[PATCH v2 12/26] drm/exynos: Split manager/display/subdrv

[Inki Dae]

2013/10/23 Stéphane Marchesin <stephane.marchesin at gmail.com>:
>
>
>
> On Tue, Oct 22, 2013 at 9:15 PM, Inki Dae <inki.dae at samsung.com> wrote:
>>
>> 2013/10/23 Stéphane Marchesin <stephane.marchesin at gmail.com>:
>> >
>> >
>> >
>> > On Tue, Oct 22, 2013 at 8:38 PM, Inki Dae <inki.dae at samsung.com> wrote:
>> >>
>> >> 2013/10/23 Stéphane Marchesin <stephane.marchesin at gmail.com>:
>> >> >
>> >> >
>> >> >
>> >> > On Tue, Oct 22, 2013 at 7:28 PM, Inki Dae <inki.dae at samsung.com>
>> >> > wrote:
>> >> >>
>> >> >> 2013/10/22 Sean Paul <seanpaul at chromium.org>:
>> >> >> > On Tue, Oct 22, 2013 at 1:30 AM, Inki Dae <inki.dae at samsung.com>
>> >> >> > wrote:
>> >> >> >>
>> >> >> >>
>> >> >> >>> -----Original Message-----
>> >> >> >>> From: Sean Paul [mailto:seanpaul at chromium.org]
>> >> >> >>> Sent: Tuesday, October 22, 2013 6:18 AM
>> >> >> >>> To: Inki Dae
>> >> >> >>> Cc: dri-devel; Dave Airlie; Tomasz Figa; Stéphane Marchesin
>> >> >> >>> Subject: Re: [PATCH v2 12/26] drm/exynos: Split
>> >> >> >>> manager/display/subdrv
>> >> >> >>>
>> >> >> >>> On Mon, Oct 21, 2013 at 10:46 AM, Sean Paul
>> >> >> >>> <seanpaul at chromium.org>
>> >> >> >>> wrote:
>> >> >> >>> > On Thu, Oct 17, 2013 at 10:31 PM, Inki Dae
>> >> >> >>> > <inki.dae at samsung.com>
>> >> >> >>> > wrote:
>> >> >> >>> >>
>> >> >> >>> >>
>> >> >> >>> >>> -----Original Message-----
>> >> >> >>> >>> From: Sean Paul [mailto:seanpaul at chromium.org]
>> >> >> >>> >>> Sent: Thursday, October 17, 2013 11:37 PM
>> >> >> >>> >>> To: Inki Dae
>> >> >> >>> >>> Cc: dri-devel; Dave Airlie; Tomasz Figa; Stéphane Marchesin
>> >> >> >>> >>> Subject: Re: [PATCH v2 12/26] drm/exynos: Split
>> >> >> >>> >>> manager/display/subdrv
>> >> >> >>> >>>
>> >> >> >>> >>> On Thu, Oct 17, 2013 at 4:21 AM, Inki Dae
>> >> >> >>> >>> <inki.dae at samsung.com>
>> >> >> >> wrote:
>> >> >> >>> >>> >
>> >> >> >>> >>> >
>> >> >> >>> >>> >> -----Original Message-----
>> >> >> >>> >>> >> From: Sean Paul [mailto:seanpaul at chromium.org]
>> >> >> >>> >>> >> Sent: Thursday, October 17, 2013 4:27 AM
>> >> >> >>> >>> >> To: dri-devel at lists.freedesktop.org; inki.dae at samsung.com
>> >> >> >>> >>> >> Cc: airlied at linux.ie; tomasz.figa at gmail.com;
>> >> >> >>> >>> >> marcheu at chromium.org;
>> >> >> >>> Sean
>> >> >> >>> >>> >> Paul
>> >> >> >>> >>> >> Subject: [PATCH v2 12/26] drm/exynos: Split
>> >> >> >>> >>> >> manager/display/subdrv
>> >> >> >>> >>> >>
>> >> >> >>> >>> >> This patch splits display and manager from subdrv. The
>> >> >> >>> >>> >> result
>> >> >> >>> >>> >> is
>> >> >> >>> that
>> >> >> >>> >>> >> crtc functions can directly call into manager callbacks
>> >> >> >>> >>> >> and
>> >> >> >>> >>> >> encoder
>> >> >> >>> >>> >> functions can directly call into display callbacks. This
>> >> >> >>> >>> >> will
>> >> >> >>> >>> >> allow
>> >> >> >>> >>> >> us to remove the exynos_drm_hdmi shim and support
>> >> >> >>> >>> >> mixer/hdmi
>> >> >> >>> >>> >> &
>> >> >> >>> fimd/dp
>> >> >> >>> >>> >> with common code.
