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

[Sean Paul]

On Wed, Oct 23, 2013 at 12:48 AM, Inki Dae <inki.dae at samsung.com> wrote:
> 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.
>

Just to satisfy my curiosity, do you actually have something that uses
these drivers outside of drm?

So I think we've reached somewhat of an impasse. I'd like to move the
driver towards a proper drm driver (ie: no exynos
framework/wrapper/whatever), you'd like to keep things separate. So
should we create a new exynos driver drivers/drm/gpu/exynos5 to house
the drm driver?

Sean


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