vc4: HDMI Sink doesn't support RGB, something's wrong.

[Stefan Wahren]

Hi Dave,

Am 25.10.24 um 16:38 schrieb Dave Stevenson:
> Hi Stefan
>
> On Fri, 25 Oct 2024 at 14:36, Stefan Wahren <wahrenst at gmx.net> wrote:
...
> Based on that log I think your force_turbo=1 is a red-herring, or at
> least needs further investigation.
>
> Is this on a 3B, or 3B+?
Definitely a 3B+ from the year 2017 (mainline devicetree)
>
> Snippets from your log as we resume:
>
> [  216.797764] PM: suspend exit
> [  216.800473] lan78xx 1-1.1.1:1.0 eth0: Link is Down
AFAIK only the 3B+ has a Microchip LAN7800
> [  216.804503] vc4-drm soc:gpu:
> [drm:drm_helper_probe_single_connector_modes] [CONNECTOR:33:HDMI-A-1]
> [  216.804584] vc4-drm soc:gpu:
> [drm:drm_helper_probe_single_connector_modes] [CONNECTOR:33:HDMI-A-1]
> status updated from connected to disconnected
> [  216.804648] vc4-drm soc:gpu:
> [drm:drm_helper_probe_single_connector_modes] [CONNECTOR:33:HDMI-A-1]
> disconnected
> - So hotplug has signalled disconnected
> ...
> [  216.816990] vc4-drm soc:gpu: [drm:drm_mode_setcrtc] [CONNECTOR:33:HDMI-A-1]
> [  216.817079] vc4-drm soc:gpu:
> [drm:drm_atomic_helper_connector_hdmi_check] Trying with a 8 bpc
> output
> [  216.817107] vc4-drm soc:gpu:
> [drm:drm_atomic_helper_connector_hdmi_check] Trying RGB output format
> [  216.817166] vc4-drm soc:gpu:
> [drm:drm_atomic_helper_connector_hdmi_check] RGB Format, checking the
> constraints.
> [  216.817186] vc4-drm soc:gpu: [drm] HDMI Sink doesn't support RGB,
> something's wrong.
> - This is correct as the output is disconnected
> ...
> [  227.075847] vc4-drm soc:gpu: [drm:update_display_info.part.0]
> [CONNECTOR:33:HDMI-A-1] HDMI: DVI dual 0, max TMDS clock 0 kHz
> [  227.075912] vc4-drm soc:gpu: [drm:update_display_info.part.0]
> [CONNECTOR:33:HDMI-A-1] ELD monitor HP ZR2440w
> [  227.075942] vc4-drm soc:gpu: [drm:update_display_info.part.0]
> [CONNECTOR:33:HDMI-A-1] HDMI: latency present 0 0, video latency 0 0,
> audio latency 0 0
> [  227.075971] vc4-drm soc:gpu: [drm:update_display_info.part.0]
> [CONNECTOR:33:HDMI-A-1] ELD size 36, SAD count 1
> [  227.076014] vc4-drm soc:gpu: [drm:output_poll_execute]
> [CONNECTOR:33:HDMI-A-1] status updated from disconnected to connected
> [  227.076040] vc4-drm soc:gpu: [drm:output_poll_execute]
> [CONNECTOR:33:HDMI-A-1] epoch counter 3 -> 4
> [  227.076072] vc4-drm soc:gpu: [drm:drm_sysfs_hotplug_event]
> generating hotplug event
> [  227.076170] vc4-drm soc:gpu: [drm:drm_client_dev_hotplug] fbdev: ret=0
> - We now get a connect again.
>
> The 10 second interval is why I'm suspecting you're on a 3B - we have
> no interrupts for the GPIO used there (expgpio 4), whereas we do on
> 3B+ (gpio 28). The poll period is 10seconds in the absence of
> interrupts.
gpiochip0 - 54 lines:
     line   0:     "ID_SDA"       unused   input  active-high
     line   1:     "ID_SCL"       unused   input  active-high
     line   2:       "SDA1"       unused   input  active-high
     line   3:       "SCL1"       unused   input  active-high
...
     line  27:     "GPIO27"       unused   input  active-high
     line  28: "HDMI_HPD_N"        "hpd"   input   active-low [used]
     line  29: "STATUS_LED_G" "ACT" output active-high [used]
     line  30:       "CTS0"       unused   input  active-high


Sorry, I missed a possible important information. The Raspberry Pi 3B+
is not directly connected to the display. There is a passive Logilink
HDMI switch in between.
> On that suspend you were suspended for 16 seconds. Previous suspends
> were for 9 and 12 seconds.
I waited 20 seconds multiple times with and without force_hdmi and
wasn't able to reproduce it more reliable. But I agree this not a prove.

Maybe this is caused by the HDMI switch. At the end this is not
critical. My only concern was that this is an in suspend/resume handling.

I will try need to investigate this ...Thanks for your help. Stefan
> I suspect your monitor goes to sleep at around 15 seconds and is doing
> things to hotplug at that point.
> We've seen it on a couple of monitors here, and with Wayfire or labwc
> it can wake the display back up again. We haven't come up with a good
> solution to that one yet other than just ignoring hotplug.
>
>    Dave