>> >> >> >>> >>> >>
>> >> >> >>> >>> >> Signed-off-by: Sean Paul <seanpaul at chromium.org>
>> >> >> >>> >>> >> ---
>> >> >> >>> >>> >>
>> >> >> >>> >>> >> Changes in v2:
>> >> >> >>> >>> >>       - Pass display into display_ops instead of context
>> >> >> >>> >>> >
>> >> >> >>> >>> > Sorry but it seems like more reasonable to pass device
>> >> >> >>> >>> > object
>> >> >> >>> >>> > into
>> >> >> >>> >>> > display_ops and manager_ops.
>> >> >> >>> >>> >
>> >> >> >>> >>>
>> >> >> >>> >>>
>> >> >> >>> >>> So you've changed your mind from when you said the
>> >> >> >>> >>> following?
>> >> >> >>> >>>
>> >> >> >>> >>> >>> manager->ops->xxx(manager, ...);
>> >> >> >>> >>> >>> display->ops->xxx(display, ...);
>> >> >> >>> >>> >>>
>> >> >> >>> >>> >>> Agree.
>> >> >> >>> >>>
>> >> >> >>> >>
>> >> >> >>> >>
>> >> >> >>> >> True. Before that, My comment was to pass device object into
>> >> >> >>> display_ops and
>> >> >> >>> >> manager_ops, and then you said the good solution is to pass
>> >> >> >>> >> manager
>> >> >> >>> >> and
>> >> >> >>> >> display to each driver. At that time, I thought no matter how
>> >> >> >>> >> the
>> >> >> >>> callback
>> >> >> >>> >> is called if the framework doesn't call callbacks of each
>> >> >> >>> >> driver
>> >> >> >>> >> with
>> >> >> >>> ctx.
>> >> >> >>> >> So I agreed.
>> >> >> >>> >>
>> >> >> >>> >>
>> >> >> >>> >>> It would have been nice if you had changed your mind
>> >> >> >>> >>> *before* I
>> >> >> >>> >>> reworked everything. At any rate, I think it's still the
>> >> >> >>> >>> right
>> >> >> >>> >>> thing
>> >> >> >>> >>> to do.
>> >> >> >>> >>
>> >> >> >>> >> Really sorry about that. And I will add new patch for it so
>> >> >> >>> >> you
>> >> >> >>> >> don't
>> >> >> >>> need
>> >> >> >>> >> to concern about that.
>> >> >> >>> >>
>> >> >> >>> >>>
>> >> >> >>> >>>
>> >> >> >>> >>> > I'm not sure but display_ops could be implemented in other
>> >> >> >>> >>> > framework
>> >> >> >>> >>> based
>> >> >> >>> >>> > driver such as CDF based lcd panel driver. So if you pass
>> >> >> >>> >>> > display -
>> >> >> >>> it's
>> >> >> >>> >>> > specific to exynos drm framework - into display_ops, the
>> >> >> >>> >>> > other
>> >> >> >>> framework
>> >> >> >>> >>> > based driver should include specific exynos drm header.
