On Sat, 12 Jul 2014 14:37:16 -0400
Rob Clark [off-list ref] wrote:

On Sat, Jul 12, 2014 at 2:16 PM, Boris BREZILLON
[off-list ref] wrote:

quoted

Hello,

On Mon,  7 Jul 2014 18:42:58 +0200
Boris BREZILLON [off-list ref] wrote:

quoted

+int atmel_hlcdc_layer_disable(struct atmel_hlcdc_layer *layer)
+{
+     struct atmel_hlcdc_layer_dma_channel *dma = &layer->dma;
+     unsigned long flags;
+     int i;
+
+     spin_lock_irqsave(&dma->lock, flags);
+     for (i = 0; i < layer->max_planes; i++) {
+             if (!dma->cur[i])
+                     break;
+
+             dma->cur[i]->ctrl = 0;
+     }
+     spin_unlock_irqrestore(&dma->lock, flags);
+
+     return 0;
+}

I'm trying to simplify the hlcdc_layer code and in order to do that I
need to know what's expected when a user calls plane_disable (or more
exactly DRM_IOCTL_MODE_SETPLANE ioctl call with the frame buffer ID set
to 0).

The HLCDC Display Controller support two types of disable:

1) The plane is disabled at the end of the current frame (the is the
solution I'm using)

2) The plane is disabled right away (I haven't tested it, but I think
this solution could generate some sort of artifacts for a short period
of time, because the framebuffer might be partially displayed)

If solution 1 is chosen, should I wait for the plane to be actually
disabled before returning ?

for cursor in particular, if you block, it is going to be a massive
slowdown for some apps.  I remember at least older gdm would rapidly
flash a spinning cursor.  As a result, if you wait for vsync each
time, it would take a couple minutes to login!

That makes sense.

if #2 works, I'd recommend it.  Otherwise you may have to do some of
the same hijinks that I have to do in mdp4_crtc for the cursor.

I already have a working solution which does not block with #1, I was
just trying to simplify my code ;-).
I'll try #2 and if it works without any side effects I'll go for it.

Thanks,

Boris

-- 
Boris Brezillon, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com