Re: [PATCH RFC 00/11] drm/tilcdc: Atomic modeset support

From: Tomi Valkeinen <tomi.valkeinen@ti.com>
To: Jyri Sarha <jsarha@ti.com>, dri-devel@lists.freedesktop.org
Cc: laurent.pinchart@ideasonboard.com
Subject: Re: [PATCH RFC 00/11] drm/tilcdc: Atomic modeset support
Date: Mon, 9 May 2016 17:10:00 +0300	[thread overview]
Message-ID: <57309A38.6000702@ti.com> (raw)
In-Reply-To: <cover.1460380199.git.jsarha@ti.com>

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Hi Jyri,

On 11/04/16 19:46, Jyri Sarha wrote:
> The LCDC in its simplicity does not fit too well into DRM atomic
> modeset abstractions. I wonder if I am doing the right thing in
> implementing the dummy primary plane and in implementing
> mode_set_nofb() crtc helper when the crtc actually needs the
> framebuffer to be there when configuring it. See individual patch
> descriptions for details. There is still lot of room for cleaning up
> but I would first like to know if I am moving at all to the right
> direction.

I'm no expert on atomic modesetting, but here are my comments/questions:

You add drm_crtc_vblank_off() to crtc_destroy() callback. Why is that? I
think you should call drm_crtc_vblank_on() in crtc_enable(), and
vblank_off in disable.

You remove the setting of tilcdc_crtc_helper_funcs.dpms, but leave the
tilcdc_crtc_dpms, which you use elsewhere. I think all dpms stuff should
be removed from crtc, as it's all either "enable" or "disable". Git grep
shows that in omapdrm, there's just one reference to dpms, in
omap_connector.c: .dpms = drm_atomic_helper_connector_dpms

It's not clear to me if a (primary) plane is required with atomic
universal planes and modesetting or not... I guess it is, when thinking
of how e.g. a framebuffer is configured to be shown on a screen when
using the atomic modesetting uapi.

But if it is required, it makes me wonder, are there other HWs out there
without any planes? The dummy plane implementation you added is not
complex, but is it something that should be implemented with DRM helper
funcs?

 Tomi

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