Re: [PATCH 1/2] drm/mxsfb: Call drm_crtc_vblank_on/off

[Stefan Agner <stefan@agner.ch>]

On 2020-05-28 10:06, Daniel Vetter wrote:
> On Thu, May 28, 2020 at 9:56 AM Stefan Agner <stefan@agner.ch> wrote:
>>
>> Hi Daniel,
>>
>> On 2020-05-28 07:46, Daniel Vetter wrote:
>> > On Wed, May 27, 2020 at 11:47:56AM +0200, Daniel Vetter wrote:
>> >> mxsfb has vblank support, is atomic, but doesn't call
>> >> drm_crtc_vblank_on/off as it should. Not good.
>> >>
>> >> With my next patch to add the drm_crtc_vblank_reset to helpers this
>> >> means not even the very first crtc enabling will vblanks work anymore,
>> >> since they'll just stay off forever.
>> >>
>> >> Since mxsfb doesn't have any vblank waits of its own in the
>> >> enable/disable flow, nor an enable/disable_vblank callback we can do
>> >> the on/off as the first respectively last operation, and it should all
>> >> work.
>> >>
>> >> Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
>> >> Cc: Marek Vasut <marex@denx.de>
>> >> Cc: Stefan Agner <stefan@agner.ch>
>> >> Cc: Shawn Guo <shawnguo@kernel.org>
>> >> Cc: Sascha Hauer <s.hauer@pengutronix.de>
>> >> Cc: Pengutronix Kernel Team <kernel@pengutronix.de>
>> >> Cc: Fabio Estevam <festevam@gmail.com>
>> >> Cc: NXP Linux Team <linux-imx@nxp.com>
>> >> Cc: linux-arm-kernel@lists.infradead.org
>> >
>> > Ping for some ack/review on this one here, it's holding up the subsystem
>> > wide fix in patch 2.
>>
>> Sorry for the delay.
>>
>> I guess that has the same effect as patch 14 in Laurent's patchset would
>> have:
>> https://lore.kernel.org/dri-devel/20200309195216.31042-15-laurent.pinchart@ideasonboard.com/
> 
> Uh, looking at that patch I realized that mxsfb indeed calls
> drm_vblank_init before mode_config.num_crtc is set. Which means it
> never had working vblank support in upstream. That also explains the
> lack of fireworks, since all other drivers that actually do initialize
> vblank support have the drm_crtc_vblank_on/off calls - without them
> the driver doesn't survive for very long.
> 
> tldr; I don't need this patch here to apply the 2nd one, so no
> conflict potential at all. And the patch from Laurent does fix up
> everything correctly, so we should be good.

Uh I see, that is somehow unfortunate and fortunate at the same time!

Ok, I hope we get this cleaned up soon.

--
Stefan

> -Daniel
> 
>> But should be rather trivial to rebase. So until Laurent's patchset is
>> ready, we can go with this fix.
>>
>> Acked-by: Stefan Agner <stefan@agner.ch>
>>
>> --
>> Stefan
>>
>> >
>> > Thanks, Daniel
>> >
>> >> ---
>> >>  drivers/gpu/drm/mxsfb/mxsfb_drv.c | 2 ++
>> >>  1 file changed, 2 insertions(+)
>> >>
>> >> diff --git a/drivers/gpu/drm/mxsfb/mxsfb_drv.c b/drivers/gpu/drm/mxsfb/mxsfb_drv.c
>> >> index 497cf443a9af..1891cd6deb2f 100644
>> >> --- a/drivers/gpu/drm/mxsfb/mxsfb_drv.c
>> >> +++ b/drivers/gpu/drm/mxsfb/mxsfb_drv.c
>> >> @@ -124,6 +124,7 @@ static void mxsfb_pipe_enable(struct drm_simple_display_pipe *pipe,
>> >>      drm_panel_prepare(mxsfb->panel);
>> >>      mxsfb_crtc_enable(mxsfb);
>> >>      drm_panel_enable(mxsfb->panel);
>> >> +    drm_crtc_vblank_on(&pipe->crtc);
>> >>  }
>> >>
>> >>  static void mxsfb_pipe_disable(struct drm_simple_display_pipe *pipe)
>> >> @@ -133,6 +134,7 @@ static void mxsfb_pipe_disable(struct drm_simple_display_pipe *pipe)
>> >>      struct drm_crtc *crtc = &pipe->crtc;
>> >>      struct drm_pending_vblank_event *event;
>> >>
>> >> +    drm_crtc_vblank_off(&pipe->crtc);
>> >>      drm_panel_disable(mxsfb->panel);
>> >>      mxsfb_crtc_disable(mxsfb);
>> >>      drm_panel_unprepare(mxsfb->panel);
>> >> --
>> >> 2.26.2
>> >>
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