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Bug#925334: vc4: CMA fills up and screen not updated anymore on raspi3


* Romain Perier (Wed, 27 Mar 2019 21:33:19 +0100):
> Return-Path: <romain.perier@gmail.com>
> Message-ID: <20190327203319.GA15993@debby.home>
> From: Romain Perier <romain.perier@gmail.com>
> Subject: Re: Bug#925334: vc4: CMA fills up and screen not updated anymore
>  on raspi3
> To: Fabian Pietsch <fabian-debian@canvon.de>, 925334@bugs.debian.org
> User-Agent: Mutt/1.10.1 (2018-07-13)
> On Wed, Mar 27, 2019 at 03:29:21PM +0100, Fabian Pietsch wrote:


> > the bug is still present in the current version. It took a freshly
> > booted, idle system 3304 seconds for the bug to occur, though,
> > so this time rather an hour (than 10-30min as stated before).


> > So vc4_v3d which reported the error seems to be in status=error
> > and counts as suspended. Manual attempts to get it to resume again,
> > now that more cma is free again, failed, but there are probably ways
> > I don't know about.


> Could you test, two stuffs for me ? :
> 1. The VC4 driver seems to use runtime pm operations, could you try to
> disable runtime suspend completly (there are kernel parameters for this
> if I remember correctly) ?

Didn't find anything useful to that regard in linux-doc Documentation/
and by googling. Could you please tell me how?

> 2. Your kernel cmdline are... weird, could you try with minimalistic
> kernel cmdline ? Only keep console= for logging to uart and/or to your
> tty0 and keep your rootfs.

The initial part until the two spaces seems to be auto-generated by the
firmware at boot, so I guess I can't change or suppress it; if it should
be possible, again, please tell me how.

My kernel cmdline as passed *to* the firmware is:

| fabian@rpi3:~$ cat /boot/firmware/cmdline.txt
| console=tty0 console=ttyS1,115200 root=/dev/mmcblk0p2 rw elevator=deadline fsck.repair=yes net.ifnames=0 cma=128M rootwait

This is just auto-generated by the raspi3-firmware package to which
you (Romain Perier) seem to be contributing.

As suggested, I tested more compact cmdline.txt, though:

| root=/dev/mmcblk0p2

| console=tty0 root=/dev/mmcblk0p2

| console=tty0 root=/dev/mmcblk0p2 cma=128M

With the first two, cma defaulted to 64M and already the lightdm login
screen stops updating after a few seconds to minutes. With the 3rd,
the bug initially didn't happen so I used X a bit, then logged out and
let the system fall idle; the bug then seems to have happened
9868 seconds after boot (according to dmesg --follow).

Regards, Fabian

Fabian "canvon" Pietsch - https://www.canvon.de/

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