Re: [PATCH 1/2] drm/vc4: kms: Assign a FIFO to enabled CRTCs instead of active

[Maxime Ripard <maxime@cerno.tech>]

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On Thu, Sep 24, 2020 at 05:08:56PM +0900, Hoegeun Kwon wrote:
> Hi Maxime,
> 
> On 9/18/20 11:59 PM, Maxime Ripard wrote:
> > The HVS has three FIFOs that can be assigned to a number of PixelValves
> > through a mux.
> >
> > However, changing that FIFO requires that we disable and then enable the
> > pixelvalve, so we want to assign FIFOs to all the enabled CRTCs, and not
> > just the active ones.
> 
> Thanks for the patch.
> 
> There is a problem when doing page flip.
> After connecting 2 HDMIs without hotplug and booting.(Same thing when
> using hotplug.)
> 
> When executing page flip for each of HDMI 0 and 1 in modetest
> operation does not work normally. (crtc irq does not occur, so timeout 
> occurs.)
> Sometimes both hdmi 0 or 1 work or not.
> 
> LOGs:
> root:~> modetest -Mvc4 -s 32:1280x720 -v
> setting mode 1280x720-60Hz@XR24 on connectors 32, crtc 64
> failed to set gamma: Invalid argument
> freq: 60.24Hz
> freq: 60.00Hz
> 
> root:~> modetest -Mvc4 -s 38:1280x720 -v
> setting mode 1280x720-60Hz@XR24 on connectors 38, crtc 69
> failed to set gamma: Invalid argument
> select timed out or error (ret 0)
> select timed out or error (ret 0)
> 
> Could you please check it?

So I can reproduce that bug, but I've not been able to fix it yet.

The issue seems to happen 100% of the time when you start first with the
second connector, and then the first. It creates yet another muxing
corner case, which is that when the first modeset runs, there's only one
enabled CRTC (with the 69 here) that gets assigned the channel 0 (since
it's the only one and it can run from that channel). However, when
modeset exits, it doesn't disable that CRTC for some reason.

Then you enable a second CRTC (64) with the second modeset command, but
it has a lower index so it gets evaluated first and gets assigned the
channel 0 as well since we haven't removed the CRTC 69 from the pool
yet.

I've fixed that up by first removing the channels in current use, and
then allocating them in two separate passes, but it doesn't address the
problem entirely, so I'll keep looking.

Maxime

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