>> >> >> >>> >>> >
>> >> >> >>> >>>
>> >> >> >>> >>> AFAIK, CDF will not land in its current separate-from-drm
>> >> >> >>> >>> form,
>> >> >> >>> >>> we
>> >> >> >>> >>> don't need to worry about this. Furthermore, these ops
>> >> >> >>> >>> should
>> >> >> >>> >>> just
>> >> >> >>> >>> go
>> >> >> >>> >>> away and become drm_crtc/drm_encoder/drm_connector funcs
>> >> >> >>> >>> anyways.
>> >> >> >>> >>>
>> >> >> >>> >>
>> >> >> >>> >> Can you assure the display_ops never implemented in other
>> >> >> >>> >> framework
>> >> >> >>> based
>> >> >> >>> >> driver, not CDF? At any rate, I think all possibilities
>> >> >> >>> >> should
>> >> >> >>> >> be
>> >> >> >>> opened.
>> >> >> >>> >>
>> >> >> >>> >
>> >> >> >>> > I don't think we should let an RFC framework make the code
>> >> >> >>> > more
>> >> >> >>> > complicated for unclear benefit. By removing manager/display
>> >> >> >>> > entirely,
>> >> >> >>> > we can get rid of a *lot* of other code that is basically just
>> >> >> >>> > plumbing drm hooks (exynos_drm_connector is a good example).
>> >> >> >>> >
>> >> >> >>>
>> >> >> >>> I hacked this up today to prove it out. Check out the top 5
>> >> >> >>> commits
>> >> >> >>> in
>> >> >> >>>
>> >> >> >>>
>> >> >> >>>
>> >> >> >>> https://github.com/crseanpaul/exynos-drm-next/commits/linux-next-exynos-
>> >> >> >>> staging.
>> >> >> >>> It removes exynos_drm_connector in favor of just implementing
>> >> >> >>> drm_connector directly. This same treatment should be done for
>> >> >> >>> exynos_drm_encoder and exynos_drm_crtc, but I didn't get around
>> >> >> >>> to
>> >> >> >>> doing this.
>> >> >> >>>
>> >> >> >>> As you can see, it cuts out a lot of code and removes an entire
>> >> >> >>> abstraction layer. Much nicer :)
>> >> >> >>>
>> >> >> >>
>> >> >> >> It seems that you implements connector in each device driver.
>> >> >> >> Can't
>> >> >> >> they be
>> >> >> >> combined as common spot, exynos_connector, again to avoid codes
>> >> >> >> from
>> >> >> >> duplicated? :)
>> >> >> >
>> >> >> > There's nothing of substance being duplicated.
>> >> >>
>> >> >> Not true. xxx_create_connector is duplicated.
>> >> >>
>> >> >> > In fact, by getting rid
>> >> >> > of the exynos_drm_connector layer, we deleted 150 lines. If you
>> >> >> > really
>> >> >> > take a look at exynos_drm_connector, it's not doing anything
>> >> >> > useful.
>> >> >>
>> >> >> No, That is for each driver has no any dependency of drm framework.
>> >> >>
>> >> >> > All it does is translate the drm callbacks into display callbacks,
>> >> >> > so
>> >> >> > I think it's much better to just implement the drm callbacks
>> >> >> > directly.
>> >> >> >
>> >> >>
>> >> >> No, It has strongly dependency of drm framework. Assume that we
>> >> >> implemented the drm callbacks directly, and then some features are
>> >> >> added to drm framework, drm_connector side. At this time, we will
>> >> >> have
>> >> >> to take care of each device driver according to the change. That is
>> >> >> really not good. Why device drivers should have dependency of drm
>> >> >> framework? Just to reduce line counts?
>> >> >
>> >> >
>> >> >
>> >> > You seem to miss the point here and elsewhere in the discussion.
>> >> > drm/exynos is a drm driver, and as such it should use the drm
>> >> > framework,
>> >>
>> >> Hm.. you seem to miss something. Exynos drm based drivers are based on
>> >> exynos drm framework, not drm framework directly. So I mean that
>> >> Exynos drm framework based drivers should include only Exynos drm
>> >> headers, _not drm header_ directly.
