[PATCH v3] drm/tidss: dispc: Rewrite naive plane positioning code

[Jyri Sarha]

On 13/02/2020 13:52, Jyri Sarha wrote:
> On 13/02/2020 12:49, Tomi Valkeinen wrote:
>> On 13/02/2020 12:44, Jyri Sarha wrote:
>>
>>> +    /*
>>> +     * If a plane on a CRTC changes add all active planes on that
>>> +     * CRTC to the atomic state. This is needed for updating the
>>> +     * plane positions in tidss_crtc_position_planes() which is
>>> +     * called from crtc_atomic_enable() and crtc_atomic_flush().
>>> +     * The update is needed for x,y-position changes too, so
>>> +     * zpos_changed condition is not enough and we need this if
>>> +     * planes_changed is true too.
>>> +     */
>>> +    for_each_new_crtc_in_state(state, crtc, cstate, i) {
>>> +        if (cstate->zpos_changed || cstate->planes_changed) {
>>> +            ret = drm_atomic_add_affected_planes(state, crtc);
>>> +            if (ret)
>>> +                return ret;
>>> +        }
>>> +    }
>>
>> I think 99.99...% of the commits are such where only planes' fb address
>> is changed. I think "planes_changed" is true for these. I wonder if it
>> would be a sensible optimization to skip this for those 99.99...% cases.
>> Can we detect that easily?
>>
> 
> Sure by looping all planes in the state through with
> for_each_oldnew_plane_in_state() and checking if crtc_x or crtc_y has
> changed. But then again writing the positions of max 4 planes is really
> not that heavy operation. There is more calculation to do and more
> registers to write when updating the fp, so I do not think avoiding the
> OVR update justifies the extra complexity.
> 

Well, I implemented this anyway just for the fun of it. After all the
added complexity is not that much, since we already have an extended
CRTC state. Judge your self, I'll send v4 shortly.

Best regards,
Jyri

>> Well, we haven't optimized for those 99.99...% cases anywhere else
>> either, so it's possible it doesn't matter.
>>
> 
> 
> 
> 
> 


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