[PATCH RFC] drm/atomic: Fall back to legacy call back in *_connector_dpms()

[PATCH RFC] drm/atomic: Fall back to legacy call back in *_connector_dpms()

[Jyri Sarha]

Fall back to legacy drm_helper_connector_dpms() call back in
drm_atomic_helper_connector_dpms() if DRIVER_ATOMIC feature is not
present.

Calling drm_atomic_helper_connector_dpms() from non atomic driver
causes undefined behavior. This is a problem with componentized
encoder/connector drivers that may be bound to both atomic and
non atomic drivers.

Signed-off-by: Jyri Sarha <jsarha@ti.com>
---
This is just an alternative to this:
https://lists.freedesktop.org/archives/dri-devel/2016-January/098867.html

Either one of the patches should be taken for Beaglebone-black, or any
other non atomic driver using tda998x, to work.

 drivers/gpu/drm/drm_atomic_helper.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
index 57cccd6..6ad0303 100644
--- a/drivers/gpu/drm/drm_atomic_helper.c
+++ b/drivers/gpu/drm/drm_atomic_helper.c
@@ -2344,6 +2344,9 @@ int drm_atomic_helper_connector_dpms(struct drm_connector *connector,
 	bool active = false;
 	int old_mode = connector->dpms;
 
+	if (!drm_core_check_feature(connector->dev, DRIVER_ATOMIC))
+		return drm_helper_connector_dpms(connector, mode);
+
 	if (mode != DRM_MODE_DPMS_ON)
 		mode = DRM_MODE_DPMS_OFF;
 
-- 
1.9.1

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Re: [PATCH RFC] drm/atomic: Fall back to legacy call back in *_connector_dpms()

[Daniel Vetter]

On Fri, Feb 12, 2016 at 05:17:19PM +0200, Jyri Sarha wrote:
> Fall back to legacy drm_helper_connector_dpms() call back in
> drm_atomic_helper_connector_dpms() if DRIVER_ATOMIC feature is not
> present.
> 
> Calling drm_atomic_helper_connector_dpms() from non atomic driver
> causes undefined behavior. This is a problem with componentized
> encoder/connector drivers that may be bound to both atomic and
> non atomic drivers.
> 
> Signed-off-by: Jyri Sarha <jsarha@ti.com>
> ---
> This is just an alternative to this:
> https://lists.freedesktop.org/archives/dri-devel/2016-January/098867.html

I like the linked patch much better, since non-atomic really should die.
Inflicting non-atomic on atomic helpers is bad imo, so nack from me on
this patch here.
-Daniel
> 
> Either one of the patches should be taken for Beaglebone-black, or any
> other non atomic driver using tda998x, to work.
> 
>  drivers/gpu/drm/drm_atomic_helper.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
> index 57cccd6..6ad0303 100644
> --- a/drivers/gpu/drm/drm_atomic_helper.c
> +++ b/drivers/gpu/drm/drm_atomic_helper.c
> @@ -2344,6 +2344,9 @@ int drm_atomic_helper_connector_dpms(struct drm_connector *connector,
>  	bool active = false;
>  	int old_mode = connector->dpms;
>  
> +	if (!drm_core_check_feature(connector->dev, DRIVER_ATOMIC))
> +		return drm_helper_connector_dpms(connector, mode);
> +
>  	if (mode != DRM_MODE_DPMS_ON)
>  		mode = DRM_MODE_DPMS_OFF;
>  
> -- 
> 1.9.1
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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Re: [PATCH RFC] drm/atomic: Fall back to legacy call back in *_connector_dpms()

[Tomi Valkeinen]

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On 12/02/16 17:34, Daniel Vetter wrote:
> On Fri, Feb 12, 2016 at 05:17:19PM +0200, Jyri Sarha wrote:
>> Fall back to legacy drm_helper_connector_dpms() call back in
>> drm_atomic_helper_connector_dpms() if DRIVER_ATOMIC feature is not
>> present.
>>
>> Calling drm_atomic_helper_connector_dpms() from non atomic driver
>> causes undefined behavior. This is a problem with componentized
>> encoder/connector drivers that may be bound to both atomic and
>> non atomic drivers.
>>
>> Signed-off-by: Jyri Sarha <jsarha@ti.com>
>> ---
>> This is just an alternative to this:
>> https://lists.freedesktop.org/archives/dri-devel/2016-January/098867.html
> 
> I like the linked patch much better, since non-atomic really should die.
> Inflicting non-atomic on atomic helpers is bad imo, so nack from me on
> this patch here.

