[Intel-gfx] Graphics on thinkpad x270 after dock/undock works only for the first time (CPU pipe B FIFO underrun)

[Rodrigo Vivi]

On Sat, Dec 30, 2017 at 12:53:58PM +0000, Jiri Kosina wrote:
> On Sat, 30 Dec 2017, Jiri Kosina wrote:
> 
> > Seems like disabling RC6 on the kernel command line works this around, and 
> > I can dock / undock several times in a row with the image always coming 
> > up properly on the external display.
> > 
> > On the first undock, the WARN_ONCE() below triggers, so I believe each 
> > undock leaks memory.
> > 
> > [   38.755084] Failed to release pages: bind_count=1, pages_pin_count=1, pin_global=0
> > [   38.755138] WARNING: CPU: 3 PID: 96 at ../drivers/gpu/drm/i915/i915_gem_userptr.c:89 cancel_userptr+0xe5/0xf0 [i915]
> 
> OK, I am seeing this warning with current Linus' tree (5aa90a845) even 
> without any attempt to dock/undock, so it's probably unrelated to external 
> outputs and it only by coincidence appeared originally at the same time I 
> docked the machine.
> 
> So there are two separate issues on this machine with latest kernel 
> (neither of them probably being regression):
> 
> - I have to disable i915 RC6 at the kernel cmdline, otherwise external 
>   (dock) display gets output only randomly (seems like always only on 
>   first dock)

Joonas, Chris, time to bring rc6_enable back on next-fixes before we
remove this support entirely?

> 
> - the warning, which triggers at not really deterministic time after boot, 
>   but usually rather quickly

Jiri, could you please report these issues separately on bugs.freedesktop.org?
Are them regressions? Possible bisect?
Please attach the dmesg booting with drm.debug=0x1e

> 
> -- 
> Jiri Kosina
> SUSE Labs
> 
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