>> >
>> >
>> > Well, I think everyone sees that exynos is different. But my point still
>> > remains: why is the exynos driver in drm/ if it wants to use a different
>> > framework? Right now it is blocking work on a proper drm driver...
>> >
>>
>> Noooooo. It's not to use a different framework. It's to use a wrapper
>> instead.
>
>
> Ok, if you want to call it a wrapper, then what is the point of doing this
> wrapping given that it prevents a proper drm-style implementation?
>

I already commented. That is for only Exynos drm framework has
dependency of drm framework directly, and Exynos drm based drivers
include only Exynos drm headers.

>
>>
>> >
>> >>
>> >>
>> >> > especially if this reduces the line count and the code
>> >> > complexity (as is the case for this patch series). If you don't want
>> >> > to maintain a drm driver, it simply should be moved away from drm/,
>> >> > and it should be replaced by a real drm driver in my opinion.
>> >>
>> >> So those drivers should be in drm/exynos. Isn't that you really mean
>> >> those drivers should be driver/gpu/drm?
>> >
>> >
>> > I don't understand this sentence, sorry.
>>
>> Sorry, again, you mean Exynos drm based drivers should be in
>> drivers/gpu/drm, not drivers/gpu/drm/exynos?
>>
> Is the exynos drm useful in its current shape at all? My recommendation
> would be to fork off a real drm driver in gpu/drm/exynos with the current
> code as a base.
>

Yes as of now. of course, There could be a better way. However, I
don't want for Exynos drm based drivers have dependency of drm
framework directly.

Thanks for your opinions.
Inki Dae

> Stéphane
>
>
>>
>> Thanks,
>> Inki Dae
>>
>> >
>> > Stéphane
>> >
>> >
>> >>
>> >> If so, That would really be
>> >> horrible. :(
>> >>
>> >
>> >
>> >>
>> >> Please, know that only Exynos drm framework, _not device drivers_, has
>> >> all dependencies of drm framework, and also I know that other ARM
>> >> based drm drivers are using same way.
>> >>
>> >> Thanks,
>> >> Inki Dae
>> >>
>> >> >
>> >> > Stéphane
>> >> >
>> >> >>
>> >> >>
>> >> >> > There are a bunch of real bugs that we've found as a result of
>> >> >> > having
>> >> >> > these abstraction layers. Take, for example, dpms. Before this
>> >> >> > patchset, dpms for fimd was being tracked separately in fimd
>> >> >> > driver,
>> >> >> > exynos_drm_encoder, exynos_drm_crtc, and exynos_drm_connector.
>> >> >> > Furthermore, during suspend, only fimd driver's dpms state was
>> >> >> > updated, so the others were incorrect. There was also this weird
>> >> >> > gymnastics that had to happen when dpms was changed in the encoder
>> >> >> > since it had to walk up to the connector level to change its dpms
>> >> >> > state. If fimd just directly implemented
>> >> >> > drm_crtc/drm_encoder/drm_connector (before dp was moved in), this
>> >> >> > problem wouldn't exist. The same goes for HDMI/mixer.
>> >> >> >
>> >> >>
>> >> >> That is a issue we should take care of by using the independent
>> >> >> layer.
>> >> >> Then, aren't you take care of that well with the re-factoring patch
>> >> >> set? :)  It seems that you are outside real point.
>> >> >>
>> >> >> > Take a look at exynos_drm_encoder.c  in my tree
>> >> >> >
>> >> >> >
>> >> >> >
>> >> >> > (https://github.com/crseanpaul/exynos-drm-next/blob/linux-next-exynos-staging/drivers/gpu/drm/exynos/exynos_drm_encoder.c),
>> >> >> > what does it do that's useful to abstract? All that it does is
>> >> >> > just
>> >> >> > call display ops, it's completely useless. The same is true for
>> >> >> > exynos_drm_connector, it's just dead weight. There is some useful
>> >> >> > stuff in exynos_drm_crtc for page flipping, that would be better
>> >> >> > served as a helper library, though.
