linux-kernel - Re: BUG caused by "Use new drm_fb

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Message-ID: <20160209093240.GF11240@phenom.ffwll.local>
Date:	Tue, 9 Feb 2016 10:32:40 +0100
From:	Daniel Vetter <daniel@...ll.ch>
To:	Michel Dänzer <michel@...nzer.net>
Cc:	Peter Hurley <peter@...leysoftware.com>,
	Archit Taneja <architt@...eaurora.org>,
	Daniel Vetter <daniel.vetter@...ll.ch>,
	Ben Skeggs <bskeggs@...hat.com>,
	Linux kernel <linux-kernel@...r.kernel.org>,
	"dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>
Subject: Re: BUG caused by "Use new drm_fb_helper functions" series

On Wed, Feb 03, 2016 at 06:30:54PM +0900, Michel Dänzer wrote:
> On 03.02.2016 03:38, Peter Hurley wrote:
> > On 02/01/2016 09:20 PM, Archit Taneja wrote:
> >> Hi Peter,
> >>
> >> On 02/02/2016 02:07 AM, Peter Hurley wrote:
> >>> Hi Archit,
> >>>
> >>> Just booting 4.4-rc5+, I got this splat [1]
> >>> At first glance, this appears to be a simple fix.
> >>
> >> Thanks for sharing this.
> >>
> >>>
> >>> However, I'm concerned that fbcon functions, which may be called with
> >>> interrupts disabled, are now hooked up to fbdev functions which may assume
> >>> interrupts are not disabled (as is the case with cfb_imageblit()).
> >>
> >> In the case when CONFIG_FB is enabled, drm_fb_helper_cfb_imageblit
> >> helper simply wraps around cfg_imageblit, so I don't see how we'd have
> >> any difference in behaviour.
> > 
> > 
> > Sorry; terrible attribution on my part.
> > This bug clearly has nothing to do with this series.
> > 
> > But a better look has me wondering how all these gpus are syncing
> > the framebuffer for direct access via cfb_imageblit and friends. I only see
> > nouveau and intel gma even trying.
> 
> Probably no other DRM driver uses hardware acceleration for fbcon.

Yup. We've had patches for i915, resulted in half of mesa+glamour in-kernel, which
is just pointless.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch