[PATCH RFC 0/2] drm/exynos: refactoring drm device init/deinit

[Inki Dae]

> -----Original Message-----
> From: Andrzej Hajda [mailto:a.hajda at samsung.com]
> Sent: Monday, April 14, 2014 5:55 PM
> To: Inki Dae
> Cc: dri-devel at lists.freedesktop.org; moderated list:ARM/S5P EXYNOS AR...;
> Kyungmin Park; Marek Szyprowski
> Subject: Re: [PATCH RFC 0/2] drm/exynos: refactoring drm device
> init/deinit
> 
> On 04/12/2014 04:18 PM, Inki Dae wrote:
> > Hi Andrzej,
> >
> > Thanks for your contributions.
> >
> > 2014-04-11 23:11 GMT+09:00 Andrzej Hajda <a.hajda at samsung.com>:
> >> Hi Inki,
> >>
> >> This patchset refactors drm device initialization. Details are
> >> described in respective patches. It is an alternative to DT supernode
> concept.
> >>
> >> The first patch uses linker sections to get rid of ifdef macros, it
> >> is not
> > That's a good idea. :) We could avoid ugly #ifdef ~ #endif with this
way.
> >
> >> essential for 2nd patch but it makes code more readable. Similar
> >> approach is used by irqchip, clks and clk_sources.
> > But 2nd patch doesn't seem reasnoable to me. Your approach is same as
> > existing one conceptually. I think we need to handle drm driver in a
> > different way from irqchip, clks and clk_sources.
> >
> > DRM driver means one integrated graphics card but in most embedded
> > systems, graphics and display relevant devices have separated hardware
> > resources. So we would need abstractional integrated hardware,
> > display-subsystem, super device. That is why I are trying to use super
> > device approach, and conceptually it would be right solution. It
> > wouldn't be not good to combine those separated hardware somehow using
> > specific codes.
> 
> Conceptually both approaches are the same: we have number of devices which
> should be ready before we can start super-device and if any device is to
> be removed super-device should be removed before.
> The difference is in 'details':
> - super-node approach have list of components provided explicitly in DT
> special node,
> - in this approach list of components is constructed from devices present
> in the system.
> 
> Creating special DT node with information which is available anyway seems
> to be redundant and against DT rules.
> 

CCing Russell King,

What is the special DT node? You mean device node from ports property?

It is supposed  to use super device and its properties in mainline so I
don't see what it is against DT rules. If they are really against DT rules,
why component framework is in mainline?

As you said above, conceptually both approaches may be the same but your
approach has no any abstract hardware meaning one integrated hardware. And
if conceptually both approaches are the same, it would be good to use
existing infrastructure, component framework so there is no any reason to
add and use specific codes.

And component framework says,
"Subsystems such as ALSA, DRM and others require a single card-level device
structure to represent a subsystem. However, firmware tends to describe the
individual devices and the connections between them. Therefore, we need a
way to gather up the individual component devices together, and indicate
when we have all the component devices."

Thanks,
Inki Dae

> Regarding the old approach, I would not compare it with the current ones
> as it has two main flaws:
> - it is not aware of deferred probing, or more precisely it assumes that
> driver registration instantly triggers device probing (it happens to be
> true) and no probe of drm component will happen later (and this is false
> assumption, eg. deferred probe),
> - it do not remove super-device in case of removal of any of components.
> 
> Regards
> Andrzej
> 
> >
> > I have updated and tested super device approach with existing dt
> > support so there wouldn't be any dt broken issue. I will post next
> > version of this patch series soon, maybe tomorrow or the day after
> > tomorrow.
> >
> > Thanks,
> > Inki Dae
> >
> >> The patchset is based on exynos-drm-next branch.
> >>
> >> Regards
> >> Andrzej
> >>
> >>
> >> Andrzej Hajda (2):
> >>   drm/exynos: refactor drm drivers registration code
> >>   drm/exynos: initialize drm master only when all exynos drm devices
> are
> >>     ready
> >>
> >>  drivers/gpu/drm/exynos/Makefile             |   2 +
> >>  drivers/gpu/drm/exynos/exynos_dp_core.c     |  37 ++--
> >>  drivers/gpu/drm/exynos/exynos_drm.lds.S     |   9 +
> >>  drivers/gpu/drm/exynos/exynos_drm_drv.c     | 279
+++++++++++++--------
> -------
> >>  drivers/gpu/drm/exynos/exynos_drm_drv.h     |  20 +-
> >>  drivers/gpu/drm/exynos/exynos_drm_dsi.c     |  42 +++--
> >>  drivers/gpu/drm/exynos/exynos_drm_fimc.c    |  35 ++--
> >>  drivers/gpu/drm/exynos/exynos_drm_fimd.c    |  38 ++--
> >>  drivers/gpu/drm/exynos/exynos_drm_g2d.c     |  17 +-
> >>  drivers/gpu/drm/exynos/exynos_drm_gsc.c     |  30 +--
> >>  drivers/gpu/drm/exynos/exynos_drm_ipp.c     |  18 +-
> >>  drivers/gpu/drm/exynos/exynos_drm_rotator.c |  27 ++-
> >>  drivers/gpu/drm/exynos/exynos_drm_vidi.c    |  18 +-
> >>  drivers/gpu/drm/exynos/exynos_hdmi.c        |  53 ++++--
> >>  drivers/gpu/drm/exynos/exynos_mixer.c       |  14 +-
> >>  15 files changed, 360 insertions(+), 279 deletions(-)  create mode
> >> 100644 drivers/gpu/drm/exynos/exynos_drm.lds.S
> >>
> >> --
> >> 1.8.3.2
> >>
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