oldteen
Posts: 4
Joined: Sun Sep 17, 2017 8:38 am

CM3 and vc4 driver

Fri Sep 22, 2017 10:12 pm

Hello,

I have to run a small SDL2 application on a CM3. A small 800x480 screen is connected on the board.

Actually I have these lines in my config.txt:

Code: Select all

dtoverlay=dpi24
overscan_left=0
overscan_right=0
overscan_top=0
overscan_bottom=0
framebuffer_width=800
framebuffer_height=480
enable_dpi_lcd=1
display_default_lcd=1
dpi_group=2
dpi_mode=87
dpi_output_format=0x6f007
display_rotate=2
hdmi_timings=800 0 40 48 88 480 0 13 3 32 0 0 0 60 0 32000000 6
All run fine, I've got gui but my application run at 3 fps...
I've installed the vc4 driver and add this line to my config.txt : dtoverlay=vc4-kms-v3d (do it with raspi-config). Now the system don't show anything (don't see the linux verbose lines before x11 start).

Someone can confirm to me that cm3 run well with opengl enabled ?
I am not an expert. I start with raspberry stretch lite, install gui + mesa driver.

run well on a standard raspberry 3 (+200 fps)

Maybe the problem come with the mix of touch screen (800x480) and vc4 driver.

Any idea ?
Thanks,
oldteen

6by9
Raspberry Pi Engineer & Forum Moderator
Raspberry Pi Engineer & Forum Moderator
Posts: 6327
Joined: Wed Dec 04, 2013 11:27 am
Location: ZZ9 Plural Z Alpha, aka just outside Cambridge.

Re: CM3 and vc4 driver

Sat Sep 23, 2017 7:30 am

I don't recall the vc4-kms-v3d driver having any support for dpi, and DSI is only partial.
If you use the vc4-fkms-v3d (fake kms) driver instead then the displays are still driven by the firmware (which does support dpi and DSI) with the VC4 driver feeding it.
Software Engineer at Raspberry Pi Trading. Views expressed are still personal views.
I'm not interested in doing contracts for bespoke functionality - please don't ask.

oldteen
Posts: 4
Joined: Sun Sep 17, 2017 8:38 am

Re: CM3 and vc4 driver

Sat Sep 23, 2017 9:12 am

Thanks 6by9

I try now:
- with fkms I see gui and can start my SDL application
- but I've got only 3 fps :(
- with fkms driver, all run well on a pi 3 and his HDMI port

I continue to investigate

6by9
Raspberry Pi Engineer & Forum Moderator
Raspberry Pi Engineer & Forum Moderator
Posts: 6327
Joined: Wed Dec 04, 2013 11:27 am
Location: ZZ9 Plural Z Alpha, aka just outside Cambridge.

Re: CM3 and vc4 driver

Sat Sep 23, 2017 9:19 am

I claim no real expertise on the state of the VC4 and kms drivers, but it'd be worth trying fkms with hdmi to see what the refresh rate is there. Mainly to confirm if it is the display or drivers at fault.
It doesn't need to be on a cm, a normal Pi3 should be close enough.
Software Engineer at Raspberry Pi Trading. Views expressed are still personal views.
I'm not interested in doing contracts for bespoke functionality - please don't ask.

Andy1978
Posts: 16
Joined: Fri Jan 04, 2013 7:01 pm

Re: CM3 and vc4 driver

Wed Oct 31, 2018 10:32 am

As far as I understand there was a merge from Erics PR https://github.com/raspberrypi/linux/pull/2429

Does this only enable DPI for the mentioned adafruit display?
I've updated to the lastes kernel (4.14.78-v7+) and firmware (724d81b3f87eb71045e938e572eca140fb8828ab) but still have a black display

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