linux-kernel - Re: [PATCH 4/8] drm/fb-helper: Add fb_deferred

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Date:	Fri, 22 Apr 2016 19:36:03 +0200
From:	Daniel Vetter <daniel@...ll.ch>
To:	Noralf Trønnes <noralf@...nnes.org>
Cc:	dri-devel <dri-devel@...ts.freedesktop.org>,
	Linux Fbdev development list <linux-fbdev@...r.kernel.org>,
	Laurent Pinchart <laurent.pinchart@...asonboard.com>,
	Tomi Valkeinen <tomi.valkeinen@...com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 4/8] drm/fb-helper: Add fb_deferred_io support

On Fri, Apr 22, 2016 at 7:28 PM, Noralf Trønnes <noralf@...nnes.org> wrote:
> This patch extend the use of the fbdev deferred_io worker to also handle
> the fbdev drawing operations, which can happen in atomic context.
> The qxl driver adds an extra worker (struct qxl_device).fb_work which is
> used to flush the framebuffer. Both the mmap deferred_io (qxl_deferred_io())
> code which is run by the deferred io worker and the fbdev drawing operations
> (qxl_fb_fillrect() etc.) schedule this fb_work worker.
>
> So this patch uses 1 worker, qxl uses 2 workers.

Oh, I didn't realize that you're reusing the same worker for both
things. 2 workers indeed make sense, since the mmap one must have a
built-in delay (to coalesce a bunch of writes), whereas the other one
probably should be run right away, after each op.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch