vc4: Couldn't stop firmware display driver during boot

[Stefan Wahren]

Hi Maxime,

Am 11.04.22 um 09:35 schrieb Maxime Ripard:
> Hi Stefan,
>
> On Sun, Apr 10, 2022 at 02:32:02AM +0200, Stefan Wahren wrote:
>> Am 09.04.22 um 21:25 schrieb Stefan Wahren:
>>> Hi,
>>>
>>> today i tested Linux 5.18-rc1 on my Raspberry Pi 400 connected to my
>>> HDMI display (multi_v7_defconfig + CONFIG_ARM_LPAE, firmware:
>>> 2021-01-08T14:31:16) and i'm getting these strange errors from
>>> raspberrypi-firmware driver / vc4 during boot:
>>>
>>> [   13.094733] fb0: switching to vc4 from simple
>>> [   13.110759] Console: switching to colour dummy device 80x30
>>> [   13.120691] raspberrypi-firmware soc:firmware: Request 0x00030066
>>> returned status 0x80000001
>>> [   13.120715] vc4-drm gpu: [drm] Couldn't stop firmware display driver:
>>> -22
>> This is a new error which was introduced with Linux 5.18-rc1 (c406ad5e4a85
>> "drm/vc4: Notify the firmware when DRM is in charge"). 0x00030066 stands for
>> the new firmware property RPI_FIRMWARE_NOTIFY_DISPLAY_DONE. And i guess the
>> firmware from January 2021 doesn't support it?
> If I remember well, this was added some time in the middle of last year,
> so it wouldn't surprise me that your firmware doesn't support it.
>
> It's not really harmful, but it might still be a good idea to upgrade
> your firmware. The display pipeline has an unflushable FIFO between
> devices and if we don't take special care when disabling all the devices
> in that pipeline, we end up with a shift of one pixel for the rest of
> the system's life.
>
> We have some code to deal with the transition between the firmware and
> the kernel, but we couldn't make it work reliably so we ended up asking
> the firmware instead.
>
> So.. Yeah, it's bad if you want to use the displays output, but it not
> critical either.

I understand. I think it would be nice to give the user a more helpful 
warning how to possible fix this, because we cannot assume that every 
system has the latest firmware.

Also i'm not sure if should give this warning once or on every probing 
attempt.

Best regards
Stefan

>
> Maxime