>> >> >> >
>> >> >> >> The abstraction layer you mentioned also means a common spot.
>> >> >> >> Another one, you patch also makes each sub driver have strongly
>> >> >> >> dependency
>> >> >> >> of drm framework. So how we can support existing backlight and
>> >> >> >> lcd
>> >> >> >> class
>> >> >> >> based lcd panel drivers if the connector is implemented in each
>> >> >> >> device
>> >> >> >> driver later?  the drm header files should be included in
>> >> >> >> drivers/video/backlight/xxx_lcd.c?
>> >> >> >>
>> >> >> >
>> >> >> > drm_bridge or drm_panel seem like good candidates for this.
>> >> >> >
>> >> >>
>> >> >> Yes, exynos_drm_display could be replaced with drm_panel later if
>> >> >> the
>> >> >> drm_panel can be merged to mainline.
>> >> >>
>> >> >> >
>> >> >> >> And, I will introduce a new framework to support existing lcd
>> >> >> >> panel
>> >> >> >> drivers
>> >> >> >> and display bus drivers soon; as of now for Exynos drm, and the
>> >> >> >> framework is
>> >> >> >> being tested internally. With this framework, encoder and
>> >> >> >> connector
>> >> >> >> will be
>> >> >> >> created when lcd panel or display bus driver such as eDP is
>> >> >> >> probed:
>> >> >> >> it
>> >> >> >> doesn’t really need to create encoder and connector in advance if
>> >> >> >> lcd
>> >> >> >> panel
>> >> >> >> or display bus driver isn't probed yet. Regardless of crtc, and
>> >> >> >> encoder
>> >> >> >> and
>> >> >> >> connector creation order, when last one is created, crtc and
>> >> >> >> connector
>> >> >> >> will
>> >> >> >> be connected each other. And exynos_drm_display could be
>> >> >> >> implemented
>> >> >> >> in
>> >> >> >> other frameworks if we have common structure for display device
>> >> >> >> driver.
>> >> >> >> And
>> >> >> >> also the framework will support lvds driver according to Linux
>> >> >> >> device
>> >> >> >> driver
>> >> >> >> model.
>> >> >> >>
>> >> >> >
>> >> >> > I don't really follow what you're trying to do here, but I think
>> >> >> > we
>> >> >> > should be moving in the direction of fewer abstractions in the
>> >> >> > exynos
>> >> >> > driver, not more :)
>> >> >> >
>> >> >>
>> >> >> Not abstraction layer, just a bridge for connecting crtc and its
>> >> >> corresponding encoder/connector, and lvds regardless of creation
>> >> >> order, and for connecting drm connector and other framework based
>> >> >> display ops such as drm_panel later.
>> >> >>
>> >> >> > Sean
>> >> >> >
>> >> >> >
>> >> >> >
>> >> >> >> Thanks,
>> >> >> >> Inki Dae
>> >> >> >>
>> >> >> >>> Sean
>> >> >> >>>
>> >> >> >>> >>>
>> >> >> >>> >>> > And another one, the patch 6 passes manager object to
>> >> >> >>> >>> > manager_ops,
>> >> >> >>> and
>> >> >> >>> >>> for
>> >> >> >>> >>> > this, you made the manager object to be set to driver
>> >> >> >>> >>> > data;
>> >> >> >>> >>> > platform_set_drvdata(pdev, &manager). That isn't
>> >> >> >>> >>> > reasonable.
>> >> >> >>> Generally,
>> >> >> >>> >>> > driver_data would point to device driver's context object.
>> >> >> >>> >>> >
>> >> >> >>> >>>
>> >> >> >>> >>> I'm not sure why this isn't reasonable, but it's a moot
>> >> >> >>> >>> point.