I mostly agree, but we are in a transition period from non-atomic to
atomic. When all drivers have been converted to atomic, it should be
easy to grep for code using DRIVER_ATOMIC (or similar), and remove all
the non-atomic support code.

In my opinion it should be considered case by case if the
non-atomic/atomic compat code should be added to the generic functions
or to all the drivers using that functionality.

In this case, if it only affects tda998x (but does it?), perhaps the
patch in the link is better.

 Tomi


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Re: [PATCH RFC] drm/atomic: Fall back to legacy call back in *_connector_dpms()

[Ville Syrjälä]

On Fri, Feb 12, 2016 at 07:08:46PM +0200, Tomi Valkeinen wrote:
> On 12/02/16 17:34, Daniel Vetter wrote:
> > On Fri, Feb 12, 2016 at 05:17:19PM +0200, Jyri Sarha wrote:
> >> Fall back to legacy drm_helper_connector_dpms() call back in
> >> drm_atomic_helper_connector_dpms() if DRIVER_ATOMIC feature is not
> >> present.
> >>
> >> Calling drm_atomic_helper_connector_dpms() from non atomic driver
> >> causes undefined behavior. This is a problem with componentized
> >> encoder/connector drivers that may be bound to both atomic and
> >> non atomic drivers.
> >>
> >> Signed-off-by: Jyri Sarha <jsarha@ti.com>
> >> ---
> >> This is just an alternative to this:
> >> https://lists.freedesktop.org/archives/dri-devel/2016-January/098867.html
> > 
> > I like the linked patch much better, since non-atomic really should die.
> > Inflicting non-atomic on atomic helpers is bad imo, so nack from me on
> > this patch here.
> 
> I mostly agree, but we are in a transition period from non-atomic to
> atomic. When all drivers have been converted to atomic, it should be
> easy to grep for code using DRIVER_ATOMIC (or similar), and remove all
> the non-atomic support code.
> 
> In my opinion it should be considered case by case if the
> non-atomic/atomic compat code should be added to the generic functions
> or to all the drivers using that functionality.
> 
> In this case, if it only affects tda998x (but does it?), perhaps the
> patch in the link is better.

Maybe we need a hybrid helper that just calls the atomic
or non-atomic helper approppriately.

-- 
Ville Syrjälä
Intel OTC
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Re: [PATCH RFC] drm/atomic: Fall back to legacy call back in *_connector_dpms()

[Jyri Sarha]

On 02/12/16 19:15, Ville Syrjälä wrote:
> On Fri, Feb 12, 2016 at 07:08:46PM +0200, Tomi Valkeinen wrote:
>> On 12/02/16 17:34, Daniel Vetter wrote:
>>> On Fri, Feb 12, 2016 at 05:17:19PM +0200, Jyri Sarha wrote:
>>>> Fall back to legacy drm_helper_connector_dpms() call back in
>>>> drm_atomic_helper_connector_dpms() if DRIVER_ATOMIC feature is not
>>>> present.
>>>>
>>>> Calling drm_atomic_helper_connector_dpms() from non atomic driver
>>>> causes undefined behavior. This is a problem with componentized
>>>> encoder/connector drivers that may be bound to both atomic and
>>>> non atomic drivers.drm-next-tilcdc-fixes
>>>>
>>>> Signed-off-by: Jyri Sarha <jsarha@ti.com>
>>>> ---
>>>> This is just an alternative to this:
>>>> https://lists.freedesktop.org/archives/dri-devel/2016-January/098867.html
>>>
>>> I like the linked patch much better, since non-atomic really should die.
>>> Inflicting non-atomic on atomic helpers is bad imo, so nack from me on
>>> this patch here.
>>
>> I mostly agree, but we are in a transition period from non-atomic to
>> atomic. When all drivers have been converted to atomic, it should be
>> easy to grep for code using DRIVER_ATOMIC (or similar), and remove all
>> the non-atomic support code.
>>
>> In my opinion it should be considered case by case if the
>> non-atomic/atomic compat code should be added to the generic functions
>> or to all the drivers using that functionality.
>>
>> In this case, if it only affects tda998x (but does it?), perhaps the
>> patch in the link is better.
>
> Maybe we need a hybrid helper that just calls the atomic
> or non-atomic helper approppriately.
>

