receiver must support > demuxing all of them onto all 4 of its output pads). > > But after more review, this should not be an issue. If a csi-2 sink > (a CSI or a CSI mux) link is disabled, the csi-2 receiver is no longer > reachable from that sink, so attempts to disable the csi-2 via that > path again is not possible. The other potential problem is disabling > from the csi-2's own sink pad, but in that case the csi-2 no longer > has a source, so again it makes sense to power off the csi-2 even > if it has enabled output pads. >
But hold on, if my logic is correct, then why did the CSI power-off get reached in your case, multiple times? Yes I think there is a bug, link_notify() is not checking if the link has already been disabled. I will fix this. But I'm surprised media core's link_notify handling doesn't do this.
Steve
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