>> >> >> >>> >>> The
>> >> >> >>> >>> driver data is only used up until we get rid of the pm ops,
>> >> >> >>> >>> it
>> >> >> >>> >>> needn't
>> >> >> >>> >>> be set at all once things go through dpms.
>> >> >> >>> >>>
>> >> >> >>> >>
>> >> >> >>> >> Generally, device drivers can call its own internal
>> >> >> >>> >> functions,
>> >> >> >>> >> and
>> >> >> >>> >> they
>> >> >> >>> will
>> >> >> >>> >> call that functions with ctx. However, if you set manager to
>> >> >> >>> driver_data
>> >> >> >>> >> then that functions should be called with manager object and
>> >> >> >>> >> also
>> >> >> >>> internally
>> >> >> >>> >> that functions should get ctx from the manager object. What
>> >> >> >>> >> is
>> >> >> >>> >> the
>> >> >> >>> purpose
>> >> >> >>> >> of manager? Do you think it's reasonable?
>> >> >> >>> >>
>> >> >> >>> >
>> >> >> >>> > So, to avoid setting the manager as the drvdata, we could
>> >> >> >>> > implement
>> >> >> >>> > something like fimd_dpms_ctx(ctx, mode) that takes ctx and the
>> >> >> >>> > manager
>> >> >> >>> > callback calls it fimd_dpms(mgr, mode) { ctx = mgr->ctx;
>> >> >> >>> > fimd_dpms_ctx(ctx, mode); }. Alternatively, you can save a
>> >> >> >>> > pointer
>> >> >> >>> > to
>> >> >> >>> > mgr in ctx, but that creates a circular link between the two.
>> >> >> >>> > IMO,
>> >> >> >>> > both of those solutions suck :)
>> >> >> >>> >
>> >> >> >>> > I'd much rather just set drvdata to the manager and call the
>> >> >> >>> > hook
>> >> >> >>> > directly. Like I said earlier, this is just a temporary step
>> >> >> >>> > since
>> >> >> >>> > we
>> >> >> >>> > remove these pm ops later in the patch series.
>> >> >> >>> >
>> >> >> >>> > Sean
>> >> >> >>> >
>> >> >> >>> >
>> >> >> >>> >> Anyway, I'd like to say really sorry about inconvenient
>> >> >> >>> >> again.
>> >> >> >>> >> So I
>> >> >> >>> will fix
>> >> >> >>> >> it.
>> >> >> >>> >>
>> >> >> >>> >> Thanks,
>> >> >> >>> >> Inki Dae
>> >> >> >>> >>
>> >> >> >>> >>> Sean
>> >> >> >>> >>>
>> >> >> >>> >>>
>> >> >> >>> >>> > Thanks,
>> >> >> >>> >>> > Inki Dae
>> >> >> >>> >>> >
>> >> >> >>> >>
>> >> >> >>
>> >> >> > _______________________________________________
>> >> >> > dri-devel mailing list
>> >> >> > dri-devel at lists.freedesktop.org
>> >> >> > http://lists.freedesktop.org/mailman/listinfo/dri-devel
>> >> >> _______________________________________________
>> >> >> dri-devel mailing list
>> >> >> dri-devel at lists.freedesktop.org
>> >> >> http://lists.freedesktop.org/mailman/listinfo/dri-devel
>> >> >
>> >> >
>> >> >
>> >> > _______________________________________________
>> >> > dri-devel mailing list
>> >> > dri-devel at lists.freedesktop.org
>> >> > http://lists.freedesktop.org/mailman/listinfo/dri-devel
>> >> >
>> >
>> >
>> >
>> > _______________________________________________
>> > dri-devel mailing list
>> > dri-devel at lists.freedesktop.org
>> > http://lists.freedesktop.org/mailman/listinfo/dri-devel
>> >
>
>
>
> _______________________________________________
> dri-devel mailing list
> dri-devel at lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/dri-devel
>