[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 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.

>
>>
>>
>> > 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?

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
>> >
>> >
>> >
>> > _______________________________________________
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>> > http://lists.freedesktop.org/mailman/listinfo/dri-devel
>> >
>
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