[PATCH] drm: vc4: Don't wait for vblank when updating the cursor

[Michel Dänzer]

On 01/03/17 11:00 AM, Michael Zoran wrote:
> On Wed, 2017-03-01 at 10:48 +0900, Michel Dänzer wrote:
>> On 01/03/17 12:45 AM, Michael Zoran wrote:
>>> On Tue, 2017-02-28 at 16:42 +0900, Michel Dänzer wrote:
>>>> On 24/02/17 10:54 AM, Michael Zoran wrote:
>>>>> Commonly used desktop environments such as xfce4 and gnome
>>>>> on debian sid can flood the graphics drivers with cursor
>>>>> updates.
>>>>
>>>> FWIW, this has nothing to do with the desktop environment or
>>>> indeed
>>>> the
>>>> client side at all. Translating input to HW cursor movement is
>>>> handled
>>>> entirely inside the X server.
>>>
>>> Yes, as your point out it may well be the x server that is causing
>>> this.  I wasn't sure if it was the windows manager or the x server
>>> that
>>> was doing this.
>>>
>>> Either way, when opening a new application the driver gets flooded
>>> with
>>> cursor updates as something is animating a spinning cursor.  Since
>>> the
>>> refresh rate is only 60Hz, I see a very long hang in the
>>> desktop(several minutes) where nothing responds.  SSHing into the
>>> RPI
>>> still works though even though it appears hung.
>>>
>>> I had a few people on the net test the changes and they all report
>>> that
>>> without the change xfce4 and gnome are both unusable on the
>>> RPI.  With
>>> the change, things work fine.  Not waiting for the vblank on cursor
>>> updates is what other drivers appears to do as well...
>>
>> Sure. My point is merely that the commit log should say "Xorg can
>> flood
>> [...]" instead of "Commonly used desktop environments such as xfce4
>> and
>> gnome on debian sid can flood [...]".
>>
> 
> Thanks for the tip.  I don't plan to submit many vc4 changes, but it's
> good to know.
> 
> BTW, you wouldn't happen to know what component is animating the
> spinning cursor?  I still highly suspect it's either the window
> manager(xfwm or mutter) or possibly the application that's drawing the
> taskbar.

A client asks the X server to use the spinning cursor, but the actual
animation and corresponding DRM_IOCTL_MODE_CURSOR(2) calls are performed
by the X server itself.


-- 
Earthling Michel Dänzer               |               http://www.amd.com
Libre software enthusiast             |             Mesa and X developer