From: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
To: Daniel Vetter <daniel@ffwll.ch>
Cc: Maxime Ripard <maxime.ripard@free-electrons.com>,
Mike Turquette <mturquette@baylibre.com>,
Stephen Boyd <sboyd@codeaurora.org>,
David Airlie <airlied@linux.ie>,
Thierry Reding <thierry.reding@gmail.com>,
Philipp Zabel <p.zabel@pengutronix.de>,
devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, linux-clk@vger.kernel.org,
dri-devel@lists.freedesktop.org, linux-sunxi@googlegroups.com,
Chen-Yu Tsai <wens@csie.org>, Hans de Goede <hdegoede@redhat.com>,
Alexander Kaplan <alex@nextthing.co>,
Boris Brezillon <boris.brezillon@free-electrons.com>,
Wynter Woods <wynter@nextthing.co>,
Thomas Petazzoni <thomas.petazzoni@free-electrons.com>,
Rob Clark <robdclark@gmail.com>
Subject: Re: [PATCH v2 13/26] drm/fb_cma_helper: Remove implicit call to disable_unused_functions
Date: Mon, 25 Jan 2016 00:19:27 +0200 [thread overview]
Message-ID: <1484612.l42nGNbAu5@avalon> (raw)
In-Reply-To: <20160115101730.GH19130@phenom.ffwll.local>
Hi Daniel,
On Friday 15 January 2016 11:17:30 Daniel Vetter wrote:
> On Fri, Jan 15, 2016 at 01:13:05AM +0200, Laurent Pinchart wrote:
> > On Thursday 14 January 2016 16:24:56 Maxime Ripard wrote:
> >> The drm_fbdev_cma_init function always calls the
> >> drm_helper_disable_unused_functions. Since it's part of the usual probe
> >> process, all the drivers using that helper will end up having their
> >> encoder and CRTC disable functions called at probe if their device has
> >> not been reported as enabled.
> >>
> >> This could be fixed by reading out from the registers the current state
> >> of the device if it is enabled, but even that will not handle the case
> >> where the device is actually disabled.
> >>
> >> Moreover, the drivers using the atomic modesetting expect that their
> >> enable and disable callback to be called when the device is already
> >> enabled or disabled (respectively).
> >>
> >> We can however fix this issue by moving the call to
> >> drm_helper_disable_unused_functions out of drm_fbdev_cma_init and make
> >> the drivers needing it (all the drivers calling drm_fbdev_cma_init and
> >> not using the atomic modesetting) explicitly call it.
> >
> > I'd rather add it to all drivers that call drm_fbdev_cma_init(). All the
> > atomic ones must have special code to cope with it that could be rendered
> > useless by the removal of the drm_helper_disable_unused_functions() call.
> > That code should be removed too, and it would be easier to check drivers
> > one by one and fixing them individually (outside of this patch series,
> > unless you insist ;-)) when removing the explicit
> > drm_helper_disable_unused_functions() call.
>
> I had the same thought, but figured there's really no good reason ever to
> do this. I suspect most of that disable_unused_function stuff we have all
> over is supreme cargo-cult anyway ;-)
I'm not sure you got my point. Yes, the drm_helper_disable_unused_functions()
call should be removed from atomic drivers, but that will leave support code
added for the sole reason of avoiding the crash in the drivers. That code will
likely not be noticed and will stay there rotting. If we added
drm_helper_disable_unused_functions() calls to all atomic drivers then driver
authors will hopefully check carefully if there's any support code that can be
removed when removing the function call. It would act as a kind of FIXME
reminder.
> > Other than that the patch looks fine to me.
>
> So went ahead and applied to drm-misc.
