Messages in this thread | | | Subject | Re: [PATCH v5 00/39] i.MX Media Driver | From | Steve Longerbeam <> | Date | Sun, 12 Mar 2017 13:16:02 -0700 |
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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.
Steve
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