Would it actually be better if the legacy callback would automatically 
call atomic version if the driver has DRIVER_ATOMIC set?

I do not have any strong opinions on this, just as long as one of the 
patches gets merged. With quick grepping I can see that there are 
several DRM component drivers, but I have no idea if anything else but 
the tda998x is being used by more than one DRM master driver.

Best regards,
Jyri
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Re: [PATCH RFC] drm/atomic: Fall back to legacy call back in *_connector_dpms()

[Daniel Vetter]

On Mon, Feb 15, 2016 at 10:47 AM, Jyri Sarha <jsarha@ti.com> wrote:
> On 02/12/16 19:15, Ville Syrjälä wrote:
>>
>> On Fri, Feb 12, 2016 at 07:08:46PM +0200, Tomi Valkeinen wrote:
>>>
>>> On 12/02/16 17:34, Daniel Vetter wrote:
>>>>
>>>> On Fri, Feb 12, 2016 at 05:17:19PM +0200, Jyri Sarha wrote:
>>>>>
>>>>> Fall back to legacy drm_helper_connector_dpms() call back in
>>>>> drm_atomic_helper_connector_dpms() if DRIVER_ATOMIC feature is not
>>>>> present.
>>>>>
>>>>> Calling drm_atomic_helper_connector_dpms() from non atomic driver
>>>>> causes undefined behavior. This is a problem with componentized
>>>>> encoder/connector drivers that may be bound to both atomic and
>>>>> non atomic drivers.drm-next-tilcdc-fixes
>>>>>
>>>>> Signed-off-by: Jyri Sarha <jsarha@ti.com>
>>>>> ---
>>>>> This is just an alternative to this:
>>>>>
>>>>> https://lists.freedesktop.org/archives/dri-devel/2016-January/098867.html
>>>>
>>>>
>>>> I like the linked patch much better, since non-atomic really should die.
>>>> Inflicting non-atomic on atomic helpers is bad imo, so nack from me on
>>>> this patch here.
>>>
>>>
>>> I mostly agree, but we are in a transition period from non-atomic to
>>> atomic. When all drivers have been converted to atomic, it should be
>>> easy to grep for code using DRIVER_ATOMIC (or similar), and remove all
>>> the non-atomic support code.
>>>
>>> In my opinion it should be considered case by case if the
>>> non-atomic/atomic compat code should be added to the generic functions
>>> or to all the drivers using that functionality.
>>>
>>> In this case, if it only affects tda998x (but does it?), perhaps the
>>> patch in the link is better.
>>
>>
>> Maybe we need a hybrid helper that just calls the atomic
>> or non-atomic helper approppriately.
>>
>
> Would it actually be better if the legacy callback would automatically call
> atomic version if the driver has DRIVER_ATOMIC set?
>
> I do not have any strong opinions on this, just as long as one of the
> patches gets merged. With quick grepping I can see that there are several
> DRM component drivers, but I have no idea if anything else but the tda998x
> is being used by more than one DRM master driver.

I prefer open-coding since atomic vs. legacy is just one part of the
entire problem that the last element in the chain needs to register
the drm_connector, but in coordination with everyone else in the
chain. E.g. if you have upscale properties or anything else like that
it gets a lot more complicated, especially around the question of "who
owns drm_connector_state".

Given that I think it's better to add driver-private code for special
cases until we have a few examples and can go about creating a useful
helper library for this problem space. Instead of an inconsistent pile
of hacks enshrined forever.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch
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