--
Regards,
Laurent Pinchart
next prev parent reply other threads:[~2016-01-25 6:22 UTC|newest]
Thread overview: 64+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-01-14 15:24 [PATCH v2 00/26] drm: Add Allwinner A10 display engine support Maxime Ripard
2016-01-14 15:24 ` [PATCH v2 01/26] reset: Move DT cell size check to the core Maxime Ripard
2016-01-15 15:50 ` Philipp Zabel
2016-01-14 15:24 ` [PATCH v2 02/26] reset: Make reset_control_ops const Maxime Ripard
2016-01-15 15:50 ` Philipp Zabel
2016-01-14 15:24 ` [PATCH v2 03/26] clk: Add regmap support Maxime Ripard
2016-01-28 7:56 ` Stephen Boyd
2016-01-14 15:24 ` [PATCH v2 04/26] clk: composite: Add unregister function Maxime Ripard
2016-01-14 15:24 ` [PATCH v2 05/26] clk: sunxi: Add display and TCON0 clocks driver Maxime Ripard
2016-01-15 3:01 ` Rob Herring
2016-01-16 14:08 ` [linux-sunxi] " Priit Laes
2016-01-16 15:29 ` Chen-Yu Tsai
2016-02-03 20:18 ` Maxime Ripard
2016-01-14 15:24 ` [PATCH v2 06/26] clk: sunxi: Add PLL3 clock Maxime Ripard
2016-01-15 3:02 ` Rob Herring
2016-01-16 16:05 ` Chen-Yu Tsai
2016-02-03 20:27 ` Maxime Ripard
2016-01-14 15:24 ` [PATCH v2 07/26] clk: sunxi: Add TCON channel1 clock Maxime Ripard
2016-01-15 3:03 ` Rob Herring
2016-01-16 16:36 ` Chen-Yu Tsai
2016-02-03 20:29 ` Maxime Ripard
2016-01-14 15:24 ` [PATCH v2 08/26] clk: sun5i: add DRAM gates Maxime Ripard
2016-01-15 3:04 ` Rob Herring
2016-01-14 15:24 ` [PATCH v2 09/26] ARM: sun5i: dt: Add pll3 and pll7 clocks Maxime Ripard
2016-01-14 15:24 ` [PATCH v2 10/26] ARM: sun5i: a13: Add display and TCON clocks Maxime Ripard
2016-01-16 17:06 ` Chen-Yu Tsai
2016-02-03 20:31 ` Maxime Ripard
2016-02-05 9:49 ` Chen-Yu Tsai
2016-01-14 15:24 ` [PATCH v2 11/26] ARM: sun5i: Add DRAM gates Maxime Ripard
2016-01-16 17:10 ` Chen-Yu Tsai
2016-02-03 20:36 ` Maxime Ripard
2016-01-14 15:24 ` [PATCH v2 12/26] ARM: sun5i: Add TV encoder gate to the DTSI Maxime Ripard
2016-01-16 17:12 ` Chen-Yu Tsai
2016-01-14 15:24 ` [PATCH v2 13/26] drm/fb_cma_helper: Remove implicit call to disable_unused_functions Maxime Ripard
2016-01-14 23:13 ` Laurent Pinchart
2016-01-15 10:17 ` Daniel Vetter
2016-01-24 22:19 ` Laurent Pinchart [this message]
2016-01-25 7:29 ` Daniel Vetter
2016-01-25 19:02 ` Laurent Pinchart
2016-01-14 15:24 ` [PATCH v2 14/26] drm/modes: Rewrite the command line parser Maxime Ripard
2016-01-14 15:24 ` [PATCH v2 15/26] drm/modes: Support modes names on the command line Maxime Ripard
2016-01-14 15:24 ` [PATCH v2 16/26] drm: Add Allwinner A10 Display Engine support Maxime Ripard
2016-01-16 15:11 ` [linux-sunxi] " Priit Laes
2016-01-17 12:58 ` Priit Laes
2016-01-19 15:38 ` Maxime Ripard
2016-01-14 15:25 ` [PATCH v2 17/26] drm: sun4i: Add DT bindings documentation Maxime Ripard
2016-01-15 3:15 ` Rob Herring
2016-02-03 19:59 ` Maxime Ripard
2016-02-03 20:19 ` Rob Herring
2016-02-03 20:47 ` Maxime Ripard
2016-01-14 15:25 ` [PATCH v2 18/26] drm: sun4i: Add RGB output Maxime Ripard
2016-01-14 15:25 ` [PATCH v2 19/26] drm: sun4i: Add composite output Maxime Ripard
2016-01-14 15:25 ` [PATCH v2 20/26] drm: sun4i: tv: Add PAL output standard Maxime Ripard
2016-01-14 15:25 ` [PATCH v2 21/26] drm: sun4i: tv: Add NTSC " Maxime Ripard
2016-01-14 15:25 ` [PATCH v2 22/26] ARM: sun5i: r8: Add display blocks to the DTSI Maxime Ripard
2016-01-14 15:25 ` [PATCH v2 23/26] ARM: sun5i: chip: Enable the TV Encoder Maxime Ripard
2016-01-14 15:25 ` [PATCH v2 24/26] devicetree: Add olimex vendor prefix Maxime Ripard
2016-01-15 3:15 ` Rob Herring
2016-01-15 6:41 ` Stefan Wahren
2016-01-15 8:05 ` Maxime Ripard
2016-01-14 15:25 ` [PATCH v2 25/26] drm/panel: simple: Add timings for the Olimex LCD-OLinuXino-4.3TS Maxime Ripard
2016-01-15 3:17 ` Rob Herring
2016-01-14 15:25 ` [PATCH v2 26/26] DO NOT MERGE: ARM: sun5i: chip: Enable the LCD panel Maxime Ripard
2016-02-20 13:45 ` [linux-sunxi] [PATCH v2 00/26] drm: Add Allwinner A10 display engine support Priit Laes
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