Re: [PATCH v2 02/20] drm: Don't update plane properties for atomic planes if it stays the same

[Maarten Lankhorst <maarten.lankhorst@linux.intel.com>]

Op 08-07-15 om 10:55 schreef Daniel Vetter:
> On Wed, Jul 08, 2015 at 10:00:22AM +0200, Maarten Lankhorst wrote:
>> Op 07-07-15 om 18:43 schreef Daniel Vetter:
>>> On Tue, Jul 07, 2015 at 05:08:34PM +0200, Maarten Lankhorst wrote:
>>>> Op 07-07-15 om 14:10 schreef Daniel Vetter:
>>>>> On Tue, Jul 07, 2015 at 12:20:10PM +0200, Maarten Lankhorst wrote:
>>>>>> Op 07-07-15 om 11:18 schreef Daniel Vetter:
>>>>>>> On Tue, Jul 07, 2015 at 09:08:13AM +0200, Maarten Lankhorst wrote:
>>>>>>>> This allows the first atomic call during hw init to be a real modeset,
>>>>>>>> which is useful for forcing a recalculation.
>>>>>>> fbcon is optional, you can't rely on anything being done in any specific
>>>>>>> way. What exactly do you need this for, what's the implications?
>>>>>> In the hw readout I noticed some warnings when I wasn't setting any mode property in the readout.
>>>>>> I want the first function to be the modeset, so we have a sane base to commit changes on.
>>>>>> Ideally this whole function would have a atomic counterpart which does it in one go. :)
>>>>> Yeah. Otoh as soon as we have atomic modeset working we can replace all
>>>>> the legacy entry points with atomic helpers, and then even plane_disable
>>>>> will be a full atomic modeset.
>>>>>
>>>>> What did fall apart with just touching properties/planes now?
>>>> Also when i915 is fully atomic it calculates in intel_modeset_compute_config
>>>> if a modeset is needed after the first atomic call. Right now because
>>>> intel_modeset_compute_config is only called in set_config so this works as expected.
>>>> Otherwise drm_plane_force_disable or rotate_0 will force a modeset,
>>>> and if the final mode is different this will introduce a double modeset.
>>> For expensive properties (i.e. a no-op changes causes something that takes
>>> time like modeset or vblank wait) we need to make sure we filter them out
>>> in atomic_check. Yeah not quite there yet with pure atomic, but meanwhile
>>> the existing legacy set_prop functions should all filter out no-op changes
>>> themselves. If we don't do that for rotation then that's a bug.
>>>
>>> Same for disabling planes harder, that shouldn't take time. Especially
>>> since fbcon only force-disable non-primary plane, and for driver load
>>> that's the exact thing we already do in the driver anyway.
>> Something like this?
>> ---
>> diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
>> index a1d4e13f3908..2989232f4996 100644
>> --- a/drivers/gpu/drm/drm_atomic_helper.c
>> +++ b/drivers/gpu/drm/drm_atomic_helper.c
>> @@ -30,6 +30,7 @@
>>  #include <drm/drm_plane_helper.h>
>>  #include <drm/drm_crtc_helper.h>
>>  #include <drm/drm_atomic_helper.h>
>> +#include "drm_crtc_internal.h"
>>  #include <linux/fence.h>
>>  
>>  /**
>> @@ -1716,7 +1717,12 @@ drm_atomic_helper_crtc_set_property(struct drm_crtc *crtc,
>>  {
>>  	struct drm_atomic_state *state;
>>  	struct drm_crtc_state *crtc_state;
>> -	int ret = 0;
>> +	uint64_t retval;
>> +	int ret;
>> +
>> +	ret = drm_atomic_get_property(&crtc->base, property, &retval);
>> +	if (!ret && val == retval)
>> +		return 0;
>>  
>>  	state = drm_atomic_state_alloc(crtc->dev);
>>  	if (!state)
>> @@ -1776,7 +1782,12 @@ drm_atomic_helper_plane_set_property(struct drm_plane *plane,
>>  {
>>  	struct drm_atomic_state *state;
>>  	struct drm_plane_state *plane_state;
>> -	int ret = 0;
>> +	uint64_t retval;
>> +	int ret;
>> +
>> +	ret = drm_atomic_get_property(&plane->base, property, &retval);
>> +	if (!ret && val == retval)
>> +		return 0;
>>  
>>  	state = drm_atomic_state_alloc(plane->dev);
>>  	if (!state)
>> @@ -1836,7 +1847,12 @@ drm_atomic_helper_connector_set_property(struct drm_connector *connector,
>>  {
>>  	struct drm_atomic_state *state;
>>  	struct drm_connector_state *connector_state;
>> -	int ret = 0;
>> +	uint64_t retval;
>> +	int ret;
>> +
>> +	ret = drm_atomic_get_property(&connector->base, property, &retval);
>> +	if (!ret && val == retval)
>> +		return 0;
>>  
>>  	state = drm_atomic_state_alloc(connector->dev);
>>  	if (!state)
> The reason I didn't do this is that a prop change might still result in no
> hw state change (e.g. if you go automitic->explicit setting matching
> automatic one). Hence I think we need to solve this in lower levels
> anyway, i.e. in when computing the config. But it shouldn't cause trouble
> yet.
Is that a ack or nack?
>> diff --git a/drivers/gpu/drm/drm_crtc.c b/drivers/gpu/drm/drm_crtc.c
>> index 424c83323aaa..5bab7bff8a15 100644
>> --- a/drivers/gpu/drm/drm_crtc.c
>> +++ b/drivers/gpu/drm/drm_crtc.c
>> @@ -1327,7 +1327,8 @@ void drm_plane_force_disable(struct drm_plane *plane)
>>  {
>>  	int ret;
>>  
>> -	if (!plane->fb)
>> +	if ((plane->state && !plane->state->fb) ||
>> +	    (!plane->state && !plane->fb))
>>  		return;
> Nah, atomic helpers should figure this out imo. Since if userspace does
> the same (loop over all planes) then it won't go through force_disable.
> -Daniel
>
>>  
>>  	plane->old_fb = plane->fb;
>>

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